Ahira's Hangar

Researcher: Birds hunted ancient man

Thursday, January 12, 2006; Posted: 1:17 p.m. EST (18:17 GMT)

Paleo-anthropologist Lee Berger, with replicas of a part of the Taung child skull and a predatory bird.
JOHANNESBURG, South Africa (AP) -- An American researcher said Thursday his investigation into the death nearly 2 million years ago of an ape-man shows human ancestors were hunted by birds.

"These types of discoveries give us real insight into the past lives of these human ancestors, the world they lived in and the things they feared," Lee Berger, a paleo-anthropologist at Johannesburg's University of Witwatersrand, said as he presented his conclusions about a mystery that has been debated since the remains of the possible human ancestor known as the Taung child were discovered in 1924.

The Taung child's discovery led to the search for human origins in Africa, instead of in Asia or Europe as once theorized. Researchers regard the fossil of the ape-man, or australopethicus africanus, as evidence of the "missing link" in human evolution.

Researchers had speculated the Taung child was killed by a leopard or saber-toothed feline. But 10 years ago, Berger and fellow researcher Ron Clarke submitted the theory the hunter was a large predatory bird, based on the fact most of the other fossils found at the same site were small monkeys that showed signs of having been killed by a predatory bird.

Berger and Clarke had until now been unable to show damage on the child's skull that could have been done by a bird.

Five months ago, Berger read an Ohio State University study of the hunting abilities of modern eagles in West Africa believed similar to predatory birds of the Taung child's era.

The Ohio State study determined that eagles would swoop down, pierce monkey skulls with their thumb-like back talons, then hover while their prey died before returning to tear at the skull. Examination of thousands of monkey remains produced a pattern of damage done by birds, including holes and ragged cuts in the shallow bones behind the eye sockets.

Berger went back to the Taung skull, and found traces of the ragged cuts behind the eye sockets. He said none of the researchers who had for decades been debating how the child died had noticed the eye socket damage before.

Berger concluded man's ancestors had to survive not just being hunted from the ground, but from the air. Such discoveries are "key to understanding why we humans today view the world the way we do," he said.

Berger's research has been reviewed by others and is due to appear in the February edition of the American Journal of Physical Anthropology.

Copyright 2006 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.

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Our lives are the songs that sing the universe into existence.~David Zindell
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Could Ethiopian skull be missing link?
Scientists believe find could link homo erectus and modern man

Saturday, March 25, 2006; Posted: 7:13 p.m. EST (00:13 GMT)
ADDIS ABABA, Ethiopia (AP) -- Scientists in northeastern Ethiopia said Saturday that they have discovered the skull of a small human ancestor that could be a missing link between the extinct Homo erectus and modern man.

The hominid cranium -- found in two pieces and believed to be between 500,000 and 250,000 years old -- "comes from a very significant period and is very close to the appearance of the anatomically modern human," said Sileshi Semaw, director of the Gona Paleoanthropological Research Project in Ethiopia.

Archaeologists found the early human cranium five weeks ago at Gawis in Ethiopia's northeastern Afar region, Sileshi said.

Several stone tools and fossilized animals including two types of pigs, zebras, elephants, antelopes, cats, and rodents were also found at the site.

Sileshi, an Ethiopian paleoanthropologist based at Indiana University, said most fossil hominids are found in pieces but the near-complete skull -- a rare find -- provided a wealth of information.

"The Gawis cranium provides us with the opportunity to look at the face of one of our ancestors," the archaeology project said in a statement.

Homo erectus, which many believe was an ancestor of modern Homo sapiens, is thought to have died out 100,000 to 200,000 years ago.

The cranium dates to a time about which little is known -- the transition from African Homo erectus to modern humans. The fossil record from Africa for this period is sparse and most of the specimens poorly dated, project archaeologists said.

The face and cranium of the fossil are recognizably different from those of modern humans, but bear unmistakable anatomical evidence that it belongs to the modern human's ancestry, Sileshi said.

