知識和信仰 -- 再談「演化論」
我同意小河和Deep Purple兩位網友的意見(小河 2007，Deep Purple 2007)：
任何「科學理論」都必須通過能否解釋其所試圖解釋現象這個檢驗；它也必須通過觀察到的自然現象是否符合此理論所「預測」的相關發展或結果。這就是BigA網友所說的" tested and proved/disproved"。如果一個「科學理論」不能通過這兩個檢驗，它就被「反證」；也就會緊接著被修正、取代、或拋棄。
一個「科學理論」的價值，在它的解釋能力和範圍。我相信「演化論」的解釋能力和範圍，是絕大多數科學家都接受和肯定的。不需要我們這些外行人在此爭論(Ehrlich 2002, Zimmer 2002, McFadden 2002)。
有些學者從理論上不接受達爾文和當代「演化論」的假設、推論、和對化石記錄或生物結構變化原因的詮釋。他們也主張某種intelligence design的理論。但這和基本教義派的intelligence design或其前身creationism並沒有直接關係。後者可能引用前者的論述來玩他/她們的障眼法或帽子遊戲。
3.4 Michael Cremo
有一位接受印度哲學的Michael Cremo。他寫了一本批評「演化論」的書(Forbidden Archeology )。他批評的是古典「演化論」和一些誤用「演化論」的詮釋或論述(Tarzia 2007)。他的批評或攻擊和當代「演化論」的內容並不相關。
法輪功的網站也刊登許多大肆攻擊「演化論」的文章。我實在想不出李洪志撈過界或漟這個混水的理由。我合理懷疑他拿了美國極右派的錢。而美國極右派通常和基本教義派的領導人掛勾，如Monicas 網友介紹的The Discovery Institute、ARN、和ISCID這些團體或所謂的Think Tank。因此，法輪功也在自己的文宣機器上配合這方面的「意識型態」散播。
... It is a result of environmental change which favors organisms to come up with a new approach to deal with problems.
... It is a result of genetic change which happens randomly, but which happens to endow the newly constituted organism to have a favorable chance for survival in the environmental niche that it happens to occupy.
* BigA 2007，《進化論的破滅》留言4和6，中時電子報 >> 【新聞對談】，http://tb.chinatimes.com/forum1.asp?ArticleID=997404
* Deep Purple 2007，《進化論的破滅》留言8和10，中時電子報 >> 【新聞對談】，http://tb.chinatimes.com/forum1.asp?ArticleID=997404
* Ehrlich, P. R. 2002, Human Nature: Genes, Culture, and the Human Prospect, Penguin Books, NYC
* McFadden, J. 2002, Quantum Evolution, How Physics' Weirdest Theory Explains Life's Biggest Mystery, W. W. Norton & Company, NYC
* Tarzia, W. 2007, Forbidden Archaeology : Antievolutionism Outside the Christian Arena, http://www.ramtops.co.uk/tarzia.html
* Zimmer, C. 2002, Evolution: The Triumph of An Idea, Harper Collins Publishers, NYC
*小河 2007，《進化論的破滅》留言1，中時電子報 >> 【新聞對談】，http://tb.chinatimes.com/forum1.asp?ArticleID=997404
本文原載：中時電子報 >> 【新聞對談】 >> 《知識對談》。留言123
本文於 修改第 4 次
10個說明生命演化過程的化石 – S. Levingston
How these 10 fossils explain life on Earth
Fossils unlock the evolution of life on Earth, revealing our path from mere microscopic filaments to upright humans. Here’s a quick journey through the ages as told in 10 fossils, adapted from “A History of Life in 100 Fossils” by Paul D. Taylor and Aaron O’Dea (Smithsonian Books, $34.95).
1. Apex Chert
These – the world’s oldest fossils – are estimated to be about 3.465 billion years old. But are they truly fossils? Found in Western Australia in a glassy rock called the Apex Chert, they are made up of microscopic filaments that some scientists believe are nothing more than non-biological, inorganic structures. But others argue the fossils are bits of bacteria, which is consistent with chemical evidence, suggesting that life on Earth did in fact exist 3.5 billion years ago.
2. Doushantuo fossils
Between 560 million and 580 million years old, the Doushantuo Formation in China is remarkable because it preserves a rare example of animals without a hard skeleton. These beautifully preserved fossils of soft-bodied organisms astonishingly resemble early embryos of some modern animals.
Small plants like Cooksonia made the evolutionary leap from the seas to the land four hundred million years ago and dominated the landscape for 40 million years. They set the stage for more complex plants -- and eventually the arrival of terrestrial animals -- by stabilizing the soil and oxygenating the atmosphere.
Another momentous leap from sea to land was the evolution of fish into tetrapods, or four-legged land-dwelling creatures like amphibians, reptiles, birds, and mammals. Eusthenopteron is an important link in this evolution. It is a fish whose fins are joined to the body by a single bone, a bone that is the equivalent of the limbs found in tetrapods, and it was the tetrapods that spread out across the land, ultimately laying the foundation for the evolution of humans.
Though it looks like a dinosaur, Dimetrodon lived 50 million years before the first dinosaurs walked the Earth. It was closely related to the therapsids, the branch of land vertebrates that included the precursors of all mammals.
Plesiosaura were reptiles with long necks and flipper-like paddles, and they disappeared about 70 million years ago. Their necks were so long and heavy they could never have come out of the water – they needed the buoyancy of water to manage their necks. And here’s a shocker: the Loch Ness monster was not a plesiosaur, despite what an article in the journal Nature suggested in 1975 because, with its insupportable neck, it could not have traveled over land to reach the Loch.
Archaeopteryx is widely hailed as the perfect evolutionary link between birds and reptiles. Some of its features are birdlike (wings, feathers, and a wishbone) while others are reptilian (teeth, a bony tail, and claws on its hands). Therefore this creature shows us a possible connection or continuity between two groups of animals that appear to be so different.
A fisherman made a shocking discovery in 1938: he pulled out of the sea a living coelacanth -- a member of a group of fishes that was until then known only from the fossil record, spanning from 70 million to 400 million years ago and presumed to have gone extinct along with the dinosaurs. This “biological find of the century” revealed not only that coelacanths remained relatively unchanged for 400 million years but starkly illustrated how little we know about life in the world’s oceans today.
9. Laetoli footprints
This series of tracks, perfectly preserved by the ashes from an ancient Tanzanian volcano, include some unmistakably hominin tracks. They depict three individuals traveling in the same direction. We know these to be made by an early human because the feet had a big toe in line with the foot (as opposed to ape feet with splayed toes useful for climbing trees) and the heels dug deeper than the toes, implying a fully upright style of walking. These trace fossils are a record of active life with a connection to us.
10. Homo heidelbergensis
Homo heidelbergensis, like this example found in Africa in 1921, is estimated to be between 200,000 and 300,000 years old. Although undeniably human in general appearance, the skull has a huge face and eyebrow ridges, as well as a low forehead. Scientists estimate that Homo heidelbergensis would have had a stature close to that of modern humans, with a skull capacity allowing for a brain only about 14 percent lighter than that of the average modern human. This find has particular importance in human evolution, as many scientists interpret it as the last ancestor of modern humans.
First ever evidence of a swimming, shark-eating dinosaur
Newly discovered dinosaur, Dreadnoughtus
The T. rex that got away
Steven Levingston is the nonfiction editor of The Washington Post. He is author of “Little Demon in the City of Light: A True Story of Murder and Mesmerism in Belle Époque Paris” (Doubleday, 2014) and “The Kennedy Baby: The Loss that Transformed JFK” (Washington Post eBook, 2013).
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演化論需要新思考方向嗎？ - Kevin Laland等
Does evolutionary theory need a rethink?
YES, URGENTLY -- Kevin Laland and colleagues
NO, ALL IS WELL -- Gregory A. Wray, Hopi E. Hoekstra and colleagues
Researchers are divided over what processes should be considered fundamental.
Kevin Laland1, Tobias Uller7, Marc Feldman8, Kim Sterelny9, Gerd B. Müller10, ArminMoczek11, Eva Jablonka12, John Odling-Smee13, Gregory A. Wray3, Hopi E. Hoekstra5, Douglas J. Futuyma14, Richard E. Lenski15, Trudy F. C. Mackay16, Dolph Schluter17 & Joan E. Strassmann, 10/08/14
Does evolutionary theory need a rethink? Yes, urgently
Without an extended evolutionary framework, the theory neglects key processes, say Kevin Laland and colleagues.
Charles Darwin conceived of evolution by natural selection without knowing that genes exist. Now mainstream evolutionary theory has come to focus almost exclusively on genetic inheritance and processes that change gene frequencies.
Yet new data pouring out of adjacent fields are starting to undermine this narrow stance. An alternative vision of evolution is beginning to crystallize, in which the processes by which organisms grow and develop are recognized as causes of evolution.
Some of us first met to discuss these advances six years ago. In the time since, as members of an interdisciplinary team, we have worked intensively to develop a broader framework, termed the extended evolutionary synthesis1 (EES), and to flesh out its structure, assumptions and predictions. In essence, this synthesis maintains that important drivers of evolution, ones that cannot be reduced to genes, must be woven into the very fabric of evolutionary theory.
We believe that the EES will shed new light on how evolution works. We hold that organisms are constructed in development, not simply ‘programmed’ to develop by genes. Living things do not evolve to fit into pre-existing environments, but co-construct and coevolve with their environments, in the process changing the structure of ecosystems.
The number of biologists calling for change in how evolution is conceptualized is growing rapidly. Strong support comes from allied disciplines, particularly developmental biology, but also genomics, epigenetics, ecology and social science1, 2. We contend that evolutionary biology needs revision if it is to benefit fully from these other disciplines. The data supporting our position gets stronger every day.
Yet the mere mention of the EES often evokes an emotional, even hostile, reaction among evolutionary biologists. Too often, vital discussions descend into acrimony, with accusations of muddle or misrepresentation. Perhaps haunted by the spectre of intelligent design, evolutionary biologists wish to show a united front to those hostile to science. Some might fear that they will receive less funding and recognition if outsiders -- such as physiologists or developmental biologists -- flood into their field.
