Why the switch from foraging to farming?

Randolph E. Schmid, AP Science Writer

WASHINGTON – Thousands of years ago, our ancestors gave up foraging for food and took up farming, one of the most important and debated decisions in history.

Was farming more efficient than foraging? Did the easily hunted animals die out? Did the environment change?

A new study by Samuel Bowles of the Santa Fe Institute in New Mexico argues that early farming was not more productive than foraging, but people took it up for social and demographic reasons.

In Monday's edition of Proceedings of the National Academy of Sciences, Bowles analyzed what it would take to farm under primitive conditions. He concluded farming produced only about three-fifths of the food gained from foraging.

But, Bowles notes, farming became the most common way of living between 10,000 and 5,000 years ago because of its contribution to population growth and military power.

Without the need for constant movement, child-rearing would have been easier and safer, leading to a population increase, Bowles said. And since stored grain might be looted, farmer communities could have banded together for defense and would have eventually pushed out neighboring foragers, he suggests.

Brian Fagan, a professor emeritus of archaeology at the University of California, Santa Barbara, called Bowles' ideas "provocative and fascinating."

It had been suspected that the earliest farming was not necessarily more productive, said Fagan, who was not part of the research.

"What he does is to draw attention to the social and demographic factors that contributed so importantly to the spread of farming," Fagan said. "This is a useful contribution to a debate about agricultural origins that has been under way for generations."

Online: http://www.pnas.org

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Humans may have left Africa earlier than thought

Randolph E. Schmid, Ap Science Writer

WASHINGTON – Modern humans may have left Africa thousands of years earlier than previously thought, turning right and heading across the Red Sea into Arabia rather than following the Nile to a northern exit, an international team of researchers says.

Stone tools discovered in the United Arab Emirates indicate the presence of modern humans between 100,000 and 125,000 years ago, the researchers report in Friday's edition of the journal Science.

While science has generally accepted an African origin for humans, anthropologists have long sought to understand the route taken as these populations spread into Asia, the Far East and Europe. Previously, most evidence has suggested humans spread along the Nile River valley and into the Middle East about 60,000 years ago.

"There are not many exits from Africa. You can either exit" through Sinai north of the Red Sea or across the straits at the south end of the Red Sea, explained Hans-Peter Uerpmann of the Center for Scientific Archaeology of Eberhard-Karls University in Tuebingen, Germany.

"Our findings open a second way which, in my opinion, is more plausible for a massive movement than the northern route," he said in a telephone briefing.

Because of the different climate at the time, Arabia was moister and would have been a grassland with plenty of animals for prey, he added.

And the lower sea levels at that time meant that the narrow point at the southern end of the Red Sea would have separated Africa and Arabia by between one-half and 2 1/2 miles, said Adrian G. Parker of Oxford Brookes University in England.

That should not have been a difficult crossing for people used to dealing with east African lakes and rivers where they used rafts or boats, Uerpmann said.

The techniques used to make the hand axes, scrapers and other tools found at Jebel Faya in Sharjah Emirate suggest they were produced by people coming from somewhere else, said Anthony E. Marks of Southern Methodist University in Dallas, adding that there are similar tools made about that time in East Africa.

"If these tools were not made by modern man, who might have made them?," Marks asked. "Could Neanderthals have made them?"

Neanderthals were mainly in Europe and migrated into Russia but "there is no evidence for any Neanderthals south of that" zone at that time, he said. "To suggest one group of Neanderthals took a turn south and went several thousand kilometers ... seems to me a very difficult explanation and one that doesn't follow any reasonable logic."

The tools were dated using optically stimulated luminescence, which is able to date the sand grains on top of the tools and determine when they were last exposed to light, explained Simon J. Armitage of the University of London.

The discovery "points convincingly to an early dispersal of (anatomically modern humans) along a southern route, from eastern Africa into South Arabia," said G. Philip Rightmire of Harvard University, who was not part of the research team.

Rightmire said "it is reasonable to hypothesize that Arabia represents a separate center for population expansion, in addition to the northern Levantine corridor. This hypothesis remains to be tested, as new evidence is compiled."