"A good fossil provides anatomical evidence that allows us to refine our understanding of evolution. A great fossil forces us to re-examine our views of human origins. I believe the Gawis cranium is a great fossil," said Scott Simpson, a project paleontologist from Case Western Reserve University School of Medicine at Cleveland, Ohio.

Scientists conducting surveys in the Gawis River drainage basin found the skull in a small gully, the project statement said.

"This is really exciting because it joins a limited number of fossils which appear to be evolutionary between Homo erectus and our own species Homo sapiens," said Eric Delson, a paleoanthropologist at Lehman College of the City University of New York, who was not involved in the discovery but has followed the project.

Homo erectus left Africa about 2 million years ago and spread across Asia from Georgia in the Caucasus to China and Indonesia. It first appeared in Africa between 1 million and 2 million years ago.

Between 1 million and perhaps 200,000 years ago, one or more species existed in Africa that gave rise to the earliest members of our own species Homo sapiens -- between 150,000 and 200,000 years ago.

Delson said the fossil found in Ethiopia "might represent a population broadly ancestral to modern humans or it might prove to be one of several side branches which died out without living descendants."

Copyright 2006 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.

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Our lives are the songs that sing the universe into existence.~David Zindell
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Fossil connects human evolution dots

Wednesday, April 12, 2006; Posted: 1:06 p.m. EDT (17:06 GMT)
WASHINGTON (AP) -- The latest fossil unearthed from a human ancestral hot spot in Africa allows scientists to link together the most complete chain of human evolution so far.

The 4.2 million-year-old fossil discovered in northeastern Ethiopia helps scientists fill in the gaps of how human ancestors made the giant leap from one species to another.

That's because the newest fossil, the species Australopithecus anamensis, was found in the region of the Middle Awash -- where seven other human-like species spanning nearly 6 million years and three major phases of human development were previously discovered.

"We just found the chain of evolution, the continuity through time," study co-author and Ethiopian anthropologist Berhane Asfaw said in a phone interview from Addis Ababa. "One form evolved to another. This is evidence of evolution in one place through time."

The findings were reported Thursday in the scientific journal Nature.

The species anamensis is not new, but its location is what helps explain the shift from one early phase of human-like development to the next, scientists say. All eight species were within an easy day's walk of each other.

Until now, what scientists had were snapshots of human evolution scattered around the world. Finding everything all in one general area makes those snapshots more of a mini home movie of evolution.

"It's like 12 frames of a home movie, but a home movie covering 6 million years," said study lead author Tim White, co-director of Human Evolution Research Center at University of California at Berkeley.

"The key here is the sequences," White said. "It's about a mile thickness of rocks in the Middle Awash and in it we can see all three phases of human evolution."

Modern man belongs to the genus Homo, which is a subgroup in the family of hominids. What evolved into Homo was likely the genus Australopithecus (once called "man-ape"), which includes the famed 3.2 million-year-old "Lucy" fossil found three decades ago.

A key candidate for the genus that evolved into Australopithecus is called Ardipithecus. And Thursday's finding is important in bridging -- but not completely -- the gap between Australopithecus and Ardipithecus.

In 1994, a 4.4 million-year-old partial skeleton of the species Ardipithecus ramidus -- the most recent Ardipithecus species -- was found about six miles from the latest discovery.

"This appears to be the link between Australopithecus and Ardipithecus as two different species," White said. The major noticeable difference between the phases of man can be seen in Australopithecus' bigger chewing teeth to eat harder food, he said.

While it's looking more likely, it is not a sure thing that Ardipithecus evolved into Australopithecus, he said. The finding does not completely rule out Ardipithecus dying off as a genus and Australopithecus developing independently.

The connections between Ardipithecus and Australopithecus have been theorized since an anamensis fossil was first found in Kenya 11 years ago. This draws the lines better, said Alan Walker of Penn State University, who found the first anamensis and is not part of White's team.