However, another factor is more important: many conventional evolutionary biologists study the processes that we claim are neglected, but they comprehend them very differently (see ‘No, all is well’). This is no storm in an academic tearoom, it is a struggle for the very soul of the discipline.
Here we articulate the logic of the EES in the hope of taking some heat out of this debate and encouraging open discussion of the fundamental causes of evolutionary change (see Supplementary Information).
The core of current evolutionary theory was forged in the 1930s and 1940s. It combined natural selection, genetics and other fields into a consensus about how evolution occurs. This ‘modern synthesis’ allowed the evolutionary process to be described mathematically as frequencies of genetic variants in a population change over time -- as, for instance, in the spread of genetic resistance to the myxoma virus in rabbits.
In the decades since, evolutionary biology has incorporated developments consistent with the tenets of the modern synthesis. One such is ‘neutral theory’, which emphasizes random events in evolution. However, standard evolutionary theory (SET) largely retains the same assumptions as the original modern synthesis, which continues to channel how people think about evolution.
The story that SET tells is simple: new variation arises through random genetic mutation; inheritance occurs through DNA; and natural selection is the sole cause of adaptation, the process by which organisms become well-suited to their environments. In this view, the complexity of biological development -- the changes that occur as an organism grows and ages -- are of secondary, even minor, importance.
In our view, this ‘gene-centric’ focus fails to capture the full gamut of processes that direct evolution. Missing pieces include how physical development influences the generation of variation (developmental bias); how the environment directly shapes organisms’ traits (plasticity); how organisms modify environments (niche construction); and how organisms transmit more than genes across generations (extra-genetic inheritance). For SET, these phenomena are just outcomes of evolution. For the EES, they are also causes.
Valuable insight into the causes of adaptation and the appearance of new traits comes from the field of evolutionary developmental biology (‘evo-devo’). Some of its experimental findings are proving tricky to assimilate into SET. Particularly thorny is the observation that much variation is not random because developmental processes generate certain forms more readily than others3. For example, among one group of centipedes, each of the more than 1,000 species has an odd number of leg-bearing segments, because of the mechanisms of segment development3.
In our view, this concept -- developmental bias -- helps to explain how organisms adapt to their environments and diversify into many different species. For example, cichlid fishes in Lake Malawi are more closely related to other cichlids in Lake Malawi than to those in Lake Tanganyika, but species in both lakes have strikingly similar body shapes4. In each case, some fish have large fleshy lips, others protruding foreheads, and still others short, robust lower jaws.
SET explains such parallels as convergent evolution: similar environmental conditions select for random genetic variation with equivalent results. This account requires extraordinary coincidence to explain the multiple parallel forms that evolved independently in each lake. A more succinct hypothesis is that developmental bias and natural selection work together4, 5. Rather than selection being free to traverse across any physical possibility, it is guided along specific routes opened up by the processes of development5, 6.
“There is more to inheritance than genes.”
Another kind of developmental bias occurs when individuals respond to their environment by changing their form -- a phenomenon called plasticity. For instance, leaf shape changes with soil water and chemistry. SET views this plasticity as merely fine-tuning, or even noise. The EES sees it as a plausible first step in adaptive evolution. The key finding here is that plasticity not only allows organisms to cope in new environmental conditions but to generate traits that are well-suited to them. If selection preserves genetic variants that respond effectively when conditions change, then adaptation largely occurs by accumulation of genetic variations that stabilize a trait after its first appearance5, 6. In other words, often it is the trait that comes first; genes that cement it follow, sometimes several generations later5.
Studies of fish, birds, amphibians and insects suggest that adaptations that were, initially, environmentally induced may promote colonization of new environments and facilitate speciation5, 6. Some of the best-studied examples of this are in fishes, such as sticklebacks and Arctic char. Differences in the diets and conditions of fish living at the bottom and in open water have induced distinct body forms, which seem to be evolving reproductive isolation, a stage in forming new species. The number of species in a lineage does not depend solely on how random genetic variation is winnowed through different environmental sieves. It also hangs on developmental properties that contribute to the lineage’s ‘evolvability’.
In essence, SET treats the environment as a ‘background condition’, which may trigger or modify selection, but is not itself part of the evolutionary process. It does not differentiate between how termites become adapted to mounds that they construct and, say, how organisms adapt to volcanic eruptions. We view these cases as fundamentally different7.
Volcanic eruptions are idiosyncratic events, independent of organisms’ actions. By contrast, termites construct and regulate their homes in a repeatable, directional manner that is shaped by past selection and that instigates future selection. Similarly, mammals, birds and insects defend, maintain and improve their nests -- adaptive responses to nest building that have evolved again and again7. This ‘niche construction’, like developmental bias, means that organisms co-direct their own evolution by systematically changing environments and thereby biasing selection7.
Inheritance beyond genes
SET has long regarded inheritance mechanisms outside genes as special cases; human culture being the prime example. The EES explicitly recognizes that parent–offspring similarities result in part from parents reconstructing their own developmental environments for their offspring. ‘Extra-genetic inheritance’ includes the transmission of epigenetic marks (chemical changes that alter DNA expression but not the underlying sequence) that influence fertility, longevity and disease resistance across taxa8. In addition, extra-genetic inheritance includes socially transmitted behaviour in animals, such as nut cracking in chimpanzees or the migratory patterns of reef fishes8, 9. It also encompasses those structures and altered conditions that organisms leave to their descendants through their niche construction -- from beavers’ dams to worm-processed soils7, 10. Research over the past decade has established such inheritance to be so widespread that it should be part of general theory.
Mathematical models of evolutionary dynamics that incorporate extra-genetic inheritance make different predictions from those that do not7–9. Inclusive models help to explain a wide range of puzzling phenomena, such as the rapid colonization of North America by the house finch, the adaptive potential of invasive plants with low genetic diversity, and how reproductive isolation is established.
Such legacies can even generate macro-evolutionary patterns. For instance, evidence suggests that sponges oxygenated the ocean and by doing so created opportunities for other organisms to live on the seabed10. Accumulating fossil data indicate that inherited modifications of the environment by species has repeatedly facilitated, sometimes after millions of years, the evolution of new species and ecosystems10.
The above insights derive from different fields, but fit together with surprising coherence. They show that variation is not random, that there is more to inheritance than genes, and that there are multiple routes to the fit between organisms and environments. Importantly, they demonstrate that development is a direct cause of why and how adaptation and speciation occur, and of the rates and patterns of evolutionary change.
SET consistently frames these phenomena in a way that undermines their significance. For instance, developmental bias is generally taken to impose ‘constraints’ on what selection can achieve -- a hindrance that explains only the absence of adaptation. By contrast, the EES recognizes developmental processes as a creative element, demarcating which forms and features evolve, and hence accounting for why organisms possess the characters that they do.
Researchers in fields from physiology and ecology to anthropology are running up against the limiting assumptions of the standard evolutionary framework without realizing that others are doing the same. We believe that a plurality of perspectives in science encourages development of alternative hypotheses, and stimulates empirical work. No longer a protest movement, the EES is now a credible framework inspiring useful work by bringing diverse researchers under one theoretical roof to effect conceptual change in evolutionary biology.
Does evolutionary theory need a rethink? No, all is well
Theory accommodates evidence through relentless synthesis, say Gregory A. Wray, Hopi E. Hoekstra and colleagues.
In October 1881, just six months before he died, Charles Darwin published his final book. The Formation of Vegetable Mould, Through the Actions of Worms11 sold briskly: Darwin’s earlier publications had secured his reputation. He devoted an entire book to these humble creatures in part because they exemplify an interesting feedback process: earthworms are adapted to thrive in an environment that they modify through their own activities.
Darwin learned about earthworms from conversations with gardeners and his own simple experiments. He had a genius for distilling penetrating insights about evolutionary processes -- often after amassing years of observational and experimental data -- and he drew on such disparate topics as agriculture, geology, embryology and behaviour. Evolutionary thinking ever since has followed Darwin’s lead in its emphasis on evidence and in synthesizing information from other fields.
A profound shift in evolutionary thinking began during the 1920s, when a handful of statisticians and geneticists began quietly laying the foundations for a dramatic transformation. Their work between 1936 and 1947 culminated in the ‘modern synthesis’, which united Darwin’s concept of natural selection with the nascent field of genetics and, to a lesser extent, palaeontology and systematics. Most importantly, it laid the theoretical foundations for a quantitative and rigorous understanding of adaptation and speciation, two of the most fundamental evolutionary processes.
In the decades since, generations of evolutionary biologists have modified, corrected and extended the framework of the modern synthesis in countless ways. Like Darwin, they have drawn heavily from other fields. When molecular biologists identified DNA as the material basis for heredity and trait variation, for instance, their discoveries catalysed fundamental extensions to evolutionary theory. For example, the realization that many genetic changes have no fitness consequences led to major theoretical advances in population genetics. The discovery of ‘selfish’ DNA prompted discussions about selection at the level of genes rather than traits. Kin selection theory, which describes how traits affecting relatives are selected, represents another extension12.
Nonetheless there are evolutionary biologists (see ‘Yes, urgently’) who argue that theory has since ossified around genetic concepts. More specifically, they contend that four phenomena are important evolutionary processes: phenotypic plasticity, niche construction, inclusive inheritance and developmental bias. We could not agree more. We study them ourselves.
But we do not think that these processes deserve such special attention as to merit a new name such as ‘extended evolutionary synthesis’. Below we outline three reasons why we believe that these topics already receive their due in current evolutionary theory.
New words, old concepts
The evolutionary phenomena championed by Laland and colleagues are already well integrated into evolutionary biology, where they have long provided useful insights. Indeed, all of these concepts date back to Darwin himself, as exemplified by his analysis of the feedback that occurred as earthworms became adapted to their life in soil.
Today we call such a process niche construction, but the new name does not alter the fact that evolutionary biologists have been studying feedback between organisms and the environment for well over a century13. Stunning adaptations such as termite mounds, beaver dams, and bowerbird displays have long been a staple of evolutionary studies. No less spectacular are cases that can only be appreciated at the microscopic or molecular scale, such as viruses that hijack host cells to reproduce and ‘quorum sensing’, a sort of group think by bacteria.