The research was supported by the government of Sharjah, Heidelberg Academy of Sciences, Humboldt Foundation, Oxford Brookes University and the German Science Foundation.

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Online: http://www.sciencemag.org

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World's oldest human remains claimed in Israel

JERUSALEM (AFP) – Israeli archaeologists have discovered human remains dating from 400,000 years ago, challenging conventional wisdom that Homo sapiens originated in Africa, the leader of excavations in Israel said.

Avi Gopher, of Tel Aviv University's Institute of Archaeology, said testing of stalagmites, stalactites and other material found in a cave east of Tel Aviv indicates that eight teeth uncovered there could be the earliest traces so far of our species.

"Our cave was used for a period of about 250,000 years -- from about 400,000 years ago to about 200,000 years ago," he told AFP.

"The teeth are scattered through the layers of the cave, some in the deeper part, that is to say from 400,000 years and through all kinds of other layers that can be up to 200,000 years. The oldest are 400,000 years old", he added."

That calls into question the widely held view that Africa was the birthplace of modern man, said Gopher, who headed the dig at Qesem Cave.

"It is accepted at the moment that the earliest Homo sapiens that we know is in east Africa and is 200,000 years old, or a little less. We don't know of anywhere else where anyone claims to have an earlier Homo sapiens," he said.

Gopher said the first teeth were discovered in 2006 but he and his team waited until they had several samples, then conducted years of testing, using a variety of dating methods, before publishing their findings.

Digging continues at the cave, the university said, with researchers hoping to "uncover additional finds that will enable them to confirm the findings published up to now and to enhance our understanding of the evolution of mankind, and especially the appearance of modern man."

http://news.yahoo.com/s/afp/20101229/ts_afp/israelafricaarchaeology

Finger Bone Points to New Branch of Humanity

Charles Q. Choi, LiveScience Contributor
A finger bone from Siberia now reveals a previously unknown group of ancient humans once existed there, one neither like us nor Neanderthals.

Bizarrely, the DNA from these extinct Siberians seems unusually similar to that of Pacific Islanders from tropical Melanesia.

The 30,000-year-old fossil was found in Denisova Cave in southern Siberia in 2008, a bone fragment that likely came from a fingertip of a young girl. [Image of finger fragment] It was discovered along with microblades (small stone blades used as tools), body ornaments of polished stone, and a molar shaped very differently from that of Neanderthals and modern humans, resembling that of much older human species, such as Homo habilis and Homo erectus. (The tooth and the finger bone apparently came from different members of the same population.)

After an international team of researchers sequenced the DNA from 40 milligrams of bone they removed from the fossil, they found the "Denisovan" (deh-NEESE-so-van) shared a common origin with Neanderthals but was genetically distinct, apparently descending from the same ancestral population of Neanderthals that had separated earlier from the ancestors of modern humans.

"It amazed me that we found this other extinct group of humans," evolutionary geneticist Svante Pääbo at the Max Planck Institute for Evolutionary Anthropology at Leipzig, Germany, told LiveScience. "When we got this little finger bone from Siberia, I was totally expecting it to be either Neanderthal or modern human. When it was something else, that was totally surprising and shocking to me."

More interbreeding

Surprisingly, their analysis found that genetic material from this sister group of Neanderthals matched 4 to 6 percent of the genomes of some modern Melanesian populations. This suggests interbreeding took place between Denisovans and the ancestors of Melanesians, just as Neanderthals appear to have interbred with the ancestors of all modern-day non-Africans.

"Instead of the clean story we used to have of modern humans migrating out of Africa and replacing Neanderthals, we now see these very intertwined story lines with more players and more interactions than we knew of before," said researcher Richard Green of the University of California, Santa Cruz.

The fact that this extinct branch of the human family tree was discovered in Siberia but contributed gene sequences to modern humans in Southeast Asia suggests it might have been widespread in Asia during the late Stone Age, said researcher David Reich, the evolutionary geneticist at Harvard Medical School who led the new population genetic analysis.