Rick Potts, director of the Smithsonian's Human Origins Program, agreed: "For those people who are tied up in doing the whole human family tree, being able to connect the branches is a very important thing to do."

Copyright 2006 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.

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Our lives are the songs that sing the universe into existence.~David Zindell
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DNA study: Human-chimp split was messy

Wednesday, May 17, 2006; Posted: 1:03 p.m. EDT (17:03 GMT)
NEW YORK (AP) -- Humans and chimps diverged from a single ancestral population through a complex process that took 4 million years, according to a new study comparing DNA from the two species.

By analyzing about 800 times more DNA than previous studies of the human-chimp split, researchers from the Broad Institute of MIT and Harvard were able to learn not just when, but a little bit about how the sister species arose.

"For the first time we're able to see the details written out in the DNA," said Eric Lander, founding director of the Broad Institute. "What they tell us at the least is that the human-chimp speciation was very unusual."

The researchers hypothesize that an ancestral ape species split into two isolated populations about 10 million years ago, then got back together after a few thousand millennia. At that time the two groups, though somewhat genetically different, would have mated to form a third, hybrid population. That population could have interbred with one or both of its parent populations. Then, at some point after 6.3 million years ago, two distinct lines arose.

Some experts in human evolution are skeptical of that precise scenario, but nevertheless impressed with the study.

"It's a totally cool and extremely clever analysis," said Daniel Lieberman, a professor of biological anthropology at Harvard. "My problem is imagining what it would be like to have a bipedal hominid and a chimpanzee viewing each other as appropriate mates, not to put it too crudely."

Past studies that compared human and chimp DNA could only offer a point estimate of how long ago the two species split by averaging the amount of divergence in their genes. Generally, those studies come up with a figure of about 7 million years ago.

But since the completion of the chimpanzee genome project in September it is possible to look at how specific sections of the genetic code have evolved. The Broad Institute study, which will be published in a future issue of the journal Nature, is one of the first to do that.

"There are a lot of big surprises here," Lander said.

For one thing, the new data suggest the human-chimp split was much closer to the present than the 7 million year date that fossils and previous studies indicate -- certainly no earlier than 6.3 million years ago, and more likely in the neighborhood of 5.4 million.

The data also show that the human-chimp split probably took millions of years. That's because in some parts of the DNA sequence the genetic difference between humans and chimps is so large that those genes must have been isolated from each other nearly 10 million years ago. But in other places the human and chimp lines are so close that they appear to have still been swapping genetic material at least until 6.3 million years ago.

One of those areas is the X-chromosome, which is intriguing.

"The genes that are a barrier to speciation tend to be on the X-chromosome," said David Reich, the main author of the study.

Copyright 2006 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.

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Skeleton sheds light on ape-man species
POSTED: 1:13 p.m. EDT, September 20, 2006

NEW YORK (AP) -- Scientists have discovered a remarkably complete skeleton of a 3-year-old female from the ape-man species represented by "Lucy."

The discovery should fuel a contentious debate about whether this species, which walked upright, also climbed and moved through trees easily like an ape.

The remains are 3.3 million years old, making them the oldest known skeleton of such a youthful human ancestor.

"It's pretty unbelievable" to find such a complete fossil from that long ago, said scientist Fred Spoor. "It's a once-in-a-lifetime find."

Spoor, professor of evolutionary anatomy at University College London, describes the fossil in Thursday's issue of the journal Nature with Zeresenay Alemseged of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and other scientists.

The skeleton was discovered in 2000 in northeastern Ethiopia. Scientists have spent five painstaking years removing the bones from sandstone, and the job will take years more to complete.

Judging by how well it was preserved, the skeleton may have come from a body that was quickly buried by sediment in a flood, the researchers said.

The creature was a member of Australopithecus afarensis, which lived in Africa between about 4 million and 3 million years ago. The most famous afarensis is Lucy, discovered in Ethiopia in 1974, which lived about 100,000 years after the newfound specimen.