Another process, phenotypic plasticity, has drawn considerable attention from evolutionary biologists. Countless cases in which the environment influences trait variation have been documented -- from the jaws of cichlid fishes that change shape when food sources alter, to leaf-mimicking insects that are brown if born in the dry season and green in the wet. Technological advances in the past decade have revealed an incredible degree of plasticity in gene expression in response to diverse environmental conditions, opening the door to understanding its material basis. Much discussed, too, was a book5 by behavioural scientist Mary Jane West-Eberhard that explored how plasticity might precede genetic changes during adaptation.
So, none of the phenomena championed by Laland and colleagues are neglected in evolutionary biology. Like all ideas, however, they need to prove their value in the marketplace of rigorous theory, empirical results and critical discussion. The prominence that these four phenomena command in the discourse of contemporary evolutionary theory reflects their proven explanatory power, not a lack of attention.
Furthermore, the phenomena that interest Laland and colleagues are just four among many that offer promise for future advances in evolutionary biology. Most evolutionary biologists have a list of topics that they would like to see given more attention. Some would argue that epistasis -- complex interactions among genetic variants -- has long been under-appreciated. Others would advocate for cryptic genetic variation (mutations that affect only traits under specific genetic or environmental conditions). Still others would stress the importance of extinction, or adaptation to climate change, or the evolution of behaviour. The list goes on.
We could stop and argue about whether ‘enough’ attention is being paid to any of these. Or we could roll up our sleeves, get to work, and find out by laying the theoretical foundations and building a solid casebook of empirical studies. Advocacy can take an idea only so far.
What Laland and colleagues term the standard evolutionary theory is a caricature that views the field as static and monolithic. They see today’s evolutionary biologists as unwilling to consider ideas that challenge convention.
We see a very different world. We consider ourselves fortunate to live and work in the most exciting, inclusive and progressive period of evolutionary research since the modern synthesis. Far from being stuck in the past, current evolutionary theory is vibrantly creative and rapidly growing in scope. Evolutionary biologists today draw inspiration from fields as diverse as genomics, medicine, ecology, artificial intelligence and robotics. We think Darwin would approve.
Genes are central
Finally, diluting what Laland and colleagues deride as a ‘gene-centric’ view would de-emphasize the most powerfully predictive, broadly applicable and empirically validated component of evolutionary theory. Changes in the hereditary material are an essential part of adaptation and speciation. The precise genetic basis for countless adaptations has been documented in detail, ranging from antibiotic resistance in bacteria to camouflage coloration in deer mice, to lactose tolerance in humans.
Although genetic changes are required for adaptation, non-genetic processes can sometimes play a part in how organisms evolve. Laland and colleagues are correct that phenotypic plasticity, for instance, may contribute to the adaptedness of an individual. A seedling might bend towards brighter light, growing into a tree with a different shape from its siblings’. Many studies have shown that this kind of plasticity is beneficial, and that it can readily evolve if there is genetic variation in the response14. This role for plasticity in evolutionary change is so well documented that there is no need for special advocacy.
“What matters is the heritable differences in traits, especially those that bestow some selective advantage.”
Much less clear is whether plasticity can ‘lead’ genetic variation during adaptation. More than half a century ago, developmental biologist Conrad Waddington described a process that he called genetic assimilation15. Here, new mutations can sometimes convert a plastic trait into one that develops even without the specific environmental condition that originally induced it. Few cases have been documented outside of the laboratory, however. Whether this is owing to a lack of serious attention or whether it reflects a genuine rarity in nature can be answered only by further study.
Lack of evidence also makes it difficult to evaluate the role that developmental bias may have in the evolution (or lack of evolution) of adaptive traits. Developmental processes, based on features of the genome that may be specific to a particular group of organisms, certainly can influence the range of traits that natural selection can act on. However, what matters ultimately is not the extent of trait variation, nor even its precise mechanistic causes. What matters is the heritable differences in traits, especially those that bestow some selective advantage. Likewise, there is little evidence for the role of inherited epigenetic modification (part of what was termed ‘inclusive inheritance’) in adaptation: we know of no case in which a new trait has been shown to have a strictly epigenetic basis divorced from gene sequence. On both topics, further research will be valuable.
All four phenomena that Laland and colleagues promote are ‘add-ons’ to the basic processes that produce evolutionary change: natural selection, drift, mutation, recombination and gene flow. None of these additions is essential for evolution, but they can alter the process under certain circumstances. For this reason they are eminently worthy of study.
We invite Laland and colleagues to join us in a more expansive extension, rather than imagining divisions that do not exist. We appreciate their ideas as an important part of what evolutionary theory might become in the future. We, too, want an extended evolutionary synthesis, but for us, these words are lowercase because this is how our field has always advanced16.
The best way to elevate the prominence of genuinely interesting phenomena such as phenotypic plasticity, inclusive inheritance, niche construction and developmental bias (and many, many others) is to strengthen the evidence for their importance.
Before claiming that earthworms “have played a more important part in the history of the world than most persons would at first suppose”11, Darwin collected more than 40 years of data. Even then, he published only for fear that he would soon be “joining them”17.
Journal name: Nature
Date published: (09 October 2014)
1. Pigliucci, M. & Müller, G. B. Evolution: The Extended Synthesis (MIT Press, 2010).
2. Noble, D. et al. J. Physiol. 592, 2237–2244 (2014).
3. Arthur, W. Biased Embryos and Evolution (Cambridge Univ. Press, 2004).
4. Brakefield, P. M. Trends Ecol. Evol. 21, 362–368 (2006).
5. West-Eberhard, M. J. Developmental Plasticity and Evolution (Oxford Univ. Press, 2003).
6. Pfennig, D. W. et al. Trends Ecol. Evol. 25, 459–467 (2010).
7. Odling-Smee, F. J., Laland, K. N. & Feldman, M. W. Niche Construction: The Neglected Process in Evolution (Princeton Univ. Press, 2003).
8. Jablonka, E. & Lamb, M. Evolution in Four Dimensions: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life (MIT Press, 2014).
9. Hoppitt, W. & Laland, K. N. Social Learning: An Introduction to Mechanisms, Methods, and Models (Princeton Univ. Press, 2013).
10. Erwin, D. H. & Valentine J. W. The Cambrian Explosion: The Construction of Animal Biodiversity (Roberts, 2013).
11. Darwin, C. The Formation of Vegetable Mould, Through the Actions of Worms (John Murray, 1881).
12. Alcock, J. The Triumph of Sociobiology (Oxford Univ. Press, 2001).
13. Bailey, N. W. Trends Ecol. Evol. 27, 561–569 (2012).
14. Wada, H. & Sewall, K. B. Integ. Comp. Biol. http://dx.doi.org/10.1093/icb/icu097 (2014).
15. Waddington, C. H. Nature 150, 563–565 (1942).
16. Callebaut, W. in Evolution: The Extended Synthesis (Pigliucci, M. & Müller, G. B. eds) 443–482 (MIT Press, 2010).
17. Browne, J. Charles Darwin: The Power of Place Vol. II 479 (Jonathan Cape, 2003).
Related stories and links
1. Kevin Laland is professor of behavioural and evolutionary biology at the University of St Andrews, UK
2. Gregory A. Wray is professor of biology at Duke University in Durham, North Carolina, USA
3. Hopi E. Hoekstra is professor of biology at Harvard University in Cambridge, Massachusetts, USA
4. Tobias Uller is in the Department of Zoology, University of Oxford, UK, and the Department of Biology at Lund University, Sweden.
5. Marc Feldman is in the Department of Biology, Herrin Hall, Stanford University, California, USA
6. Kim Sterelny is at the School of Philosophy, Australian National University, Canberra, Australia, and the School of History, Philosophy, Political Science and International Relations, Victoria University of Wellington, New Zealand
7. Gerd B. Müller is in the Department of Theoretical Biology, University of Vienna, Austria
8. Armin Moczek is in the Department of Biology, Indiana University, Bloomington, Indiana, USA
9. Eva Jablonka is at the Cohn Institute for the History of Philosophy of Science and Ideas, Tel Aviv University, Israel
10. John Odling-Smee is at Mansfield College, University of Oxford, UK
11. Douglas J. Futuyma is in the Department of Ecology and Evolution at Stony Brook University in Stony Brook, New York, USA
12. Richard E. Lenski is in the Department of Microbiology and Molecular Genetics at Michigan State University in East Lansing, Michigan, USA
13. Trudy F. C. Mackay is in the Department of Genetics at North Carolina State University in Raleigh, North Carolina, USA
14. Dolph Schluter is in the Department of Zoology at the University of British Columbia in Vancouver, British Columbia, Canada
15. Joan E. Strassmann is in the Department of Biology at Washington University in St Louis, Missouri, USA
· Kevin Laland,
· Gregory A. Wray
· or Hopi E. Hoekstra
1. Supplementary information (1.2M)
· Evolution: How the unicorn got its horn
· Beyond DNA: integrating inclusive inheritance into an extended theory of evolution
· Biological theory: Postmodern evolution?
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演化過程可能會殊途同歸嗎？ - E. Singer
Evolution’s Random Paths Lead to One Place
A massive statistical study suggests that the final evolutionary outcome — fitness — is predictable.
Emily Singer, 09/11/14
In his fourth-floor lab at Harvard University, Michael Desai has created hundreds of identical worlds in order to watch evolution at work. Each of his meticulously controlled environments is home to a separate strain of baker’s yeast. Every 12 hours, Desai’s robot assistants pluck out the fastest-growing yeast in each world — selecting the fittest to live on — and discard the rest. Desai then monitors the strains as they evolve over the course of 500 generations. His experiment, which other scientists say is unprecedented in scale, seeks to gain insight into a question that has long bedeviled biologists: If we could start the world over again, would life evolve the same way?
Many biologists argue that it would not, that chance mutations early in the evolutionary journey of a species will profoundly influence its fate. “If you replay the tape of life, you might have one initial mutation that takes you in a totally different direction,” Desai said, paraphrasing an idea first put forth by the biologist Stephen Jay Gould in the 1980s.