It remains uncertain whether this genetic material might have persisted in Melanesians because it provided an evolutionary edge of some sort. "We have a hard enough time learning what effects gene sequences might have when it comes to the genomes of modern humans, such as disease susceptibility - to do that with an archaic group is even harder," Reich told LiveScience.

When we met the Denisovans

These findings are adding to the complex picture of the evolutionary history of modern humans and our extinct relatives that has recently emerged, one where interbreeding has left its legacy in our DNA.

The researchers suggest an ancestral group left Africa between 300,000 and 400,000 years ago and quickly diverged, with one branch becoming the Neanderthals who spread into Europe and the other branch moving east and becoming Denisovans. When modern humans left Africa roughly 70,000 to 80,000 years ago, they first encountered the Neanderthals, with remnants of their DNA making up 1 to 4 percent of the genomes of all non-Africans. Another group of modern humans later came in contact with Denisovans.

"This study fills in some of the details, but we would like to know much more about the Denisovans and their interactions with human populations," Green said. "And you have to wonder if there were other populations that remain to be discovered. Is there a fourth player in this story?"

The researchers studiously avoid calling the Denisovans a new species or subspecies. In fact, it remains highly contentious as to whether the Neanderthals were another species altogether or were a subspecies of our species. A species is a group different enough from other groups as to be considered separate, and whose members can and do interbreed - although research has recently shown that Neanderthals (and now Denisovans) shared genes with us, so it remains an open question as to how different they were. Neanderthals and Denisovans are both called humans, however, just as all members of the genus Homo are - the controversy is over whether they should be lumped together with us anatomically modern humans or not.

Future research can investigate whether the Denisovan or Neanderthal remnants seen in modern humans provide any evolutionary advantages, Reich added.

"Maybe this is the future - reconstructing extinct relatives based not on what stone tools they made, but on their whole genomes from only little pieces of bone," Pääbo said.

The scientists detailed their findings in the Dec. 23 issue of the journal Nature.

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Age Confirmed for 'Eve,' Mother of All Humans

Wynne Parry, LiveScience Senior Writer, LiveScience.com

A maternal ancestor to all living humans called mitochondrial Eve likely lived about 200,000 years ago, at roughly the same time anatomically modern humans are believed to have emerged, a new review study confirms.

The results are based on analyses of mitochondrial DNA. Found in the energy-producing centers of cells, mitochondrial DNA is only passed down the maternal line, and can be traced back to one woman.

However, this doesn't mean she was the first modern woman, rather it indicates that only her descendants survive to the present day.

"There is always some other female that predated mitochondrial Eve, whose DNA didn't make it up to modernity," said Marek Kimmel, a professor of statistics at Rice University. "So the age of the mitochondrial Eve is always less than the age of the true, first female modern human."

A molecular clock

While most of an organism's DNA is contained in the nuclei of its cells, mitochondria also contain genetic material, but much less of it, making it easier to analyze. Mitochondrial DNA contains a region that changes rapidly and can provide a sort of molecular clock calibrated to times comparable to the age of modern humanity, making it a favorite for population geneticists, Kimmel said.

As part of the three-year project, Kimmel and Krzysztof Cyran, a Polish researcher, compared the estimates produced by about 10 genetic models intended to determine when mitochondrial Eve lived. They started with data on mitochondrial DNA previously collected from random blood donors.

Scientists know the average rate of mutation, so they can look at the genetic variation among pairs of individuals to see when their lineages diverged. But the equation becomes more complicated.

"Mutation is producing divergence, but some of the divergence is lost because of random events that occur, for example some populations become extinct," Kimmel said. As ancient modern humans dispersed, some groups settled and grew, while others became extinct.

The models make different assumptions about growth and extinction rates, which had the potential to change the estimate of mitochondrial Eve's age, the researchers found. One type of model makes the less realistic, but more manageable assumption that the human population has increased at a smooth, nearly exponential rate. Another more realistic, but more technically challenging type of model assumes the human population has grown in discrete random episodes.