Most scientists believe afarensis stood upright and walked on two feet, but they argue about whether it had ape-like agility in trees.

That climbing ability would require anatomical equipment like long arms, and afarensis had arms that dangled down to just above the knees. The question is whether such features indicate climbing ability or just evolutionary baggage.

Spoor said so far, analysis of the new fossil hasn't settled the argument but does seem to indicate some climbing ability.

While the lower body is very human-like, he said, the upper body is ape-like:


*The shoulder blades resemble those of a gorilla rather than a modern human.


*The neck seems short and thick like a great ape's, rather than the more slender version humans have to keep the head stable while running.


*The organ of balance in the inner ear is more ape-like than human.


*The fingers are very curved, which could indicate climbing ability, "but I'm cautious about that," Spoor said. Curved fingers have been noted for afarensis before, but their significance is in dispute.

A big question is what the foot bones will show when their sandstone casing is removed, he said. Will there be a grasping big toe like the opposable thumb of a human hand? Such a chimp-like feature would argue for climbing ability, he said.

Yet, to resolve the debate, scientists may have to find a way to inspect vanishingly small details of such old bones, to get clues to how those bones were used in life, he said.

Bernard Wood of George Washington University, who didn't participate in the discovery, said in an interview that the fossil provides strong evidence of climbing ability. But he also agreed that it won't settle the debate among scientists, which he said "makes the Middle East look like a picnic."

Overall, he wrote in a Nature commentary, the discovery provides "a veritable mine of information about a crucial stage in human evolutionary history."

The fossil revealed just the second hyoid bone to be recovered from any human ancestor. This tiny bone, which attaches to the tongue muscles, is very chimp-like in the new specimen, Spoor said.

While that doesn't directly reveal anything about language, it does suggest that whatever sounds the creature made "would appeal more to a chimpanzee mother than a human mother," Spoor said.

The fossil find includes the complete skull, including an impression of the brain and the lower jaw, all the vertebrae from the neck to just below the torso, all the ribs, both shoulder blades and both collarbones, the right elbow and part of a hand, both knees and much of both shin and thigh bones.

One foot is almost complete, providing the first time scientists have found an afarensis foot with the bones still positioned as they were in life, Spoor said.

The work was funded by the National Geographic Society, the Institute of Human Origins at Arizona State University, the Leakey Foundation and the Planck institute.

Copyright 2006 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.

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How Our Ancestors Were Like Gorillas
ScienceDaily (Nov. 30, 2007) — New research shows that some of our closest extinct relatives had more in common with gorillas than previously thought. Dr Charles Lockwood, UCL Department of Anthropology and lead author of the study, said: "When we examined fossils from 1.5 to 2 million years ago we found that in one of our close relatives the males continued to grow well into adulthood, just as they do in gorillas. This resulted in a much bigger size difference between males and females than we see today.

"It's common knowledge that boys mature later than girls, but in humans the difference is actually much less marked than in some other primates. Male gorillas continue to grow long after their wisdom teeth have come through, and they don't reach what is referred to as dominant "silverback" status until many years after the females have already started to have offspring. Our research makes us think that, in this fossil species, one older male was probably dominant in a troop of females. This situation was risky for the males and they suffered high rates of predation as a result of both their social structure and pattern of growth."

The research used 35 fossilised specimens of Paranthropus robustus, an extinct relative of Homo sapiens which existed almost two million years ago. The fossils came from the palaeontological sites of Swartkrans, Drimolen and Kromdraii, all of which are in South Africa's Cradle of Humankind World Heritage Site near Johannesburg.

The research was inspired by earlier discoveries at Drimolen by Dr Andre Keyser, one of the co-authors of the study. Dr Colin Menter, from the University of Johannesburg and co-director of current fieldwork at Drimolen, explains: "Discoveries at this site showed us that sex differences in Paranthropus robustus were greater than we had previously thought. While there are some specimens from Drimolen that are just as large and robust as those from other sites like Swartkrans, there is a complete female skull that is distinctly smaller than the other, well-preserved specimens of the species."