Desai’s yeast cells call this belief into question. According to results published in Science in June, all of Desai’s yeast varieties arrived at roughly the same evolutionary endpoint (as measured by their ability to grow under specific lab conditions) regardless of which precise genetic path each strain took. It’s as if 100 New York City taxis agreed to take separate highways in a race to the Pacific Ocean, and 50 hours later they all converged at the Santa Monica pier.
The findings also suggest a disconnect between evolution at the genetic level and at the level of the whole organism. Genetic mutations occur mostly at random, yet the sum of these aimless changes somehow creates a predictable pattern. The distinction could prove valuable, as much genetics research has focused on the impact of mutations in individual genes. For example, researchers often ask how a single mutation might affect a microbe’s tolerance for toxins, or a human’s risk for a disease. But if Desai’s findings hold true in other organisms, they could suggest that it’s equally important to examine how large numbers of individual genetic changes work in concert over time.
“There’s a kind of tension in evolutionary biology between thinking about individual genes and the potential for evolution to change the whole organism,” said Michael Travisano, a biologist at the University of Minnesota. “All of biology has been focused on the importance of individual genes for the last 30 years, but the big take-home message of this study is that’s not necessarily important.”
The key strength in Desai’s experiment is its unprecedented size, which has been described by others in the field as “audacious.” The experiment’s design is rooted in its creator’s background; Desai trained as a physicist, and from the time he launched his lab four years ago, he applied a statistical perspective to biology. He devised ways to use robots to precisely manipulate hundreds of lines of yeast so that he could run large-scale evolutionary experiments in a quantitative way. Scientists have long studied the genetic evolution of microbes, but until recently, it was possible to examine only a few strains at a time. Desai’s team, in contrast, analyzed 640 lines of yeast that had all evolved from a single parent cell. The approach allowed the team to statistically analyze evolution.
“This is the physicist’s approach to evolution, stripping down everything to the simplest possible conditions,” said Joshua Plotkin, an evolutionary biologist at the University of Pennsylvania who was not involved in the research but has worked with one of the authors. “They could partition how much of evolution is attributable to chance, how much to the starting point, and how much to measurement noise.”
Desai’s plan was to track the yeast strains as they grew under identical conditions and then compare their final fitness levels, which were determined by how quickly they grew in comparison to their original ancestral strain. The team employed specially designed robot arms to transfer yeast colonies to a new home every 12 hours. The colonies that had grown the most in that period advanced to the next round, and the process repeated for 500 generations. Sergey Kryazhimskiy, a postdoctoral researcher in Desai’s lab, sometimes spent the night in the lab, analyzing the fitness of each of the 640 strains at three different points in time. The researchers could then compare how much fitness varied among strains, and find out whether a strain’s initial capabilities affected its final standing. They also sequenced the genomes of 104 of the strains to figure out whether early mutations changed the ultimate performance.
Previous studies have indicated that small changes early in the evolutionary journey can lead to big differences later on, an idea known as historical contingency. Long-term evolution studies in E. coli bacteria, for example, found that the microbes can sometimes evolve to eat a new type of food, but that such substantial changes only happen when certain enabling mutations happen first. These early mutations don’t have a big effect on their own, but they lay the necessary groundwork for later mutations that do.
But because of the small scale of such studies, it wasn’t clear to Desai whether these cases were the exception or the rule. “Do you typically get big differences in evolutionary potential that arise in the natural course of evolution, or for the most part is evolution predictable?” he said. “To answer this we needed the large scale of our experiment.”
As in previous studies, Desai found that early mutations influence future evolution, shaping the path the yeast takes. But in Desai’s experiment, that path didn’t affect the final destination. “This particular kind of contingency actually makes fitness evolution more predictable, not less,” Desai said.
Desai found that just as a single trip to the gym benefits a couch potato more than an athlete, microbes that started off growing slowly gained a lot more from beneficial mutations than their fitter counterparts that shot out of the gate. “If you lag behind at the beginning because of bad luck, you’ll tend to do better in the future,” Desai said. He compares this phenomenon to the economic principle of diminishing returns — after a certain point, each added unit of effort helps less and less.
Scientists don’t know why all genetic roads in yeast seem to arrive at the same endpoint, a question that Desai and others in the field find particularly intriguing. The yeast developed mutations in many different genes, and scientists found no obvious link among them, so it’s unclear how these genes interact in the cell, if they do at all. “Perhaps there is another layer of metabolism that no one has a handle on,” said Vaughn Cooper, a biologist at the University of New Hampshire who was not involved in the study.
It’s also not yet clear whether Desai’s carefully controlled results are applicable to more complex organisms or to the chaotic real world, where both the organism and its environment are constantly changing. “In the real world, organisms get good at different things, partitioning the environment,” Travisano said. He predicts that populations within those ecological niches would still be subject to diminishing returns, particularly as they undergo adaptation. But it remains an open question, he said.
Nevertheless, there are hints that complex organisms can also quickly evolve to become more alike. A study published in May analyzed groups of genetically distinct fruit flies as they adapted to a new environment. Despite traveling along different evolutionary trajectories, the groups developed similarities in attributes such as fecundity and body size after just 22 generations. “I think many people think about one gene for one trait, a deterministic way of evolution solving problems,” said David Reznick, a biologist at the University of California, Riverside. “This says that’s not true; you can evolve to be better suited to the environment in many ways.”
Desai’s study isn’t the first to suggest that the law of diminishing returns applies to evolution. A famous decades-long experiment from Richard Lenski’s lab at Michigan State University, which has tracked E. coli for thousands of generations, found that fitness converged over time. But because of limitations in genomics technology in the 1990s, that study didn’t identify the mutations underlying those changes. “The 36 populations we had then would have been much more expensive to sequence than the hundred they did here,” said Michael Travisano of the University of Minnesota, who worked on the Michigan State study.
More recently, two papers published in Science in 2011 mixed and matched a handful of beneficial mutations in different types of bacteria. When the researchers engineered those mutations into different strains of bacteria, they found that the fitter strains enjoyed a smaller benefit. Desai’s study examined a much broader combination of possible mutations, showing that the rule is much more general.
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美國民眾對演化論的看法分岐 - K. W. Giberson
What’s Driving America’s Evolution Divide?
Despite the existence of nuanced religious positions on evolution, polls show Americans -- including many former believers -- have come to believe there’s an unbridgeable gulf between faith and science.
Gallop’s latest poll on evolution, taken in May, shows younger Americans rejecting creationism and embracing the idea that evolution is a purely naturalistic process -- bad news for evangelical Christianity. The poll has asked the same questions since 1982, providing a provocative look at where America has been and may be heading.
Every two years, respondents have been asked: “[W]hich of the following statements comes closest to your views on the origin and development of human beings?” The three responses are:
-- “Human beings have developed over millions of years from less advanced forms of life, but God guided this process.”
-- “Human beings have developed over millions of years from less advanced forms of life, but God had no part in this process.”
-- “God created human beings pretty much in their present form at one time within the last 10,000 years or so.”
The numbers fluctuate, of course, but some trends can be discerned. The latest poll shows a significant jump from 15 to 19 percent of the population who believe that God plays no role in human origins. This coincides with -- and is certainly related to -- other polls showing that the “nones” (those with no religious affiliation) are the fastest growing “religion” in the United States. Growth of the nones is a hot topic among American evangelicals. It is their pews that are emptying out and their positions on things like gay marriage, abortion, the role of women, and evolution that are being blamed for young people abandoning their churches. Thirty percent of college students now identify as nones. This coincides with greater acceptance of evolution among the younger demographic.
The “God plays no role” category is the only one on the Gallup poll with a consistent trajectory, rising steadily from nine percent in 1982 and reaching 19 percent this year, with only two one-percent regressions along the way. In contrast, the creationist position -- God created humans 10,000 years ago -- has held steady around 44 percent, with only minor fluctuations.
The God-guided-human-evolution category came in at its lowest point ever, however, which is the most curious feature of the new poll. Two consecutive declines have taken it from 38 percent in 2010 -- where it has hovered for decades -- to 31 percent today.
The trajectories of these numbers are suggestive and correlate with other things we know. For example, young people who abandon organized religion often blame the “anti-science” culture of their church for their disenchantment. Religiosity, naturally, is highly correlated with rejection of evolution, so we should expect to see the “God plays no role” demographic increase unless something reverses the exodus of young people from the church. This seems unlikely, however, as the more significant issue of gay marriage has created an unbridgeable gap between most religious traditions and their young people. I talk to college students for a living, and somewhere near 100 percent of them reject their church’s position on gay marriage. And that number that is steadily hardening.
What is of greater interest to me, however, is the failure of the “middle ground” to capture more support. Believing that God guides evolution in some unspecified way is a “have-your-cake-and-eat-it-too” position, and I would have expected movement into this category. You can accept the science you learned in high school and simply affirm that, in some undefined sense, evolution is “God’s way of creating.” This is known as theistic evolution or evolutionary creation and has been championed vigorously by people like Francis Collins, Ken Miller (although he rejects the label) Sir John Polkinghorne, myself, and others. The BioLogos organization that Collins and I launched a few years ago, and the more recently formed Colossian Forum promote this view. And it is also the view that has been consistently -- if quietly -- promoted at most of America’s evangelical colleges for decades. So why is it moving backwards rather than forwards?
This is an important question for the future of both American science and American Christianity. It matters to science because religiously generated suspicion of established science by well-funded right-wing groups like Answers in Genesis and the Discovery Institute undermines our ability to deal with practical problems, like climate change and vaccinations, as well as educate the next generation of scientists. (And this is in addition to the science denialism on the left. It also matters to religion because young American Christians, by the thousands, are rejecting a religion that tells them to reject science. Many respondents to the Gallup survey apparently perceive the choice to be between evolution and God, rather than between evolution-without-God and evolution-with-God.
My flag has been planted in this failing middle ground since before Gallup started asking people to choose sides. But, over those several decades I have been disappointed in how little progress we have made in articulating what it means to say that “God Guides Evolution.” When the Intelligent Design movement got started, many of us were hopeful that it might move the conversation forward, but it remains mired in the same anti-evolutionary quicksand that gobbled up its predecessor, scientific creationism. It can do little more than say that God -- or, they would insist, “an unknown intelligence” -- is the explanation for this or that evolutionary puzzle.