An agreement

But, regardless, all of the models produced estimates placing this ancient mother's age at around 200,000 years.

"We actually show if one uses different models, one comes up with a very similar estimate, so this makes the estimate more robust," Kimmel said.

The estimates produced by models that assume population growth occurred in discrete, random bursts fell within 10 percent of each other. When taking into consideration models that assumed smooth growth, that range expanded by up to 20 percent. These models also tended to estimate that mitochondrial Eve lived earlier, according to Kimmel.

The research was published in June in the journal Theoretical Population Biology.

• Top 10 Mysteries of the First Humans 
• Gallery: Evolution's Most Extreme Mammals 
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Questions raised about 'Ardi' as man's ancestor

Malcolm Ritter, AP Science Writer

NEW YORK – Last fall, a fossil skeleton named "Ardi" shook up the field of human evolution. Now, some scientists are raising doubts about what exactly the creature from Ethiopia was and what kind of landscape it inhabited.

New critiques question whether Ardi really belongs on the human branch of the evolutionary tree, and whether it really lived in woodlands. That second question has implications for theories about what kind of environment spurred early human evolution.

The new work is being published by the journal Science, which last year declared the original presentation of the 4.4 million-year-old fossil to be the magazine's breakthrough of the year.

Ardi, short for Ardipithecus ramidus, is a million years older than the famous "Lucy" fossil. Last October, it was hailed as a window on early human evolution.

Researchers concluded that "Ardi" walked upright rather than on its knuckles like chimps, for example, and that it lived in woodlands rather than open grasslands. It didn't look much like today's chimps, our closest living relatives, even though it was closer than Lucy to the common ancestor of humans and chimps.

Such questioning isn't unusual; big scientific discoveries are typically greeted that way. Until more scientists can study the fossil and other work can be done, broad consensus may be elusive. The 2003 discovery of diminutive fossil "hobbits" in Indonesia, for example, has spurred a long-running debate about whether the hobbits were a separate species or not.

Tim White of the University of California, Berkeley, one of the scientists who described Ardi last year in Science, said he isn't surprised by this week's debate.

"It was completely expected," he said. "Any time you have something that is as different as Ardi, you're probably going to have it."

Esteban Sarmiento of the Human Evolution Foundation in East Brunswick, N.J., wrote in the new analysis that he's not convinced Ardi belongs on the evolutionary tree branch leading to modern humans.

Instead, he said in an interview, he thinks it came along earlier, before that human branch split off from the ancestors of chimps and gorillas.

The specific anatomical features of teeth, the skull and elsewhere that the researchers cited just don't make a convincing case for membership on the human branch, he argued. Some, like certain features in the wrist and where the lower jaw connects to the skull, indicate instead that Ardi arose before humans split off from African apes, he said.

In a written rebuttal in Science and in a telephone interview, White disagreed with Sarmiento's conclusion. "The evidence is very clear that in Ardipithecus, there are characteristics shared only by later hominids ... and humans," White said.

If Ardi were really ancestral to chimps, certain features of its teeth, pelvis, and skull would have had to later evolve back to their more ape-like conditions, an "evolutionary reversal that's highly unlikely," White said in an interview.

Two other experts, however, said in interviews that they think it's too early to tell where Ardi fits on the evolutionary tree.

Will Harcourt-Smith, a research associate at the American Museum of Natural History and member of the anthropology department at Lehman College in New York, said he could not say whether Sarmiento was right or wrong.

"It's early days" in the analysis of Ardi, he said. "Until there is a more complete description of the skeleton, one has to be cautious about interpreting the initial analyses one way or another... I still think it's open season."

Harcourt-Smith said he did disagree with Sarmiento's assertion that Ardi was probably too old to belong to the human branch of the evolutionary tree.

Rick Potts, head of the human origins program at the Smithsonian Institution's Natural History Museum, said Ardi is known chiefly from just one site. And it lived during a dimly understood period of evolution when there might have been "a lot of experimentation," he said.