Jacopo Moggi-Cecchi, based at the University of Florence and an expert on fossil teeth, participated in the study and says: "It takes large samples of fossils to ask questions about variation and growth, and it's really a tribute to fieldworkers such as Robert Broom and Bob Brain [who worked at Swartkrans] that this research could even take place. It's also an example of why we need to continue to look for fossils after we think we know what a species is -- more specimens allow us to answer more interesting questions. Even isolated teeth can give us new insights into what variation means."

Dr Lockwood adds: "The pattern of growth also gives a better understanding of who is male and who is female in this sample of skulls and it turns out that there are far more males in the fossil sample. Because fossils from the most prolific site, Swartkrans, are thought to have been deposited by predators such as leopards and hyenas, it appears that males were getting killed more often than females.

"Basically, males had a high-risk, high-return lifestyle in this species. They most likely left their birth groups at about the time they reached maturity, and it was a long time before they were mature enough to attract females and establish a new group. Some of them were killed by predators before they got the chance."

A final point made by the researchers is that not all fossil hominin samples show the same patterns, and it is quite possible that further work will reveal clear diversity in social structure between human ancestors, in the same way that one sees differences among apes such as chimpanzees, bonobos, gorillas, and orangutans. This research will help us to understand how human social structure evolved.

This research was published in the journal Science on November 30, 2007.

Research at Drimolen has been funded by the Leakey Foundation, the Department of Science and Technology in South Africa, the Italian Ministry of Foreign Affairs, and the Italian Cultural Institute in Pretoria. The Royal Society supported Charles Lockwood's work in South Africa.

Fossils are housed at the University of the Witwatersrand in Johannesburg and the Transvaal Museum (Northern Flagship Institution), Pretoria.

Adapted from materials provided by University College London, via EurekAlert!, a service of AAAS.

Neanderthal Children Grew Up Fast
ScienceDaily (Dec. 5, 2007) — An international European research collaboration led by scientists at the Max Planck Institute for Evolutionary Anthropology reports evidence for a rapid developmental pattern in a 100,000 year old Belgian Neanderthal (Homo neanderthalensis).

The evolution of human intelligence
A new report details how the team used growth lines both inside and on the surfaces of the child’s teeth to reconstruct tooth formation time and its’ age at death.

Scientists found differences in the duration of tooth growth in the Neanderthal when compared to modern humans, with the former showing shorter times in most cases. This faster growth resulted in a more advanced pattern of dental development than in fossil and living members of our own species (Homo sapiens).

The Scladina juvenile, which appears to be developmentally similar to a 10-12 year old human, was estimated to be in fact about 8 years old at death. This pattern of development appears to be intermediate between early members of our genus (e.g., Homo erectus) and living people, suggesting that the characteristically slow development and long childhood is a recent condition unique to our own species.

Neanderthal life history, or the timing of developmental and reproductive events, has been under great debate during the past few decades. Across primates, tooth development, specifically the age of molar eruption, is related to other developmental landmarks such as weaning and first reproduction.

Scientists have previously found evidence to both support and refute the idea that Neanderthals grew up differently than our own species. In this new study, researchers used information from the inside of a molar tooth, coupled with data from micro-computed tomography (micro-CT), as well as evidence of developmental stress on the outsides of tooth crowns and roots.

This yields the first chronology, or time sequence, for Neanderthal tooth growth, which differs from living humans. The Scladina Neanderthal grew teeth over a shorter period of time, and has more teeth erupted (present in the mouth), than similarly-aged fossil or living humans (Homo sapiens).

This suggests that other aspects of physical development were likely more rapidly achieved as well, implying significant differences in the behaviour or social organization of these ancient humans.

Journal reference: Tanya M. Smith, Michel Toussaint, Donald J. Reid, Anthony J. Olejniczak, Jean-Jacques Hublin, Rapid Dental Development in a Middle Paleolithic Belgian Neanderthal, Proceedings of the National Academy of Sciences USA December 2007

Adapted from materials provided by Max-Planck-Gesellschaft.

