Saturday, 19 December 2009

Why Does a Human Baby Need a Full Year Before Starting to Walk?

Why does a human baby need a full year before it can start walking, while a newborn foal gets up on its legs almost directly after birth? Scientist have assumed that human motor development is unique because our brain is unusually complex and because it is particularly challenging to walk on two legs. But now a research group at Lund University in Sweden has shown that human babies in fact start walking at the same stage in brain development as most other walking mammals, from small rodents to elephants.

The Lund group consists of neurophysiologists Martin Garwicz and Maria Christensson and developmental psychologist Elia Psouni. Contrary to convention, they used conception and not birth as the starting point of motor development in their comparison between different mammals. This revealed astonishing similarities among species that diverged in evolution as much as 100 million years ago.

Humans certainly have more brain cells and bigger brains than most other terrestrial mammalian species, but with respect to walking, brain development appears to be similar for us and other mammals. Our study demonstrates that the difference is quantitative, not qualitative, says Martin Garwicz.
Based on knowledge about development in other mammals it is therefore possible to actually predict with high precision when human babies will start to walk. This is a very unexpected and provocative finding.
The notion that humans have a unique position among mammals is not only deeply rooted among lay people, but is also reflected in fundamental assumptions in different research fields related to human development and human brain evolution.
"Our study strongly contradicts this assumption and thereby sheds new light on theories in, for instance, evolutionary and developmental biology," says Martin Garwicz. "On the other hand, our findings fit well with the substantial similarities between the genomes of different mammals. Perhaps these similarities are after all not that surprising -- although the end products 'human' and 'rat' may be very different, our study suggests that the building blocks and principles for how these building blocks interact with one another during development could be the same."
The study originated in an attempt by the group to translate behavioral milestones of motor development between two distantly related species. The similarities in relative developmental time courses between the two species were so striking that the scientists started to wonder whether the regularity applied to other mammals and ultimately also to humans.
The Lund group has now compared 24 species, which together represent the majority of existing walking mammals. Some, like the great apes, are closely related to us evolutionarily while others, such as rodents, hoofed animals, and elephants, diverged from our evolutionary path about 90-100 million years ago.
Despite this, and regardless of differences in various species' brain and body size, gestation time, and brain maturity at birth, the comparison shows that the young from all species start walking at the same relative time point in brain development. Humans may be unique, but not in this particular way. When the nervous system has reached a given level of maturity, you learn to walk, whether you are a hedgehog, a foal, or a human baby

Daily Science :adapted from materials provided by Lund University, via AlphaGalileo. 

Monday, 23 November 2009

'Hobbits' are a new human species -- according to the statistical analysis of fossils

Homo floresiensis not diseased sub-population of healthy humans

Researchers from Stony Brook University Medical Center in New York have confirmed that Homo floresiensis is a genuine ancient human species and not a descendant of healthy humans dwarfed by disease. Using statistical analysis on skeletal remains of a well-preserved female specimen, researchers determined the "hobbit" to be a distinct species and not a genetically flawed version of modern humans. Details of the study appear in the December issue of Significance, the magazine of the Royal Statistical Society, published by Wiley-Blackwell.
In 2003 Australian and Indonesian scientists discovered small-bodied, small-brained, hominin (human-like) fossils on the remote island of Flores in the Indonesian archipelago. This discovery of a new human species called Homo floresiensis has spawned much debate with some researchers claiming that the small creatures are really modern humans whose tiny head and brain are the result of a medical condition called microcephaly.
Researchers William Jungers, Ph.D., and Karen Baab, Ph.D. studied the skeletal remains of a female (LB1), nicknamed "Little Lady of Flores" or "Flo" to confirm the evolutionary path of the hobbit species. The specimen was remarkably complete and included skull, jaw, arms, legs, hands, and feet that provided researchers with integrated information from an individual fossil.
The cranial capacity of LB1 was just over 400 cm, making it more similar to the brains of a chimpanzee or bipedal "ape-men" of East and South Africa. The skull and jawbone features are much more primitive looking than any normal modern human. Statistical analysis of skull shapes show modern humans cluster together in one group, microcephalic humans in another and the hobbit along with ancient hominins in a third.
Due to the relative completeness of fossil remains for LB1, the scientists were able to reconstruct a reliable body design that was unlike any modern human. The thigh bone and shin bone of LB1 are much shorter than modern humans including Central African pygmies, South African KhoeSan (formerly known as 'bushmen") and "negrito" pygmies from the Andaman Islands and the Philippines. Some researchers speculate this could represent an evolutionary reversal correlated with "island dwarfing." "It is difficult to believe an evolutionary change would lead to less economical movement," said Dr. Jungers. "It makes little sense that this species re-evolved shorter thighs and legs because long hind limbs improve bipedal walking. We suspect that these are primitive retentions instead."
Further analysis of the remains using a regression equation developed by Dr. Jungers indicates that LB1 was approximately 106 cm tall (3 feet, 6 inches)—far smaller than the modern pygmies whose adults grow to less than 150 cm (4 feet, 11 inches). A scatterplot depicts LB1 far outside the range of Southeast Asian and African pygmies in both absolute height and body mass indices. "Attempts to dismiss the hobbits as pathological people have failed repeatedly because the medical diagnoses of dwarfing syndromes and microcephaly bear no resemblance to the unique anatomy of Homo floresiensis," noted Dr. Baab.