Evolutionary creation/theistic evolution doesn’t fare much better, however. We can’t explain the difference between our position -- “God guides evolution” -- and that of the atheists -- “evolution runs by itself.” Even such a basic question as the historicity of Adam and Eve is so divisive among evolutionary creationists that many propose a roster of mutually exclusive possibilities rather than address the question directly.
The latest poll suggests that the most robust positions on human origins in America are at the extremes, with an uneasy middle ground. In origins, as in Washington politics, moderates are slowly going extinct.
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生物演化大爆炸的可能因素 - T. Ghose
Evolutionary 'Big Bang' Was Triggered by Multiple Events
Tia Ghose, LifeScience Staff Writer, 09/19/13
The Cambrian explosion, the evolutionary "big bang" that led to the emergence of a trove of complex life forms, was caused by multiple events, researchers argue.
Genetic changes allowing for complex body plans combined with rising sea levels and an influx of chemicals into the ocean probably created the unique conditions needed to set off the Cambrian explosion, researchers argue in a perspectives paper published today (Sept. 19) in the journal Science.
"There was this cascade of events," said study co-author Paul Smith, a paleobiologist at the University of Oxford's Museum of Natural History. "You can see how one process might feed into one another and possibly amplify it as it feeds back."
Evolutionary big bang
About 530 million years ago during the Cambrian Period, the diversity of life on Earth exploded. The first sea-faring predators and prey emerged, animals developed strange and diverse body plans and evolved hard exoskeletons. A recent study revealed that life evolved during the Cambrian Period at a rate about five times faster than today. [Cambrian Creatures: Images of Primitive Sea Life]
Scientists have proposed everything from genetic changes to a starburst in the Milky Way to explain the explosion in diversity.
"There are well over 30 hypotheses out there for the Cambrian explosion," Smith told LiveScience.
Smith and his colleagues looked through all the existing research to see what could explain the evolution of complexity from relatively simple life forms that existed prior to the Cambrian explosion.
"Prior to this, a typical ecosystem would have been a microbial mat with a few things sitting on top," Smith said.
At that time, animals couldn't eat large particles of food, and there were no food webs with predators chasing prey.
The researchers found genetic changes were needed to get the ball rolling toward an explosion of life. By estimating mutation rates, biologists have concluded the genes that code for complex, easily adaptable, bilateral body plans — a necessary precursor for diverse life forms — likely evolved 150 million years prior to the Cambrian Period. (Some evidence suggests this evolution may have occurred closer in time to the Cambrian explosion.)
But genetic changes alone couldn't explain the explosion in diversity.
The rise of sea levels and the flooding of flat, shallow areas of the continents may have served as triggering events. The flooded areas would have provided vastly more habitat for organisms, and the contact between the eroded rock surface and the seawater would have infused minerals, such as calcium and strontium, into the oceans.
Those minerals are toxic to cells, so animals would've needed a way to excrete them.
The animals then would have evolved the ability to incorporate those minerals into their exoskeletons, enabling much more complicated body plans, predation and more modern food webs.
The idea that many factors led to the Cambrian explosion is pretty widespread, said Robert Gaines, a geologist at Pomona College in California, who was not involved in the study.
"I think there are very few people who wouldn't wholeheartedly agree with that," Gaines told LiveScience.
Though the Cambrian explosion is described as a big bang, it was a rather drawn-out affair occurring over 20 million years, Michael Lee, a researcher at the South Australian Museum at the University of Adelaide, who was not involved in the study, wrote in an email.
"One would expect that a range of complex ecological and abiotic drivers might have acted at different times throughout the period," Lee said.
Follow Tia Ghose on Twitterand Google+. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.
Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
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人類演化過程殘留下來的器官 – D. Curnoe
Will We Ever Drop Evolution's Baggage?
Darren Curnoe, 06/27/13
Wisdom teeth, the palmaris longis tendon, ear wiggling: these qualities were desirable millions of years ago but, due to changes in our diet and environment, are slowly disappearing. However, such features aren’t just useless remnants; they provide valuable insights into our evolutionary past.
One of Charles Darwin’s most enduring intellectual legacies was the idea of “common descent” – that the history of life is like a tree with different evolutionary lines sprouting from a common trunk.
Put another way, he recognised that all of life was traceable to a single common ancestor, with evolutionary history unfolding through the inheritance of common features, modified through time as organisms evolved in response to changes in their environment.
As we pass back in time, we humans, as a species, must have shared thousands of common ancestors with other organisms over the past three billion years or more of the history of life, none of which we will ever firmly identify.
It begins for us with the Neandertals (our closest extinct cousin), onto chimpanzees (our closet living relatives) and ultimately back through the tree of life of primates, early mammals and even earlier animals back to the very earliest life when we shared a common ancestor with all living things.
For 150 years or so, biologists have studied the human body for the "hangovers" of our evolution in the form of apparently redundant features dubbed “vestigial” organs.
This evolutionary “excess baggage” has often been thought to reflect common descent and sometimes even stages of evolution. While our views of vestigial features have changed in that time, they are still informative about both our past and the genetic makeup of our species.
Since Darwin’s time, students of natural history have been fascinated by the presence of apparently non-functioning (vestigial) human body structures as evidence for our evolution.
Dubbing them vestigial assumes of course an absence of function, or perhaps disuse. Rather, this turns out to have been wrong in almost all cases, reflecting our ignorance as scientists rather than evolution’s inertia.
When it comes to the fossil record – where function is so much harder to determine – the debate is normally over whether ancient features truly reflect the lifestyle of an organism or whether they might simply be evolutionary excess baggage.
This is an important issue in human evolutionary science. For example, the skeletons of many Australopithecines (such as “Lucy”) possess a mix of features associated with both ape-like tree climbing and human-like terrestrial (bipedal) locomotion.
An important and difficult question to answer in Lucy’s case is: Do the tree climbing features in her skeleton reflect evolutionary hangovers – inherited primitive features that are not functionally important – or are they indicators of a life partially lived in the trees? In all honesty, we’re really not sure.
In his book The Descent of Man, first published in 1871, Darwin listed a large number of human “parts in a rudimentary condition”, being body structures that are either “absolutely useless” or “they are of such slight service” owing to the fact that the conditions under which they evolved no longer exist.
Some interesting examples are:
Smell or olfaction: While humans, being primates, rely heavily on vision, our sense of smell is actually quite well developed with more than 300 genes associated with this special sense. The human nose is even able to detect concentrations as low as a few parts per trillion for some odorous compounds.
Our sense of smell is clearly and intimately linked to our sense of taste, with perhaps 80-90% of taste attributable to smell. It plays a role in our social interactions, including our choice of mates, and helps keep us safe by alerting us to hazards in the environment.
Body hair: Our near nakedness remains one of the greatest mysteries of human evolution. One suggestion is that it may have been associated with endurance running in our evolution 2-3 million years ago owing to the increased convection rates associated with hair loss. This leaves open the question of why have body hair at all?
The meagre hair we have probably performs one or more functions. Suggestions mostly centre on a role in sexual signalling and mate choice owing to the large increases in hair growth associated with sexual maturity from puberty onwards.
Moreover, apocrine sweat glands, located in regions of the body that grow hairs with sexual maturity (such as armpits and groin), produce fluids from puberty onwards that contain pheromones, chemicals designed to illicit a change in the physiology or behaviour of another person.
Wisdom teeth: Primates almost universally possess three molars on each side of their jaw, in both the top and bottom dental rows. Living humans are unusual in that one or more third molar – what we call wisdom teeth – quite commonly doesn’t erupt or fails to develop.
There is a wide range of causes for this phenomenon, including small jaws and dental crowding, but congenital factors seem to be most prevalent. While absence does occur in other primates, it seems to be much more common in humans, with population estimates frequently around 20% (versus less than 5% in other primates). Missing third molars have also been documented in low incidence in other hominins such as Homo erectus.
Reduction in third molar number may indeed be an example of a recent human evolutionary trend and seems to distinguish us from other primate species. Whether it qualifies as vestigial is a matter of perspective, but without doubt the modern agricultural/industrial diet places few demands on our teeth and combined with modern dentistry we can get away with fewer teeth.
Vermiform appendix: The human appendix was for a long time thought to be the quintessential vestigial organ. It is now known to play a role in the immune system, contains lymphatic vessels that help regulate pathogens and assists with the management of digestive system movement and removal of body waste.
Coccyx: While our tailbones don’t bear any direct body weight when we’re upright, unlike the remaining spine and pelvis, they do play a vital role in the human body. Importantly, they provide attachment for muscles that support the pelvic organs, such as the pelvic sling muscle the pubococcygeus, as well as the major locomotor muscle, the gluteus maximus (the largest of the “glutes”).
Prostate gland: The function of this male organ, one of the accessory sexual glands, is now well understood – unlike in Darwin’s day. It makes a fundamental contribution to semen, both in the form of supporting reproduction and aiding sperm survival, and also contains antimicrobial components that may help protect against urethral infections.
Vomeronasal organ: Many mammals possess a pair of organs on either side of the nasal septum on the floor of the nasal cavity used for the detection of pheromones. Until recently, they were thought to be absent from humans, but they have now been shown to be present in most people.
While understanding of their precise function and effects remains controversial, it seems likely that, as with other mammals, their role is at least in part to detect pheromones from other people and to help regulate aspects of reproductive physiology and behaviour.
In other words, they seem to detect the pheromones produced by the apocrine sweat glands of other people that influence our decisions about mate choice and the sexual partners we select.
A True Vestigial Structure?
When humans walk, one foot bears the body weight while the opposite one pushes off to propel the body. The pushing off foot is normally rigid – kept so by ligaments and muscular tendons – in order to act as an efficient lever.
In other primates this foot is much more mobile and actively alters position to accommodate uneven surfaces. One way this occurs is through the “mid-tarsal break” or a bending of the mid-foot.
The mid-tarsal break is thought to have been lost in humans as an adaptation to our bipedal locomotion. Indeed, it seems to be lacking in most species of Australopithecus, including Lucy’s kind, but may be present in Australopithecus sediba.