Geologists Say 'Wall Of Africa' Allowed Humanity To Emerge
ScienceDaily (Dec. 22, 2007) — Scientists long have focused on how climate and vegetation allowed human ancestors to evolve in Africa. Now, University of Utah geologists are calling renewed attention to the idea that ground movements formed mountains and valleys, creating environments that favored the emergence of humanity.



"Tectonics [movement of Earth's crust] was ultimately responsible for the evolution of humankind," Royhan and Nahid Gani of the university's Energy and Geoscience Institute write in the January, 2008, issue of Geotimes, published by the American Geological Institute.

They argue that the accelerated uplift of mountains and highlands stretching from Ethiopia to South Africa blocked much ocean moisture, converting lush tropical forests into an arid patchwork of woodlands and savannah grasslands that gradually favored human ancestors who came down from the trees and started walking on two feet -- an energy-efficient way to search larger areas for food in an arid environment.

In their Geotimes article, the Ganis -- a husband-and-wife research team who met in college in their native Bangladesh -- describe this 3,700-mile-long stretch of highlands and mountains as "the Wall of Africa." It parallels the famed East African Rift valley, where many fossils of human ancestors were found.

"Because of the crustal movement or tectonism in East Africa, the landscape drastically changed over the last 7 million years," says Royhan Gani (pronounced rye-hawn Go-knee), a research assistant professor of civil and environmental engineering. "That landscape controlled climate on a local to regional scale. That climate change spurred human ancestors to evolve from apes."

Hominins -- the new scientific word for humans (Homo) and their ancestors (including Ardipithecus, Paranthropus and Australopithecus) -- split from apes on the evolutionary tree roughly 7 million to 4 million years ago. Royhan Gani says the earliest undisputed hominin was Ardipithecus ramidus 4.4 million years ago. The earliest Homo arose 2.5 million years ago, and our species, Homo sapiens, almost 200,000 years ago.

Tectonics -- movements of Earth's crust, including its ever-shifting tectonic plates and the creation of mountains, valleys and ocean basins -- has been discussed since at least 1983 as an influence on human evolution.

But Royhan Gani says much previous discussion of how climate affected human evolution involves global climate changes, such as those caused by cyclic changes in Earth's orbit around the sun, and not local and regional climate changes caused by East Africa's rising landscape.

A Force from within the Earth

The geological or tectonic forces shaping Africa begin deep in the Earth, where a "superplume" of hot and molten rock has swelled upward for at least the past 45 million years. This superplume and its branching smaller plumes help push apart the African and Arabian tectonic plates of Earth's crust, forming the Red Sea, Gulf of Aden and the Great Rift Valley that stretches from Syria to southern Africa.

As part of this process, Africa is being split apart along the East African Rift, a valley bounded by elevated "shoulders" a few tens of miles wide and sitting atop "domes" a few hundreds of miles wide and caused by upward bulging of the plume.

The East African Rift runs about 3,700 miles from the Ethiopian Plateau south-southwest to South Africa's Karoo Plateau. It is up to 370 miles wide and includes mountains reaching a maximum elevation of about 19,340 feet at Mount Kilimanjaro.

The rift "is characterized by volcanic peaks, plateaus, valleys and large basins and freshwater lakes," including sites where many fossils of early humans and their ancestors have been found, says Nahid Gani (pronounced nah-heed go-knee), a research scientist. There was some uplift in East Africa as early as 40 million years ago, but "most of these topographic features developed between 7 million and 2 million years ago."

A Wall Rises and New Species Evolve

"Although the Wall of Africa started to form around 30 million years ago, recent studies show most of the uplift occurred between 7 million and 2 million years ago, just about when hominins split off from African apes, developed bipedalism and evolved bigger brains," the Ganis write.

"Nature built this wall, and then humans could evolve, walk tall and think big," says Royhan Gani. "Is there any characteristic feature of the wall that drove human evolution?"