Potts said that makes it hard to draw conclusions about how the species relates to Lucy and modern humans.

"I think it's just too soon to tell exactly where it stands in relationship to the branching point of humans from other African apes," he said.

The second critique focuses on Ardi's environment. Last year's analysis said it was predominantly a woodland setting. So that argued against the "savanna hypothesis," the idea that early human ancestors started to walk upright because they lived on grassy plains and savannas.

In this week's critique, geochemist Thure Cerling of the University of Utah and other scientists said their reading of the evidence shows Ardi roamed in a savanna with no more than 25 percent covered by a woody canopy. So they disagreed with last year's emphasis on the leafy setting.

The critique focused on evidence like analysis of ancient soils, tooth enamel from animals found at the site and tiny silica grains found in plants.

In a published rebuttal and the interview, White agreed that Ardi's environment included grasslands but said the totality of the evidence shows Ardi preferred living in its wooded areas instead.

For example, the skeleton shows adaptations for climbing and "it wasn't climbing grass," he said. And animals found with Ardi's remains are mostly woodland creatures like leaf-eating monkeys, he said.

Potts said he thinks White is right about the environment of the site in dispute. But again, he said, that's just one site, and not enough for drawing conclusions about the general environmental conditions of early human evolution — if indeed White is also right about Ardi's place on the family tree.

Online:

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http://sciencemag.org/ardipithecus

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Cal scientists unveil oldest skeleton that shares human, chimp features

Lisa M. Krieger, lkrieger@mercurynews.com, 10/01/09

A research team led by Bay Area scientists has unveiled the oldest-known member of the human family tree: a 4.4 million-year-old female skeleton named "Ardi," who shares both chimp and modern human features.

Believed to be capable of both climbing and walking, "Ardi" reveals the early evolutionary steps that our ancestors took after we diverged from our common ancestor with chimpanzees.

"It's not a chimp. It's not a human. It shows us what we used to be," said paleoanthropologist Tim White of the University of California-Berkeley, co-director of the research group that discovered and analyzed the fossils, described in a special issue of the Oct. 2 journal Science. "It bridges a gap."

In a press briefing this morning in Washington D.C., White and his team described the Ethiopian skeleton — a creature called Ardipithecus ramidus, thought to weigh 110 pounds and stand about four feet tall — that is stunningly complete, with most of skull and teeth as well as a pelvis, hands and feet.

"Ardi" and bone fragments from at least 35 related individuals were found in the 1990s. But it took 17 years for the team — 47 different scientists from ten different countries, as well as Los Alamos National Laboratory and the Berkeley Geochronology Center — to analyze and interpret the data.

Until now, the earliest known specimen of human evolution was Australopithecus, a small-brain but fully bipedal "ape-man" that lived between 4 and 1 million years ago. The most famous member of this genus was the 3.2-million-year-old skeleton nicknamed "Lucy," found in 1974.

The new skeleton is older and more primitive than Lucy, according to White, 59, who has collected fossils in the hot and scrubby region of Ethiopia since 1981. He wore a "Save UC" button in Washington D.C., decrying budget cuts to the university.

With both chimp-like and human features, "Ardi" lived in two worlds — upright but also in trees.

For instance, she was adept at efficiently climbing — but could also walk on two feet, like humans. Because she had a fully opposable grasping big toe and did not have an arched foot, she walked flat-footed. It's unlikely she could walk or run for long distances, like humans. But nor was she as agile as chimps, so could not swing through trees. She was probably a slow and careful climber.

She is thought to have been more omnivorous than chimpanzees, eating nuts, insects and small mammals in the woods.

Her lower face had a muzzle that juts out less than a chimpanzee's. Her face is in a more vertical position. Her head balanced atop the spine, as in later upright walkers. And her teeth lack the sharp canines of chimps. Her pelvis is large, like apes. But it is structured so it has a low center of gravity, so she could balance while walking. There are suggestions that her spine is long and curved, like humans.

But she is not "the missing link," a transitional creature between today's chimps and humans. This concept has been abandoned: We did not evolve from living champs or apes, but shared a common ancestor.