A recent study published in the American Journal of Physical Anthropology shows in a sample of 398 adult subjects studied, almost 10% of them actually possess the primate mid-tarsal break.
This runs counter to orthodoxy and is not easily explained. While the feature is associated with people with flatter arches and a tendency to roll the foot inwards when walking, the bending is counteracted with shoes, so has little apparent real impact on movement.
The mid-tarsal break, more than any other feature studied over the past 150 years of evolutionary biology, probably justifies the appellation “vestigial.” It seems to be about as compelling an example of evolutionary excess baggage as one can imagine.
Yet, further research may show even in this case that evolution has co-opted the structure for two-footed working in a way that was unexpected. It may even prove to be advantageous rather than simple inertia.
At a minimum, it powerfully shows our common descent with other apes, with whom we share the vast majority of our DNA and so many of our physical and behavioural features. We are, after all, just a “jumped-up” ape!
Darren Curnoe is an anthropologist, evolutionary biologist and archaeologist at University of New South Wales.
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演化論新聞中5個討厭的詞彙 - O. Knevitt
The Top 5 Most Irritating Terms In Evolution Reporting
Oliver Knevitt, 04/17/13
Evolution is misunderstood by millions. And, it has to be said, a lot of the time, this problem isn't helped by the way things are reported on the TV or in the news.
These are the 5 most common terms that, when I hear them used, I die a little. Though their effect is subtle, all of these terms perpetrate common myths about the way evolution works. The sooner they become extinct, the better!
1. Survival of the Fittest
Now, this term is something that often gets used synonymously with natural selection. In fact, it wasn't actually coined by Darwin himself; it was first used by Herbert Spencer, though Darwin later came to use it extensively.
The problem with the phrase "survival of the fittest", in my view, is that it rather misrepresents the way that selection really works. This is because it isn't really the survival of the fittest organism that drives evolution. It's the death of the least fit organism.
I can see how "survival of the fittest" appealed to victorian sensibilities! Instead of implying a brutal, red-in-tooth-and-claw vision of nature, it implies a striving towards self improvement. Which is, it has to be said, appealing. Unfortunately, it's neither borne out by theory nor facts.
2. Living fossil
This is another very appealing term. Below was the best example I could find after a quick rifle through the drawers here in Leicester. It is a maple leaf next to a modernish mapleish leaf (sycamore). [For some much better examples, check out the Living Fossils website.] UPDATE - don't do that, it's a creationist website, as someone has kindly pointed out by email. Does anyone know of a website that showcases living fossils without an agenda??
It's so appealing because for some so called living fossils really look like just that: like a sorcerer has breathed life into an inanimate fossil. Or that the fossil animal has been there all along, biding its time.
However, it just doesn't reflect reality. No organism can survive without adapting. Yes, it may well be that their body form seems relatively conservative, but then, it is likely there is a lot of change that we may have missed.
I think it's very improbable that the same environment would be around for hundreds of millions of years, and even more improbable that the same organism would be able to stay on top of the game for that long. Instead, these organisms have necessarily had to flexible; ready to adapt to the tumultuous changes in the environment over the aeons.
Richard Fortey advocates the term "survivors" instead; a much more preferable term. These animals are simply very, very successful, and are not some sort of dinosaur.
3. Missing link
This is undoubtedly the worst term in general use. There are many, many fundamental problems with this term, as I've written about before, but one of the main problems is that a link implies a chain; a great chain of being, with the dumber animals at the bottom and clever man at the top.
Yet, there is a much deeper reason why I'd like this term to be dead and buried. It is entirely perjorative. It is only used by those wishing to deinigrate evolution. It automatically implies that we are involved in some sort of gigantic join-the-dots puzzle; that we spend our time desperately poring through rocks trying to find that one elusive crocoduck that will fill in our tree and finally legitimize our ill-conceived agenda.
The reality is that, if anything, it's the other way round. We have far too many fossils and which ones are closer to the ancestral line and which are further is the tricky bit.
This is the one term that I am willing to issue a full, North Korea style, gagging order on. The main reason is that media reporting is obsessed with this idea. What we're interested in is uncovering the history of life on Earth and understanding how evolution works. We're not simply trying to prove that it happened.
In summary, we are not missing anything, and we're not looking, thank you very much.
4. More evolved/less evolved
I have to say that, in outreach work that I've done, I've succumbed to saying this. It's just too convenient to say. Instead, however, I prefer the term basal. A lamprey is considered to be a more basal vertebrate than a human because it shares similar characteristics with what we expect the common ancestor of all vertebrates to have. We didn't evolve from a lamprey; we share a common ancestor that is just as distant from lampreys as it is from humans, it only looks a lot more like a lamprey.
Strictly speaking, we are no more evolved than a lamprey. We are good at we do and lampreys are good at what they do.
Now, I'm sure that a lot of people will call me a pedant for disliking this term. The problem with using the word adaptation instead of trait or character is that it assumes that it got there via adaptionism.
It's undeniably true that most important force that shapes the morphology of an organism is adaptation, i.e. evolving them so that they are better adapted to the task required. However, it is not the only force that shapes body parts or behaviours. Often, they are there because of constraints on evolution; they may arise simply in tandem with the evolution of another body part. So, I don't like it because it makes us inadvertently make assumptions about the origin of any character of an animal.
Really, the people that ruined this term were evolutionary psycholgists, who, it's fair to say, regularly take an overwhelmingly adaptionist view of the human body. The worst example I can think of is the hypothesis that women like pink because it is an adaptation to picking berries. By using the term adaption, it automatically implies that there must be a selective reason for this. Remember what I was saying about survival of the fittest? This is a perfect example of that being misapplied. It is not simply that those who preferred pink were more likely to survive to have offspring; it would necessarily mean that those who didn't prefer pink would have to die. Which is... improbable, to say the least.
There you have it. Now, I realize that there are probably less serious problems than this in media reporting. The problem is that, the more these terms wash over us by being slipped into the odd news report here and there, we're more and more anaesthetised to their erroneous connotations. If we replaced this with more correct language, we wouldn't have the widespread misunderstanding of evolution that there is currently. Or at least, not as bad.
It's not particularly a problem for us paleontologists and evolutionary biologists, because we use specialist terminology. For instance, I might describe something as stem group if it's part of a transitional sequence; a term which has a precise definition, meaning we can be accurate and concise when we describe ideas to one another.
Obviously, journalists can't provide a glossary with every article; it belies the entire point of journalism, namely being to digest a complex story and condense it down to one nice, shiny nugget of information. But there has to be better ways of reporting stories, rather than using these loaded terms.
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當代「綜合演化論」的發展 - M. Pigliucci
The Evolutionary 16: Shaping a New Evolutionary Synthesis While Keeping the Looneys at Bay
Massimo Pigliucci, Skeptic (Altadena, CA)
EVERY MATURE FIELD OF SCIENCE IS characterized by an established conceptual framework -- what philosopher of science Thomas Kuhn called a "paradigm." Every now and then, according to Kuhn, scientists encounter a series of problems that cannot be resolved within the current paradigm. If this situation persists, a crisis eventually ensues, which is resolved by abandoning the reigning paradigm and embracing a new one.
The history of science, however, teaches us that things are not always that tidy. Biology, for instance, arguably has never undergone a paradigm shift since Darwin, although the Darwinian revolution does count as an entirely new paradigm when compared to William Paley's intelligent design-based explanations for the diversity of life. Rather, the original "Darwinism" of the mid-19th century with its twin concepts of common descent and natural selection was improved by the so-called neo-Darwinism of the late 19th century which eliminated any remaining vestiges of Lamarckism -- the idea that environmentally-induced characters can be inherited. The first decades of the 20th century saw another marked expansion of evolutionary theory, which came to be known as the "Modern Synthesis' -- a complex theoretical structure that reconciled the basic Darwinian ideas with the then new fields of Mendelian and statistical genetics.
The Modern Synthesis was arguably completed during the 1940s, with the publication of a series of seminal volumes by some of the preeminent evolutionary biologists of the time, including Theodosius Dobzhansky, Ernst Mayr, and George Gaylord Simpson. To this date, graduate level textbooks are built around the same conceptual structures laid out by the Modern Synthesis, although of course much has happened in biology since: the molecular revolution, the rebirth of the study of the evolution of development ("evo-devo") and the genomic era, to name a few. The question has therefore been posed by several people over the past decade or so: do we need an Extended Evolutionary Synthesis? Stephen Jay Gould among others thought so, and he tried to articulate one in his last technical book, The Structure of Evolutionary Theory.
To further explore the nature of a possible Extended Evolutionary Synthesis, Gerd Muller and I recently hosted a workshop on the current status of evolutionary theory at the Konrad Lorenz Institute for Evolution and Cognition Research, in Altenberg near Vienna, Austria. We invited 16 people who have been active in discussions of this kind and asked them to talk about where they think evolutionary biology is going. The so-called "Altenberg 16" are: John Beatty (University of British Columbia), Wemer Callebaut (University of Hasselt), Sergey Gavrilets (University of Tennessee), Eva Jablonka (Tel Aviv University), David Jablonski (University of Chicago), Marc Kirschner (Harvard University), Alan Love (University of Minnesota), Gerd Muller (University of Vienna), Stuart Newman (New York Medical College), John Odling-Smee (Oxford University), Massimo Pigliucci (Stony Brook University), Michael Purugganan (New York University), Eors Szathmary (Collegium Budapest), Gunter Wagner (Yale University), David Sloan Wilson (Binghamton University), and Greg Wray (Duke University).
In order to appreciate what we did in Altenberg, however, one first needs to understand the Modern Synthesis. At the beginning of the 20th century, standard Darwinian theory was in a bit of a crisis because it seemed incompatible with the rediscovery of Mendelian genetics, which in turn seemed hard to reconcile with statistical genetics (what today is called quantitative genetics). The new Mendelian genetics seemed to show that traits are controlled by discrete units (the genes) which would produce only discrete phenotypes. This was contrary to the requirement of continuous variation on which Darwin had built his gradualistic theory, as well as to the work being carried out by statistical geneticists (termed biometricians), who were interested in characters that display the typical bell curve, or continuous distribution. The resolution to this impasse emerged gradually, thanks to the work of Ronald Fisher, Sewall Wright, J.B.S. Haldane and the already mentioned additional architects of the Modern Synthesis. Essentially, population genetics theory as we know it today was born, and it elegantly showed the compatibility of Mendelian genetics, statistical genetics, and neo-Darwinism: some characters are influenced principally by few genes, and they follow Mendelian roles, but many others are influenced by tens or hundreds of genes, whose separate effects produce a cumulatively smooth, bell-shaped distribution. Both Mendelian and quantitative characters are then subject to natural selection, as Darwin maintained.