"The geometry of hobbits: Homo floresiensis and human evolution." William Jungers and Karen Baab. Significance; Published Online: November 19, 2009

Sunday, 25 October 2009

The feet of Homo floresiensis were primitive but not pathological

A detailed analysis of the feet of Homo floresiensis—the miniature hominins who lived on a remote island in eastern Indonesia until 18,000 years ago—may help settle a question hotly debated among paleontologists: how similar was this population to modern humans? A new research paper, featured on the cover of the current issue of Nature, may answer this question. While the so-called "hobbits" walked on two legs, several features of their feet were so primitive that their gait was not efficient.

"The hobbits were bipedal, but they walked in a different way from modern humans," explains William Harcourt-Smith, a Research Scientist in the Division of Paleontology at the American Museum of Natural History and an author on the paper. "Their feet have a combination of human-like and more primitive early hominin traits, some of which are more akin to those in Lucy." Lucy is an early bipedal but small-brained hominin, or australopithecine, that lived in Africa 3.2 million years ago.

The "hobbits," excavated from Liang Bua Cave on the island of Flores, were first described in 2004. Known specimens range in age from 90,000 to 18,000 years old, making them contemporaneous with modern humans. This, in combination with the unusually small stature and brain size of H. floresiensis, led to considerable debate among researchers and in the press. Some consider the population a separate species, while others have assessed the fossils as pathological modern humans. But a number of recent analyses of the skull, face, and wrist have found many unusually primitive features among the "hobbits" that are more similar to chimpanzees and Australopithecus, suggesting that the Flores inhabitants represent a remnant population of early hominins.

The anatomy of the foot described in the new paper might finally answer the pathological modern vs. primitive population question. Although the foot is characteristic of a biped—being stiff and having no opposable big toe—many other traits fall outside of the range for modern humans. The H. floresiensis foot is very long in proportion to the lower limb and considerably more than half the length of the thighbone; modern human feet are relatively shorter at about half of the femur's length. The stubby big toe of the hobbits is another primitive, chimp-like trait. But the pivotal clue comes from the navicular bone, an important tarsal bone that helps form the arch in a modern human foot. The "hobbit" navicular bone is more akin to that found in great apes, which means that these hominins lacked an arch and were not efficient long-term runners.
"Arches are the hallmark of a modern human foot," explains Harcourt-Smith. "This is another strong piece of the evidence that the "hobbit" was not like us."

Researchers also assessed the pathology hypothesis by comparing "hobbit" feet to those of typical modern humans and pathological modern specimens such as pituitary dwarfs. While the pathological specimens fell well within the range of modern humans, the "hobbits" did not. This suggests that H. floresiensis was an unusual, isolated population of early hominins.

"The fossil record continues to surprise us," says William Jungers, Chairman of the Department of Anatomical Sciences at Stony Brook University Medical Center, and an author on the study. "H. floresiensis is either an island-dwarfed descendant of H. erectus that not only underwent body-size reduction but also extensive evolutionary reversals, or, as our analysis suggests, it represents a new species full of primitive retentions from an ancestor that dispersed out of Africa much earlier than anyone would have predicted. Either way, the implications for human evolution are profound."

Source:Eurekalert 09.

Friday, 23 October 2009

Charles Darwin: In His Footsteps

3 October 2009-30 August 2010
Free entry

See Charles Darwin's story unfold through larger than life illustrations in a graphic novel style alongside fantastic objects, some collected by Darwin himself.
See Darwin as you have never seen him before and discover the key moments in the development of his career, from his childhood interest in nature to his discovery of the most important idea in biology. Find out about the importance of Darwin's less well known work, from pigeon breeding to the origin of coral reefs on submarine volcanoes.
Explore the reaction to Darwin's ideas and their impact on science and society.
Discover how natural selection continues to create the diversity we see in the natural world- just what is a species and what is the evidence for evolution?
Find out about Manchester's links to Darwin's ideas - from the story of the Peppered Moth to the history of The Manchester Museum.