The answer, he believes, is the variable landscape and vegetation resulting from uplift of the Wall of Africa, which created "a topographic barrier to moisture, mostly from the Indian Ocean" and dried the climate. He says that contrary to those who cite global climate cycles, the climate changes in East Africa were local and resulted from the uplift of different parts of the wall at different times.

Royhan Gani says the change from forests to a patchwork of woodland and open savannah did not happen everywhere in East Africa at the same time, and the changes also happened in East Africa later than elsewhere in the world.

The Ganis studied the roughly 300-mile-by-300-mile Ethiopian Plateau -- the most prominent part of the Wall of Africa. Previous research indicated the plateau reached its present average elevation of 8,200 feet 25 million years ago. The Ganis analyzed rates at which the Blue Nile River cut down into the Ethiopian Plateau, creating a canyon that rivals North America's Grand Canyon. They released those findings in the September 2007 issue of GSA Today, published by the Geological Society of America.

The conclusion: There were periods of low-to-moderate incision and uplift between 29 million and 10 million years ago, and again between 10 million and 6 million years ago, but the most rapid uplift of the Ethiopian Plateau (by some 3,200 vertical feet) happened 6 million to 3 million years ago.

The Geotimes paper says other research has shown the Kenyan part of the wall rose mostly between 7 million and 2 million years ago, mountains in Tanganyika and Malawi were uplifted mainly between 5 million and 2 million years ago, and the wall's southernmost end gained most of its elevation during the past 5 million years.

"Clearly, the Wall of Africa grew to be a prominent elevated feature over the last 7 million years, thereby playing a prominent role in East African aridification by wringing moisture out of monsoonal air moving across the region," the Ganis write. That period coincides with evolution of human ancestors in the area.

Royhan Gani says the earliest undisputed evidence of true bipedalism (as opposed to knuckle-dragging by apes) is 4.1 million years ago in Australopithecus anamensis, but some believe the trait existed as early as 6 million to 7 million years ago.

The Ganis speculate that the shaping of varied landscapes by tectonic forces -- lake basins, valleys, mountains, grasslands, woodlands -- "could also be responsible, at a later stage, for hominins developing a bigger brain as a way to cope with these extremely variable and changing landscapes" in which they had to find food and survive predators.

For now, Royhan Gani acknowledges the lack of more precise timeframes makes it difficult to link specific tectonic events to the development of upright walking, bigger brains and other key steps in human evolution.

"But it all happened within the right time period," he says. "Now we need to nail it down."

Adapted from materials provided by University of Utah, via EurekAlert!, a service of AAAS.

Ancient 'Out Of Africa' Migration Left Stamp On European Genetic Diversity
ScienceDaily (Feb. 22, 2008) — Human migration from Africa to Europe more than 30,000 years ago appears to have left a mark on the genes of Europeans today.

A Cornell-led study, reported in the Feb. 21 issue of the journal Nature, compared more than 10,000 sequenced genes from 15 African-Americans and 20 European-Americans. The results suggest that European populations have proportionately more harmful variations, though it is unclear what effects these variations actually may have on the overall health of Europeans.

Computer simulations suggest that the first Europeans comprised small and less diverse populations. That would have allowed mildly harmful genetic variations within those populations to become more frequent over time, the researchers report.

"What we may be seeing is a 'population genetic echo' of the founding of Europe," said Carlos Bustamante, assistant professor of biological statistics and computational biology at Cornell and senior co-author with Andrew Clark, a professor of molecular biology and genetics.

"Since we tend to think of European populations as quite large, we did not expect to see a significant difference in the distribution of neutral and deleterious variation between the two populations," said Bustamante. "It was quite surprising, but when we cross-checked our results to data sets gathered by other groups, we found the same trend."

The researchers focused on single nucleotide polymorphisms (SNPs), where a single DNA base pair (the smallest structural unit) in a gene's sequence had been altered. Genetic variations were classified as to whether a SNP was found in one or both populations. Some of these genetic changes led to amino acid changes in the proteins that the genes express, while others had no effect.