The Modern Synthesis itself, however, was clearly born incomplete, as all scientific theories are, to some extent. For instance, the extrapolation of population genetic processes to the long time periods that are the province of paleontology was assumed with little additional discussion. The entire body of knowledge in embryology and developmental biology was set aside because it had not been developed within an evolutionary framework. And even ecology was simply assumed to be part of the picture, as opposed to being organically integrated in a coherent conceptual framework. Moreover, in the almost 70 years since the Modern Synthesis, biologists have uncovered the structure of DNA, found that there are types of inheritance that are not directly tied to the genes (so called epigenetic effects), started a whole new field of evolutionary developmental biology, and discovered molecular mechanisms that are capable of unleashing a wide array of phenotypic changes under stressful conditions ("capacitors" of phenotypic evolution), affecting what has come to be known as the "evolvability" of populations and species. Paleontologists such as Gould and Niles Eldredge have shown that the fossil record has much to teach us about the tempo and mode of evolution, and theoretical models have indicated that the Modern Synthesis' relatively simple conception of population genetic phenomena barely scratches the surface of the reality of biological dynamics. More controversially, complexity theory has for the first time since the Darwin-Paley dispute offered us the possibility of additional mechanisms, besides natural selection, that can generate order and complexity.
None of the above should be misconstrued as a rejection of the Modern Synthesis, or of neo-Darwinism, or even of the original Darwinism insight. On the other hand, one can easily see why there has been much excitement and discussion in the field over the past decade or so: so many new empirical discoveries, and so much conceptual advancement in a variety of areas of theoretical biology are bound to raise the question of whether a theoretical structure put in place seven decades ago is still entirely adequate to the task. Hence the workshop at Altenberg and the forthcoming edited book that MIT Press is going to publish in 2009 with each author contributing a chapter covering a wide range of topics, including: "Chance, History, and Natural Selection," "The Epigenetic Turn: The Challenge of Soft Inheritance," "Phenotypic Plasticity as Causal Factor in Evolution," "Modularity, Evolvability, and the Evolution of Genetic Architecture," "The Structure of Evolutionary Theory and Biological Knowledge."
Predictably, not everybody agrees that there is any need of an Extended Evolutionary Synthesis. Some of my colleagues have been commenting, in print or at meetings, that all the new stuff is perfectly compatible with the current paradigm, or that there isn't really much radically new, especially conceptually, and therefore there is no reason to call for special meetings or discussions. I must respectfully disagree with the "conservatives" in this case.
First, there is a difference between compatibility and implication: few people (including myself) argue that the new discoveries and theoretical advancements are incompatible with the Modern Synthesis. However, it seems to me much harder to argue that the new material was "implied" by the Modern Synthesis and that therefore there really isn't much radically new to talk about.
Second, it is easy to show -- as a matter of historical record -- that ideas like evolvability, capacitance, epigenetics in the modern sense, phenotypic plasticity, or emergent complexity were simply nonexisting in the biological literature at the time of the Modern Synthesis. If these terms have distinct meanings as opposed to being simple reformulations of older ideas -- and they do -- then there is much novelty out there that biologists need to deal with.
Of course, the proof in science is always in the pudding: only time will tell whether we are moving toward a true and significant expansion of the basic conceptual framework of evolutionary biology, or we are simply tweaking some of the peripheral branches of the same structure that Darwin and the modern synthesists put in place. While we are waiting for the long-term outcome, we have to deal with the usual nonsense on the part of creationists, intelligent design proponents and the like. In this case, the opening shot was published by an independent journalist, Suzan Mazur, who wrote a piece in the New Zealand-based online outlet Scoop entitled "Altenberg! The Woodstock of Evolution?" in which she characterized the workshop as "a gathering of 16 biologists and philosophers of rock star stature." The hype, rather embarrassing to begin with, reached a crescendo as the article progressed, when Mazur stated that "despite the fact that organizers are downplaying the Altenberg meeting as a discussion about whether there should be a new theory, it already appears a done deal.... Indeed, history may one day view today's 'Altenberg 16' as 19th century England's 'X Club' of 9 -- Thomas Huxley, Herbert Spencer, John Tyndall, et al. -- who so shaped the science of their day." Okay, few people would mind being compared to a rock star (though, alas, without the corresponding income), and any scientist would certainly enjoy being referred to as a modern day Thomas Huxley (the famous "Darwin's bulldog" of the Victorian age), but Mazur's presentation of the scope of the workshop was misleading at best.
Mazur's long article turned out to be a hopelessly confused hodgepodge of actual science, badly misunderstood science, philosophy good and bad, and crackpotism. For instance, one of the characters introduced by Mazur to the public was Stuart Pivar, an art collector who had been sending more or less threatening emails to me, my graduate students, and several of my colleagues because we were not taking seriously his "theory" about the evolution of development. (Pivar's "theory" is based on the idea that all life forms are variants of one basic form, a concept that arches back to pre-Darwinian times -- -and his "proof' is that he can build plastic models that can be reshaped as one wishes by twisting and turning them.) Mazur presented Pivar as a scientist who "is not dependent on government grants to carry out his work" (true, except that he is not a scientist, and I seriously doubt he would be able to get government grants if he applied), and one who "has paid the price for [his unorthodox theory] on the blogosphere." In other words, Mazur painted us as rock star celebrity-rebels, and Pivar as a misunderstood genius who is shunned by the scientific community because of a secret natural selection cabal. Needless to say, both portraits are as far from the truth as an episode of the X-Files.
This may have been nothing more than an amusing incident and one more reminder of what can happen when one talks to journalists without double-checking their credentials. But we live in the era of the Internet, and the matter was far from being over. The very same day, Paul Nelson, a contributor to "Uncommon Descent" -- the official blog of the pro-intelligent design Discovery Institute -- picked up on the Scoop article, declaring it worthy of attention on the grounds that "evolutionary theory is in -- and has been, for a long time -- a period of great upheaval. Much of this upheaval is masked by the noise and smoke of the ID debate, and by the steady public rhetoric of major science organizations, concerned to tamp down ID-connected dissent." Oh boy. To my further surprise, not only was Nelson's short commentary picked up by a variety of pro- and anti-evolution blogs, but eventually the Mazur article came to the attention of serious media outlets, including the New York Times, Science and Nature. Science published a detailed article the same week the workshop was being held, beginning with a whole paragraph devoted to Mazur's "coverage." At least the Science reporter wryly pointed out that I am no Jimi Hendrix, shifting immediately to a more realistic portrayal of what we actually did in Austria that summer.
But Mazur herself wasn't through. She began publishing on Scoop a six-part "investigative" story entitled "The Altenberg 16: Will the Real Theory of Evolution Please Stand Up?" Once again, this turned out to be a longwinded ramble that displayed in full color Mazur's lack of understanding of the subject matter and penchant for conspiracy theorizing. What was both illuminating and amusing was the shifting portrayal of yours truly that she presented to her readers. In the first article I was introduced as that "rare combination -- a consummate scientist with a sense of humor," and she made a charming reference to the fact that I had a birthday present in my hands for my daughter. But subsequently I made the mistake of making dear, politely I thought, that I was not too pleased with the distortions that Mazur was responsible for. This turned me into a rather shady character in her later articles. "Massimo Pigliucci is a man on the move," she wrote, "but who is he? And why was he born in Liberia during the regime of William Tubman?" (because my father was there working for a British company that built roads, she could have found out, had she asked). From consummate scientist I had become "flamboyant" (something she clearly didn't mean as a compliment) and observations on my sense of humor had given way to remarks on my receding hair line (a sad but true fact of life in my '40s).
What one should not take home from this story is what many of my colleagues have too quickly concluded: that one should not talk to reporters. Scientists have an ethical duty to the public to explain what they do and why. This is because what scientists do may indeed affect the public welfare, and even when it doesn't, it is probably funded, directly or indirectly, by tax payers' money. Moreover, it simply does not help the image of science if scientists keep propagating the stereotype of the white coat aloof in the ivory tower. But by the same token, journalists also have a duty to do their homework and to present stories in an interesting, but not unduly sensationalist, fashion. We are all after the Nobel or the Pulitzer, at least in our dreams, but few of us have even a fighting chance to get there. In the meantime, we ought to do our job, science or journalism, with the degree of seriousness that is rightly expected from professionals, not to mention quite simply from the fact that we are grownups.
The web site of the Konrad Lorenz Institute devoted to the Altenberg meeting:
The original Mazur article on "the Woodstock of Evolution":
The beginning of Mazur's six-part "expose" of evolutionary theory:
My own final entry on the Rationally Speaking blog about the Altenberg events:
A Panda's Thumb blog entry on the creationist nonsense surrounding the Altenberg workshop:
A Pharyngula blog entry commenting on the Altenberg meeting and some of the hype generated by creationists: http://scienceblogs.com/pharyngula/2008/07/altenberg_2008_is_over.pbp
Carroll, R. L. 2000. "Towards a New Evolutionary Synthesis." Trends in Ecology and Evolution 15: 27-32.
Dobzhansky, T. 1937. Genetics and the Origin of Specks. New York, Columbia University Press.
Fisher, R. A. 1930. The Genetical Theory of Natural Selection. Oxford, Clarendon.
Gould, S.J. 2002. The Structure of Evolutionary Theory. Cambridge, MA, Harvard University Press.
Haldane, J. B. S. 1932. "The Time of Action of Genes, and its Bearing on Some Evolutionary Problems." The American Naturalist 66: 5-24.
Kuhn, T. 1970. The Structure of Scientific Revolutions. Chicago, University of Chicago Press.