Experience extraordinary places and wildlife through the evocative words of Charles Darwin and breathtaking images from photographer Ben Hall.
"The glories of the vegetation of the Tropics rise before my mind at the present time more vividly than anything else. Though the sense of sublimity, which the great deserts of Patagonia and the forest-clad mountains of Tierra del Fuego excited in me, has left an indelible impression on my mind." (From Charles Darwin's autobiography, written in 1876, 40 years after the voyage of the Beagle)
"In many parts magnificent glaciers extended from the mountain side to the water's edge. It is scarcely possible to imagine any thing more beautiful than the beryl-like blue of the glacier, and especially when contrasted with the dead white of an expanse of snow. As fragments fell from the glacier into the water, they floated away, and the channel with its icebergs represented in miniature the polar sea." (The Voyage of the Beagle, p.245, January 1833 Tierra del Fuego)
Charles Darwin spent more time in South America than he did anywhere else when voyaging on HMS Beagle during 1831-36. Darwin's popular account of his experiences, usually called The Voyage of the Beagle, was published in 1845 and became an instant bestseller. This book has been one of the most popular travel narratives ever written. The book contains many evocative descriptions of the things Darwin saw.
Ben Hall is one of Britain's foremost wildlife photographers. His personal approach to wildlife photography lies in the creative art of 'seeing'. His aim is to use his pictures to communicate his personal vision, to generate an emotional response and to excite the viewer's aesthetic sensitivity. Ben often pre-visualises a particular image in his mind before setting out to photograph it. To realise this vision by turning it into a photographic image can take weeks or even months, and often sees him returning frequently to the same location to capture the perfect shot.
Find out more about Ben Hall at:
Read about Charles Darwin's time in South America here:
Read Charles Darwin's letters here:
Dinosaur evolution
Evolution of birds
Evolution of microbes
Molecular evolution

Bipedal Humans Came Down From The Trees, Not Up From The Ground

A detailed examination of the wrist bones of several primate species challenges the notion that humans evolved their two-legged upright walking style from a knuckle-walking ancestor.

The same lines of evidence also suggest that knuckle-walking evolved at least two different times, making gorillas distinct from chimpanzees and bonobos.
"We have the most robust data I've ever seen on this topic," said Daniel Schmitt, a Duke University associate professor of evolutionary anthropology. "This model should cause everyone to re-evaluate what they've said before."
A report on the findings will appear online during the week of Aug. 10 in the research journal Proceedings of the National Academy of Sciences.
The research, led by post-doctoral research associate Tracy Kivell, was supported by the Natural Sciences and Engineering Research Council in her native Canada, General Motors' Women in Science and Mathematics, and the University of Toronto, where Kivell did her Ph.D. work.
The debate over the origins of human bipedalism began during Charles Darwin's lifetime and continues vigorously to this day, commonly dividing into two competing models, the researchers explained.
One model "envisions the pre-human ancestor as a terrestrial knuckle-walker, a behavior frequently used by our closest living relatives, the African apes," they wrote in the PNAS report. The other model traces our two-legged walking to earlier tree-climbing, a mode of locomotion that is used by all living apes.
Supporters of the knuckle-walking origin think we and African apes evolved from a common knuckle walking ancestor. That connection, they contend, is still evident in wrist and hand bone features shared by African apes and by fossil and living humans.
But Kivell found otherwise when she began comparing juvenile and adult wrist bones of more than 100 chimps and bonobos, our closest living primate kin, with those of gorillas.
Significantly, two key features associated with knuckle walking were present in only 6 percent of the gorilla specimens she studied. But she found them in 96 percent of adult chimpanzees and 76 percent of bonobos. In all, she looked at specimens from 91 gorillas, 104 chimps and 43 bonobos.
Kivell and Schmitt suggested that one explanation for the absence of these features in gorillas is that they knuckle-walk in a fundamentally different way from chimps and bonobos. Gorillas stride with their arms and wrists extended straight down and locked in what Kivell called "columnar" stances that resemble how elephants walk. By contrast, chimps and bonobos walk more flexibly, "with their wrists in a bent position as opposed to being stacked-up," she said. "And with their wrists in bent positions there will be more stresses at those joints."
As a result, chimp and bonobo wrists have special features that gorillas lack -- little ridges and concavities that serve as "bony stops" to keep their wrists from over-bending. Gorillas don't need those, she added.
"When we first got together to work on this study that (difference) really jumped out in living color," Schmitt said.
"Then we sat down together and asked: 'What are the differences between them?' Schmitt said. "The answer is that chimps and bonobos spend a lot of time in the trees. And gorillas do not."
Chimpanzees and bonobos have a more extended-wrist way of knuckle-walking which gives them added stability on branches, the researchers concluded. In contrast, gorillas' "columnar" style of knuckle-walking is consistent with ground transport.
Indeed, "from what we know about knuckle-walking among wild populations, gorillas and adult chimpanzees will both knuckle-walk about 85 percent of the time that they're moving," Kivell said. "But chimpanzees and bonobos are more arboreal than gorillas. So they're doing a lot more of it in the trees."
Kivell and Schmitt think this suggests independent evolution of knuckle-walking behavior in the two African ape lineages.
Some scientists point to features in the human anatomy as our own vestiges of a knuckle-walking ancestry. One notable example is the fusion a two wrist bones that could provide us extra stability, a feature we share with gorillas, chimps and bonobos.
But some lemurs have that feature too, and they do a variety of different movements in the trees but do not knuckle-walk, Kivell said.
Altogether, the evidence leans against the idea that our own bipedalism evolved from a knuckle-walking ancestor, the pair wrote. "Instead, our data support the opposite notion, that features of the hand and wrist found in the human fossil record that have traditionally been treated as indicators of knuckle-walking behavior in general are in fact evidence of arboreality."
In other words, a long-ago ancestor species that spent its time in the trees moved to the ground and began walking upright.
There are no fossils from the time of this transition, which likely occurred about seven million years ago, Kivell and Schmitt said. But none of the later fossils considered to be on the direct human line were knuckle-walkers.