Collaborators at Max Planck Institute in Tübingen, Germany, and Harvard Medical School analyzed the amino acid changes and used a computer algorithm to predict whether the changes alter a protein's structure or function, and classified the changes into three categories: benign, possibly damaging or probably damaging.

Using that information, the Cornell group found that the European sample, while showing overall less genetic variation, had proportionately more amino acid changes and proportionately more harmful amino acid single nucleotide polymorphisms than the African sample.

"It's difficult to tell what the precise impact that a higher proportion of deleterious single nucleotide polymorphisms in the population will have on the average person's health," said Kirk Lohmueller, a graduate student in both Bustamante's and Clark's labs and the paper's lead author. "More detailed studies that involve sequencing many individuals both with and without certain diseases would better enable us to get at this question."

Future research may also reveal similar signatures as other populations left Africa for other geographic destinations.

Other Cornell co-authors include Amit Indap, Adam Boyko and Ryan Hernandez as well as Rasmus Nielsen, a former Cornell faculty member now at the University of Copenhagen, and Melissa Hubisz, a former Cornell programmer now at the University of Chicago. Celera Diagnostics performed the gene sequences.

The study was funded by the National Institutes of Health and National Science Foundation.

Adapted from materials provided by Cornell University.

Upright Walking Began 6 Million Years Ago, Thigh Bone Comparison Suggests
ScienceDaily (Mar. 21, 2008) — A shape comparison of the most complete fossil femur (thigh bone) of one of the earliest known pre-humans, or hominins, with the femora of living apes, modern humans and other fossils, indicates the earliest form of bipedalism occurred at least six million years ago and persisted for at least four million years. William Jungers, Ph.D., of Stony Brook University, and Brian Richmond, Ph.D., of George Washington University, say their finding indicates that the fossil belongs to very early human ancestors, and that upright walking is one of the first human characteristics to appear in our lineage, right after the split between human and chimpanzee lineages. Their findings are published in the March 21 issue of the journal Science.


The research is the first thorough quantitative analysis of the Orrorin tugenensis fossil – a fragmentary piece of femur – which was discovered in Kenya in 2000 by a French research team. Dr. Jungers, Chair of Anatomical Sciences at SBU School of Medicine, and Dr. Richmond, Associate Professor of Anthropology at GWU and a member of GWU’s Center for the Advanced Study of Hominid Paleobiology, completed a multivariate analysis of the proximal femora shape of a young adult O. tugenensis that enabled them to pinpoint the pattern of bipedal gait for this controversial hominin. Their analysis included a large and diverse sample of apes, other early hominins, including Australopithecus, and modern humans of all body sizes.

“This research solidifies the evidence that the human lineage split off as far back as six million years ago, that we share ancestry with Orrorin, and that our ancestors were walking upright at the time,” says Dr. Richmond. “These answers were not clear before this analysis.”

“Our study confirms that as early as six million years ago, basal hominins in Africa were already similar to later australopithecines in their anatomy and inferred locomotor biomechanics,” adds Dr. Jungers. “At the same time, by way of the analysis, we see no special phylogenetic connection between Orrorin and our own genus, Homo.”

In “Orrorin tugenensis Femoral Morphology and the Evolution of Hominin Bipedalism,” the authors articulate that the analysis and morphological comparisons among femora from the fossils showed that O. tugenensis is distinct from those of modern humans and the great apes in having a long, anteroposteriorly narrow neck and wide proximal shaft. Early Homo femora have larger heads and broader necks compared to early hominins. In addition to these features, modern human femora have short necks and mediolaterally narrow shafts.

The challenge ahead, explains Dr. Jungers, is “to identify what precipitated the change from this ancient and successful adaptation of upright walking, and climbing, to our own obligate form of bipedalism.”

Adapted from materials provided by Stony Brook University Medical Center.