Nor is she this long-sought "last common ancestor." That's because she's too young; Chimps and humans are thought to have diverged between 5 and 10 million years ago. Then we went our separate ways, each taking different evolutionary trajectories.

But she's important because she is the closest we have come to this unfound "last common ancestor." She belonged to a new type of early hominid that was neither chimpanzee nor fully human.

The scientists have not fully connected the branches in the human evolutionary tree. Rather, they are focusing on the anatomical interpretation of "Ardi."

The name Ardipithecus ramidus is derived from the Ethiopian local language, Afar. "Ardi" means "ground," and "pithecus" is Greek for ape. "Ramid" means root. A literal translation of the creature is "root of the ground ape."

The fossils were found in Ethiopia's Afar Rift, about 140 miles northeast of Addis Ababa, Ethiopia's capitol. The rift is a large triangular depression, where sediments have been accumulating for millions of years. The most fossil-rich site is very extensive — transecting an ancient landscape exposed along a 41/2-mile strip — and provides a vast amount of new geological and paleobiological data.

Now parched desert, the landscape was once heavily wooded. There were fresh water springs and small patches of dense forest. The site also holds fossils of fig trees, land snails, birds such as owls and parrots, small mammals like mice and bats, as well as rhinos, bears, elephants, giraffes, antelopes and two kinds of monkeys.

The discovery of "Ardi" in woodlands refutes the once-popular hypothesis that early humans took their first steps in open grasslands, say scientists.

The first glimpse of the creature came in 1992 when a former UC-Berkeley grad student, Gen Suwa, saw a glint in desert pebbles — the polished surface of a tooth root from a hominim molar. The team immediately got on their hands and knees and searched for more fossils. Within days, they had found a lower jaw of a child.

In 1994, Berkeley graduate student Yohanes Haile-Selassie of Ethiopia crawled up an embankment in the region and found two pieces of a bone from the palm of a hand.

This was soon followed by the discovery of 110 other skeletal fragments, as well as 150,000 specimens of fossil plants and animals.

"This team seems to suck fossils out of the earth," anatomist C. Owen Lovejoy of Kent State University, also part of the team, told the journal Science.

But the bones were in terrible condition, trampled and scattered. White called them "road kill." So entire blocks of fossil-rich rock were moved to the National Museum of Ethiopia in Addis Ababa. It took years to remove the clay from the fragile fossils.

Many high-tech instruments were used in the analysis, such as mass spectrometers to measure the age of the rock and micro-CT scanners to study the inner anatomy of bones and teeth. Electron microscopes revealed the tiny surface details of the fossils.

The lava and ashes were shipped from Africa to California for dating analysis.

At Los Alamos National Laboratory, Giday WoldeGabriel helped produce a detailed chemical profile of the major constituents of the glass shards found in the volcanic ash surrounding the fossils.

The Berkeley Geochronology Center did paleomagnetic lab work, using a dating technique that determines how much time has elapsed since the eruption of volcanic ash.

"Because they were sandwiched between two volcanic horizons with virtually indistinguishable dates, the thousands of fossils collected at Aramis are among the best calibrated in the world, at 4.4 million years ago," said project geochronologist Paul Renne of the Berkeley Geochronology Center.

UC-Berkeley was critical to the fossil-mining operation that discovered "Ardi," said White.

White came to UC-Berkeley because of its reputation in the exploration of human origins. He became interested in the field as a teenager after reading the 1965 Time/Life Nature Library book, "Early Man," written by famed Berkeley anthropologist Francis Clark Howell. Once at Berkeley, White studied under Howell and esteemed African archeologist J. Desmond Clark.

About one-quarter of the project's 47 authors were educated or trained at UC-Berkeley, he said. The university also trained the first generation of African scholars in the field. Africans now play a critical role in studying and preserving this cradle of humankind.

"We are very proud of Cal," said White. "This is what universities can achieve — and especially the public museums that support and produce this research, which are under great stress today.

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