Source:Eurekalert 2009/10

Wednesday, 21 October 2009

"Ida" 47 million year old primate.

The article, entitled, Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology, documents the discovery of a remarkably complete and well-preserved fossil of an extinct early primate in Messel Pit, Germany, a site of great significance for fossils of the Eocene epoch.

The creature, named Darwinius masillae by the paper’s authors, lived an estimated 47 million years ago and is the first example of a previously unknown genus of primate. The fossil, known as “Ida,” is 95% complete and includes the skeleton, an outline of the creature’s body and the contents of her gut, allowing the researchers to reconstruct her life history and diet. Ida was an agile, young, herbivorous, female, about the size of a small monkey, who feasted on fruit and leaves in the trees of the Messel rain forest and died, aged about nine months, at the edge of a volcanic lake.

Although Darwinius masillae shares some characteristics with prosimians, such as the lemur, X-rays of the fossil crucially reveal the lack of a “toothcomb” and a “grooming claw,” an attribute of lemurs. Meanwhile, the fossil’s opposable big toes and nail-bearing fingers and toes confirm it to be a primate, and a foot bone called the talus bone links Ida directly to humans. Ida thus provides the most complete understanding of the paleobiology of any Eocene primate so far discovered.

“This fossil is so complete,” said Dr Hurum. “Everything’s there. It’s unheard of in the primate record at all. You have to get to human burial to see something that’s this complete.”

Thursday, 15 October 2009

Ardi's feet, pelvis, legs, and hands suggest she was a biped on the ground but a quadruped when moving about in the trees

Picture courtesy J. H. Matternes via Science/AAAS
Scientists today announced the discovery of the oldest fossil skeleton of a human ancestor. The find reveals that our forebears underwent a previously unknown stage of evolution more than a million years before Lucy, the iconic early human ancestor specimen that walked the Earth 3.2 million years ago.
The centerpiece of a treasure trove of new fossils, the skeleton—assigned to a species called Ardipithecus ramidus—belonged to a small-brained, 110-pound (50-kilogram) female nicknamed "Ardi." (See pictures of Ardipithecus ramidus.)
The fossil puts to rest the notion, popular since Darwin's time, that a chimpanzee-like missing link—resembling something between humans and today's apes—would eventually be found at the root of the human family tree. Indeed, the new evidence suggests that the study of chimpanzee anatomy and behavior—long used to infer the nature of the earliest human ancestors—is largely irrelevant to understanding our beginnings.
(Interactive time line: how the Ardipithecus ramidus discovery changes human evolutionary theory.)
Ardi instead shows an unexpected mix of advanced characteristics and of primitive traits seen in much older apes that were unlike chimps or gorillas (interactive: Ardi's key features). As such, the skeleton offers a window on what the last common ancestor of humans and living apes might have been like.
The analysis of the Ardipithecus ramidus bones will be published in a collection of papers tomorrow in a special edition of the journal Science, along with an avalanche of supporting materials published online.
"This find is far more important than Lucy," said Alan Walker, a paleontologist from Pennsylvania State University who was not part of the research. "It shows that the last common ancestor with chimps didn't look like a chimp, or a human, or some funny thing in between."

Ardi Surrounded by Family
The Ardipithecus ramidus fossils were discovered in Ethiopia's harsh Afar desert at a site called Aramis in the Middle Awash region, just 46 miles (74 kilometers) from where Lucy's species, Australopithecus afarensis, was found in 1974. Radiometric dating of two layers of volcanic ash that tightly sandwiched the fossil deposits revealed that Ardi lived 4.4 million years ago.
Older hominid fossils have been uncovered, including a skull from Chad  at least six million years old and some more fragmentary, slightly younger remains from Kenya and nearby in the Middle Awash.
While important, however, none of those earlier fossils are nearly as revealing as the newly announced remains, which in addition to Ardi's partial skeleton include bones representing at least 36 other individuals.
"All of a sudden you've got fingers and toes and arms and legs and heads and teeth," said Tim White of the University of California, Berkeley, who co-directed the work with Berhane Asfaw, a paleoanthropologist and former director of the National Museum of Ethiopia, and Giday WoldeGabriel, a geologist at Los Alamos National Laboratory in New Mexico.
"That allows you to do something you can't do with isolated specimens," White said. "It allows you to do biology."