Love, A. C. 2006. "Evolutionary Morphology and Evo-Devo: Hierarchy and Novelty." Theory in Biosciences 124: 317-333.
Mayr, E. 1942. Systematics and the Origin of Species. New York, Dover.
Mayr, E. and W. B. Provine 1980. The Evolutionary Symbols. Perspectives on the Unification of Biology. Cambridge, MA, Harvard University Press.
Muller, G. B. 2007. "Evo-Devo: Extending the Evolutionary Synthesis." Nature Reviews Genetics Advanced Online Publication, November: 1-7.
Newman, S. A. 2005. "The pre-Mendelian, Pre-Darwinian World: Shifting Relations Between Genetic and Epigenetic Mechanisms in Early Multi-cellular Evolution." Journal of Bioscience 30: 75-85.
Pennisi, E. 2008. "Modernizing the Modern Synthesis." Science 321: 196-197.
Pigliucci, M. 2007. "Do We Need an Extended Evolutionary Synthesis?" Evolution 6112: 2743-2749.
Pigliucci, M. and J. Kaplan 2006. Making Sense of Evolution: The Conceptual Foundations of Evolutionary Biology. Chicago, IL, Chicago University Press.
Robert, J. S. 2004. Embryology, Epigenesis, and Evolution: Taking Development Seriously. Cambridge, England, Cambridge University Press.
Simpson, G. G. 1944. Tempo and Mode in Evolution. New York, NY, Columbia University Press.
Sultan, S. E. 2007. "Development in Context: The Timely Emergence of Evo-Devo." Trends in Ecology and Evolution 2211: 575-582.
Wagner, G. P. 2007. "The Developmental Genetics of Homology." Nature Genetics 8: 473-479.
Wright, S. 1932. "The Roles of Mutation, Inbreeding, Crossbreeding and Selection in Evolution." Proceedings of the Sixth International Congress of Genetics: 356-366.
Publication information: Article title: The Evolutionary 16: Shaping a New Evolutionary Synthesis While Keeping the Looneys at Bay. Contributors: Pigliucci, Massimo - Author. Magazine title: Skeptic (Altadena, CA). Volume: 14. Issue: 3 Publication date: September 22, 2008. Page number: 10+. © 2009 Skeptics Society & Skeptic Magazine. COPYRIGHT 2008 Gale Group.
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影響大腦演化的基因突變 - ScienceDaily
Tiny Genetic Variations Led to Big Changes in the Evolving Human Brain
ScienceDaily (May 30, 2012) -- Changes to just three genetic letters among billions contributed to the evolution and development of the mammalian motor sensory circuits and laid the groundwork for the defining characteristics of the human brain, Yale University researchers report.
In a study published in the May 31 issue of the journal Nature, Yale researchers found that a small, simple change in the mammalian genome was critical to the evolution of the corticospinal neural circuits. This circuitry directly connects the cerebral cortex, the conscious part of the human brain, with the brainstem and the spinal cord to make possible the fine, skilled movements necessary for functions such as tool use and speech. The evolutionary mechanisms that drive the formation of the corticospinal circuit, which is a mammalian-specific advance, had remained largely mysterious.
"What we found is a small genetic element that is part of the gene regulatory network directing neurons in the cerebral cortex to form the motor sensory circuits," said Nenad Sestan, professor of neurobiology, researcher for the Kavli Institute for Neuroscience, and senior author of the paper.
Most mammalian genomes contain approximately 22,000 protein-encoding genes. The critical drivers of evolution and development, however, are thought to reside in the non-coding portions of the genome that regulate when and where genes are active. These so-called cis-regulatory elements control the activation of genes that carry out the formation of basic body plans in all organisms.
Sungbo Shim, the first author, and other members of Sestan's lab identified one such regulatory DNA region they named E4, which specifically drives the development of the corticospinal system by controlling the dynamic activity of a gene called Fezf2 -- which, in turn, directs the formation of the corticospinal circuits. E4 is conserved in all mammals but divergent in other craniates, suggesting that it is important to both the emergence and survival of mammalian species. The species differences within E4 are tiny, but crucially drive the regulation of E4 activity by a group of regulatory proteins, or transcription factors, that include SOX4, SOX11, and SOX5. In cooperation, they control the dynamic activation and repression of E4 to shape the development of the corticospinal circuits in the developing embryo.
Other Yale-affiliated authors of the paper are Kenneth Y. Kwan and Mingfeng Li.
Primary funding for the research came from the National Institutes of Health and March of Dimes.
The above story is reprinted from materials provided by Yale University. The original article was written by Bill Hathaway.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
1. Sungbo Shim, Kenneth Y. Kwan, Mingfeng Li, Veronique Lefebvre, Nenad Šestan. Cis-regulatory control of corticospinal system development and evolution. Nature, 2012; DOI: 10.1038/nature11094
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推薦《演化論入門》 -------- M. White
Michael White, 03/20/09
There is a conversation about evolution that I’m apparently doomed to replay over and over with various family members, friends and acquaintances.
I tell a friend that the evidence for evolution is overwhelming - everywhere in biology you find the signature of evolution; in every little bizzare, unexpected nook of biology you find unmistakeable evidence that all life is related, descended from common ancestors that lived long ago and took forms that were very different from what we observe in today’s organisms. We swim in a deluge of evidence, and I’m baffled that anyone can disregard the pervasive stamp of evolution in nature.
Whoever I’m having this conversation with is equally baffled. How can I look around at the unparalleled complexity of nature, at the amazing adaptations possessed by millions of species, and think that this all came about through an unintelligent process?
To end this mutual bewilderment between biologists and the 45% of the US population that doesn’t accept evolution, we need readable, friendly books that explain why biologists think the way they do. Jerry Coyne steps into the gap with a straightforward introduction to the wide-ranging findings from disparate fields of biology that solidly support the modern theory of evolution.
As the no-nonsense title suggests, Why Evolution is True lays out, in plain language, the basic ideas behind evolution and the types of evidence that support these ideas. Coyne takes a reader on a tour of paleontology, evo-devo, biogeography, natural selection and genetic drift, sexual selection, and his own professional specialty, speciation. He finishes up with a chapter on the one evolutionary branch that most us find more interesting than any other, that is, our own, and with the always obligatory chapter laying to rest the ill-founded but widespread concerns that our children will fall into an uncivilized, Hobbesian state if they’re taught that they descended from monkeys and slime.
Coyne’s book has several distinct advantages over many other books in the pop-evolution genre. For one, he’s conversational, which makes the book an easy read. Learning the basics of evolution, doesn’t have to be hard, and Coyne makes it fun. Coyne may not be a prose stylist like Richard Dawkins or Stephen Gould, but his clear thinking is accompanied by clear writing. Occasionally I thought that Coyne assumed more background knowledge that most readers might have (I wish more people knew what igneous rocks and amino acids are, but most readers probably don’t), however, with an occasional trip to Wikipedia, any literate, interested reader will do fine.
Coyne’s clear style is supported by an effective explanatory strategy. In the first chapter, he lays out some main principles of evolution:
1) evolution is gradual change over often long periods of time, resulting in organisms that can be very different from their ancestors;
2) evolution is gradual - dogs don’t give birth to cats, lizards don’t give birth to chickens; even rapid evolutionary change is gradual by any human understanding of the term;
3) new species often arise by the splitting of genealogical branches, which means that;
4) today’s living species have descended from common ancestors;
5) natural selection acting on variation is responsible for producing organisms that are highly adapted to their environment, and;
6) other processes, like genetic drift, shape evolutionary trajectories.
From general principles like these, Coyne demonstrates that scientists can make predictions about what we expect to find in nature. For example, evolutionary theory suggests that there will be a predictable evolutionary succession of fossils. Whales have certain features that make us suspect that they descended from land-dwelling mammals; so we expect to see a transition from land to sea animals in the fossil record, which we do see. If land-dwelling vertebrates evolved from fish ancestors, we should be able to find fossils of fish-like animals with primitive limbs, which we do find.
In each chapter, Coyne lays out evolutionary predictions, and then uses well-chosen examples to show how those predictions are confirmed.
Coyne then takes the argument one step further. Evolution generates clear expectations of what we should find in nature, while creationism can only explain nature by appealing to arbitrary, inscrutable decisions made by an inaccessible designer. Certainly an omnipotent designer could have chosen to make the world this way, but creationists have no testable explanation for why the designer chose to do it one way, instead of another. Thus, intelligent design advocate Michael Behe ascribes a peacock’s tail to a designer’s whimsy, while biologists say the tail is the result of sexual selection. Behe’s idea is arbitrary; biologists’ claims flow naturally from evolutionary theory. Behe’s idea can’t be tested; biologists have tested theirs.
While underscoring the intellectual bankruptcy of a design explanation, Coyne wisely steers clear of an outright attack on religion, and in fact he hardly spends any time at all refuting specific arguments of creationists. This book is not a take-down of creationism; it’s a primer on evolution intended for a broad audience. Coyne is interested in science, and leaves readers free to draw their own religious conclusions, which is exactly how this issue is also treated in professional science circles. Scientists agree on the science, and differ with each other over religion.
The book finishes up with an interesting discussion of the common worry that teaching evolution to our kids will unleash “the beast within.” (I don’t know about you, but it doesn’t take evolution to unleash the beast within my kids - it pretty much starts out unleashed.) Instead of just rattling off a few bromides about how science doesn’t have to tell us how to act, Coyne takes on some of the ideas of evolutionary psychology and the idea of genetic determinism.
If we’ve evolved a certain way, do we have to be that way? No - just because something’s genetic, doesn’t mean you can’t modify it. The most commonly used example of this idea is eyesight: Coyne’s poor eyesight (and mine) is the result of genetics, yet it’s 100% fixable with an environmental change, a pair of glasses. Some genetic traits are more susceptible to environmental change than others, but the point stands: genes aren’t the same thing as destiny.
We’ve long needed more engaging, readable, non-polemical books that provide a general overview of why biologists think about evolution the way they do. Should I find myself again engaged with a friend who is baffled that I think the evidence for evolution is overwhelming, Why Evolution is True will be the first book I recommend.
Why Evolution is True
by Jerry A. Coyne
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