Ardi's Weird Way of Moving
The biggest surprise about Ardipithecus's biology is its bizarre means of moving about.
All previously known hominids—members of our ancestral lineage—walked upright on two legs, like us. But Ardi's feet, pelvis, legs, and hands suggest she was a biped on the ground but a quadruped when moving about in the trees.
Her big toe, for instance, splays out from her foot like an ape's, the better to grasp tree limbs. Unlike a chimpanzee foot, however, Ardipithecus's contains a special small bone inside a tendon, passed down from more primitive ancestors, that keeps the divergent toe more rigid. Combined with modifications to the other toes, the bone would have helped Ardi walk bipedally on the ground, though less efficiently than later hominids like Lucy. The bone was lost in the lineages of chimps and gorillas.
According to the researchers, the pelvis shows a similar mosaic of traits. The large flaring bones of the upper pelvis were positioned so that Ardi could walk on two legs without lurching from side to side like a chimp. But the lower pelvis was built like an ape's, to accommodate huge hind limb muscles used in climbing.
Even in the trees, Ardi was nothing like a modern ape, the researchers say.
Modern chimps and gorillas have evolved limb anatomy specialized to climbing vertically up tree trunks, hanging and swinging from branches, and knuckle-walking on the ground.
While these behaviors require very rigid wrist bones, for instance, the wrists and finger joints of Ardipithecus were highly flexible. As a result Ardi would have walked on her palms as she moved about in the trees—more like some primitive fossil apes than like chimps and gorillas.
"What Ardi tells us is there was this vast intermediate stage in our evolution that nobody knew about," said Owen Lovejoy, an anatomist at Kent State University in Ohio, who analyzed Ardi's bones below the neck. "It changes everything."
Against All Odds, Ardi Emerges
The first, fragmentary specimens of Ardipithecus were found at Aramis in 1992 and published in 1994. The skeleton announced today was discovered that same year and excavated with the bones of the other individuals over the next three field seasons. But it took 15 years before the research team could fully analyze and publish the skeleton, because the fossils were in such bad shape.
After Ardi died, her remains apparently were trampled down into mud by hippos and other passing herbivores. Millions of years later, erosion brought the badly crushed and distorted bones back to the surface.
They were so fragile they would turn to dust at a touch. To save the precious fragments, White and colleagues removed the fossils along with their surrounding rock. Then, in a lab in Addis, the researchers carefully tweaked out the bones from the rocky matrix using a needle under a microscope, proceeding "millimeter by submillimeter," as the team puts it in Science. This process alone took several years.
Pieces of the crushed skull were then CT-scanned and digitally fit back together by Gen Suwa, a paleoanthropologist at the University of Tokyo.
In the end, the research team recovered more than 125 pieces of the skeleton, including much of the feet and virtually all of the hands—an extreme rarity among hominid fossils of any age, let alone one so very ancient.
"Finding this skeleton was more than luck," said White. "It was against all odds."
Ardi's World
The team also found some 6,000 animal fossils and other specimens that offer a picture of the world Ardi inhabited: a moist woodland very different from the region's current, parched landscape. In addition to antelope and monkey species associated with forests, the deposits contained forest-dwelling birds and seeds from fig and palm trees.
Wear patterns and isotopes in the hominid teeth suggest a diet that included fruits, nuts, and other forest foods.
If White and his team are right that Ardi walked upright as well as climbed trees, the environmental evidence would seem to strike the death knell for the "savanna hypothesis"—a long-standing notion that our ancestors first stood up in response to their move onto an open grassland environment.
Sex for Food
Some researchers, however, are unconvinced that Ardipithecus was quite so versatile.
"This is a fascinating skeleton, but based on what they present, the evidence for bipedality is limited at best," said William Jungers, an anatomist at Stony Brook University in New York State.
"Divergent big toes are associated with grasping, and this has one of the most divergent big toes you can imagine," Jungers said. "Why would an animal fully adapted to support its weight on its forelimbs in the trees elect to walk bipedally on the ground?"
One provocative answer to that question—originally proposed by Lovejoy in the early 1980s and refined now in light of the Ardipithecus discoveries—attributes the origin of bipedality to another trademark of humankind: monogamous sex.
Virtually all apes and monkeys, especially males, have long upper canine teeth—formidable weapons in fights for mating opportunities.
But Ardipithecus appears to have already embarked on a uniquely human evolutionary path, with canines reduced in size and dramatically "feminized" to a stubby, diamond shape, according to the researchers. Males and female specimens are also close to each other in body size.
Lovejoy sees these changes as part of an epochal shift in social behavior: Instead of fighting for access to females, a male Ardipithecus would supply a "targeted female" and her offspring with gathered foods and gain her sexual loyalty in return.
To keep up his end of the deal, a male needed to have his hands free to carry home the food. Bipedalism may have been a poor way for Ardipithecus to get around, but through its contribution to the "sex for food" contract, it would have been an excellent way to bear more offspring. And in evolution, of course, more offspring is the name of the game (more: "Did Early Humans Start Walking for Sex?").
Two hundred thousand years after Ardipithecus, another species called Australopithecus anamensis appeared in the region. By most accounts, that species soon evolved into Australopithecus afarensis, with a slightly larger brain and a full commitment to a bipedal way of life. Then came early Homo, with its even bigger brain and budding tool use.
Did primitive Ardipithecus undergo some accelerated change in the 200,000 years between it and Australopithecus—and emerge as the ancestor of all later hominids? Or was Ardipithecus a relict species, carrying its quaint mosaic of primitive and advanced traits with it into extinction?
Study co-leader White sees nothing about the skeleton "that would exclude it from ancestral status." But he said more fossils would be needed to fully resolve the issue.
Stony Brook's Jungers added, "These finds are incredibly important, and given the state of preservation of the bones, what they did was nothing short of heroic.
But this is just the beginning of the story."

Source:National Geographic 15/10/09

Saturday, 12 September 2009

Archaeologists discover oldest-known fiber materials used by early humans Flax fibers could have been used for warmth and mobility; for rope, shoes ,

(The microscopic samples were found in the Dzudzuana Cave in Georgia)

A team of archaeologists and paleobiologists has discovered flax fibres that are more than 34,000 years old, making them the oldest fibres known to have been used by humans. The fibers, discovered during systematic excavations in a cave in the Republic of Georgia, are described in this week's issue of Science.

The flax, which would have been collected from the wild and not farmed, could have been used to make linen and thread, the researchers say. The cloth and thread would then have been used to fashion garments for warmth, sew leather pieces, make cloths, or tie together packs that might have aided the mobility of our ancient ancestors from one camp to another.

The excavation was jointly led by Ofer Bar-Yosef, George Grant MacCurdy and Janet G. B. MacCurdy Professor of Prehistoric Archaeology in the Faculty of Arts and Sciences at Harvard University, with Tengiz Meshveliani from the Georgian State Museum and Anna Belfer-Cohen from the Hebrew University. The microscopic research of the soil samples in which numerous flax fibers were discovered was done by Eliso Kvavadze of the Institute of Paleobiology, part of the National Museum of Georgia.

"This was a critical invention for early humans. They might have used this fibre to create parts of clothing, ropes, or baskets—for items that were mainly used for domestic activities," says Bar-Yosef. "We know that this is wild flax that grew in the vicinity of the cave and was exploited intensively or extensively by modern humans."

The items created with these fibres increased early humans chances of survival and mobility in the harsh conditions of this hilly region. The flax fibres could have been used to sew hides together for clothing and shoes, to create the warmth necessary to endure cold weather. They might have also been used to make packs for carrying essentials, which would have increased and eased mobility, offering a great advantage to a hunter-gatherer society.

Some of the fibres were twisted, indicating they were used to make ropes or strings. Others had been dyed. Early humans used the plants in the area to color the fabric or threads made from the flax.

Today, these fibres are not visible to the eye, because the garments and items sewed together with the flax have long ago disintegrated. Bar-Yosef, Kvavadze and colleagues discovered the fibres by examining samples of clay retrieved from different layers of the cave under a microscope.

The discovery of such ancient fibres was a surprise to the scientists. Previously, the oldest known were imprints of fibers in small clay objects found in Dolni Vestonice, a famous site in the Czech Republic some 28,000 years old.

The scientists' original goal was to analyze tree pollen samples found inside the cave, part of a study of environmental and temperature fluctuations over the course of thousands of years that would have affected the lives of these early humans. However, while looking for this pollen, Kvavadze, who led the analysis of the pollen, also discovered non-pollen polymorphs – these flax fibres.

Bar-Yosef and his team used radiocarbon dating to date the layers of the cave as they dug the site, revealing the age of the clay samples in which the fibers were found. Flax fibres were also found in the layers that dated to about 21,000 and 13,000 years ago.

Bar-Yosef's team began the excavations of this cave in 1996, and has returned to the site each year to complete this work.

"We were looking to find when the cave was occupied, what was the nature of the occupation by those early hunter-gatherers, where did they go hunting and gathering food, what kind of stone tools they used, what types of bone and antler tools they made and how they used them, whether they made beads and pendants for body decoration, and so on," says Bar-Yosef. "This was a wonderful surprise, to discover these ancient flax fibres at the end of this excavation project."

Eurekalert 12/09/09

Wednesday, 17 June 2009

Researchers gain genome-wide insights into patterns of the world's human population structures

Deep mining of data offers information on human evolution and relationships among populations.

Through sophisticated statistical analyses and advanced computer simulations, researchers are learning more about the genomic patterns of human population structure around the world.

Revealing such patterns provides insights into the history of human evolution, the predominant evolutionary forces that shaped local populations, and the relationships among populations.

"Studying genomic patterns of human population structure also has practical applications in disease-gene mapping," noted Dr. Joshua M. Akey, University of Washington (UW) assistant professor of genome sciences. Akey is senior author of new genomic research findings about the fine-scale structure of diverse human populations. The results will be published May 15 in the American Journal of Human Genetics. The lead authors were Shameek Biswas and Dr. Laura B. Scheinfeldt, both of the UW Department of Genome Sciences.

A statistical method called principle component analysis allows researchers to look through a thick, voluminous fog of genetic data and see significant variations. The UW researchers applied this method to a data set of almost 650,000 SNPs (pronounced "snips").

A single nucleotide polymorphism is a genetic variation in which the DNA code differs by only one "letter" in the same DNA sequence from two individuals of the same species. The data set of 650,000 SNPs came from 944 unrelated persons representing 52 broadly classified populations living in several regions on seven continental groups: Africa, America, Central and South East Asia, East Asia, Europe, Middle East, and Oceania. This global sampling came from The Human Genome Diversity Project - Center for the Study of Human Polymorphisms

Most previous genomic studies of this nature have focused on broad-scale patterns of structure among geographically diverse populations, the UW researchers noted. These studies concluded that 85 to 95 percent of human genetic variation can be attributed to differences among individuals, and 5 to 15 percent is due to differences between populations.

In contrast to these broad-scale patterns, more recently researchers have tried to look at fine-scale population structure. Usually these studies focus on only the two or three top- ranking axes of genetic variation emerging from the statistical analysis. For example, studies of European individuals have shown a strong correlation between the top two axes of genetic variation and the actual geographical location of the sampling.

In their newly published findings, UW researchers demonstrated that substantial information on population structure is hidden more deeply in the genomic data. They were able to identify 18 significant, informative axes of variation. Some of these distinguished particular populations.

The UW researchers also conservatively estimated the set of all of the SNPs, or specific, tiny DNA code differences, matching each of the most informative axes of variation. These variations represent numerous fixed positions on the human genome where different biomarkers can sit and thereby form a "genomic signature" of population structure. They also allow for more detailed inferences, the UW researchers noted, about the evolutionary forces that shape the fine-scaled patterns of human population structure.

"The genome-wide distribution of these markers," Akey believes, "can largely be accounted for by genetic drift." Genetic drift is gradual accumulation of random changes in the gene pool of small populations. Akey added that some of these variations, however, do cluster in regions of the human genome considered to be targets of recent adaptive evolution.

The researchers also observed patterns of human genetic variation that correlated with geography in essentially every continental group. While such geographical patterns have been described in European samples, the researchers think that the extent to which such geographic correlations might be found in other continents may not be fully appreciated.

In mentioning the limitations of his study approach, Akey cautioned that there are still questions about the best way to design human population genetics research in terms of sampling individuals and populations, but that progress is likely.

"Now that we have increasingly dense catalogs of genetic variation," Akey wrote, "the details of human population structure are becoming more tractable. The testing of increasingly refined hypotheses about human population structure should yield new insights into the history and relationships among human genomes."

Eurekalert 2009.

High population density triggers cultural explosions

Increasing population density, rather than boosts in human brain power, appears to have catalysed the emergence of modern human behaviour, according to a new study by UCL (University College London) scientists published in the journal Science. High population density leads to greater exchange of ideas and skills and prevents the loss of new innovations. It is this skill maintenance, combined with a greater probability of useful innovations, that led to modern human behaviour appearing at different times in different parts of the world.

In the study, the UCL team found that complex skills learnt across generations can only be maintained when there is a critical level of interaction between people. Using computer simulations of social learning, they showed that high and low-skilled groups could coexist over long periods of time and that the degree of skill they maintained depended on local population density or the degree of migration between them. Using genetic estimates of population size in the past, the team went on to show that density was similar in sub-Saharan Africa, Europe and the Middle-East when modern behaviour first appeared in each of these regions. The paper also points to evidence that population density would have dropped for climatic reasons at the time when modern human behaviour temporarily disappeared in sub-Saharan Africa.

Adam Powell, AHRC Centre for the Evolution of Cultural Diversity, says: "Our paper proposes a new model for why modern human behaviour started at different times in different regions of the world, why it disappeared in some places before coming back, and why in all cases it occurred more than 100,000 years after modern humans first appeared.

"By modern human behaviour, we mean a radical jump in technological and cultural complexity, which makes our species unique. This includes symbolic behavior, such as abstract and realistic art, and body decoration using threaded shell beads, ochre or tattoo kits; musical instruments; bone, antler and ivory artefacts; stone blades; and more sophisticated hunting and trapping technology, like bows, boomerangs and nets.

Professor Stephen Shennan, UCL Institute of Archaeology, says: "Modern humans have been around for at least 160,000 to 200,000 years but there is no archaeological evidence of any technology beyond basic stone tools until around 90,000 years ago. In Europe and western Asia this advanced technology and behaviour explodes around 45,000 years ago when humans arrive there, but doesn't appear in eastern and southern Asia and Australia until much later, despite a human presence. In sub-Saharan Africa the situation is more complex. Many of the features of modern human behaviour – including the first abstract art – are found some 90,000 years ago but then seem to disappear around 65,000 years ago, before re-emerging some 40,000 years ago.

"Scientists have offered many suggestions as to why these cultural explosions occurred where and when they did, including new mutations leading to better brains, advances in language, and expansions into new environments that required new technologies to survive. The problem is that none of these explanations can fully account for the appearance of modern human behaviour at different times in different places, or its temporary disappearance in sub-Saharan Africa."

Dr Mark Thomas, UCL Genetics, Evolution and Environment, says: "When we think of how we came to be the sophisticated creatures we are, we often imagine some sudden critical change, a bit like when the black monolith appears in the film 2001: A Space Odyssey. In reality, there is no evidence of a big change in our biological makeup when we started behaving in an intelligent way. Our model can explain this even if our mental capacities are the same today as they were when we first originated as a species some 200,000 years ago.

"Ironically, our finding that successful innovation depends less on how smart you are than how connected you are seems as relevant today as it was 90,000 years ago.

Eurekalert 17/06/09

New 'molecular clock' aids dating of human migration history

Researchers at the University of Leeds have devised a more accurate method of dating ancient human migration – even when no corroborating archaeological evidence exists.

Estimating the chronology of population migrations throughout mankind's early history has always been problematic. The most widely used genetic method works back to find the last common ancestor of any particular set of lineages using samples of mitochondrial DNA (mtDNA), but this method has recently been shown to be unreliable, throwing 20 years of research into doubt.

The new method refines the mtDNA calculation by taking into account the process of natural selection - which researchers realised was skewing their results - and has been tested successfully against known colonisation dates confirmed by archaeological evidence, such as in Polynesia in the Pacific (approximately 3,000 years ago), and the Canary Islands (approximately 2,500 years ago).

Says PhD student Pedro Soares who devised the new method: "Natural selection's very gradual removal of harmful gene mutations in the mtDNA produces a time-dependent effect on how many mutations you see in the family tree. What we've done is work out a formula that corrects this effect so that we now have a reliable way of dating genetic lineages.

"This means that we can put a timescale on any part of the particular family tree, right back to humanity's last common maternal ancestor, known as 'Mitochondrial Eve', who lived some 200,000 years ago. In fact we can date any migration for which we have available data," he says.

Moreover, working with a published database of more than 2,000 fully sequenced mtDNA samples, Soares' calculation, for the first time, uses data from the whole of the mtDNA molecule. This means that the results are not only more accurate, but also more precise, giving narrower date ranges.

The new method has already yielded some surprising findings. Says archaogeneticist Professor Martin Richards, who supervised Soares: "We can settle the debate regarding mankind's expansion through the Americas. Researchers have been estimating dates from mtDNA that are too old for the archaeological evidence, but our calculations confirm the date to be some 15,000 years ago, around the time of the first unequivocal archaeological remains.

"Furthermore, we can say with some confidence that the estimate of humanity's 'out of Africa' migration was around 60-70,000 years ago – some 10-20,000 years earlier than previously thought."

The team has devised a simple calculator into which researchers can feed their data and this is being made freely available on the University of Leeds website.

Eurekalert 17/06/09

Monday, 6 April 2009

Archaeological discovery in Jordan valley: Enormous 'foot-shaped' enclosures

'The 'foot' structures that we found in the Jordan valley are the first sites that the People of Israel built upon entering Canaan and they testify to the biblical concept of ownership of the land with the foot'.

"The 'foot' structures that we found in the Jordan valley are the first sites that the People of Israel built upon entering Canaan and they testify to the biblical concept of ownership of the land with the foot," said archaeologist Prof. Adam Zertal of the University of Haifa, who headed the excavating team that exposed five compounds in the shape of an enormous "foot", that it were likely to have been used at that time to mark ownership of territory.
On the eve of the Passover holiday, researchers from the University of Haifa reveal an exceptional and exciting archaeological discovery that dates back to the time of the People of Israel's settlement in the country: For the first time, enclosed sites identified with the biblical sites termed in Hebrew "gilgal", which were used for assemblies, preparation for battle, and rituals, have been revealed in the Jordan valley. The researchers, headed by Prof. Adam Zertal, exposed five such structures, each in the shape of an enormous "foot", which they suppose functioned during that period to mark ownership on the territory. "I am an archaeologist and only deal with the scientific findings, so I do not go into the additional meanings of the discovery, if there are any," Prof. Zertal said.
The Hebrew word "gilgal" (a camp or stone-structure), is mentioned thirty-nine times in the Bible. The stone enclosures were located in the Jordan valley and the hill country west of it. To this day, no archaeological site has been proposed to be identified with the gilgal. Between the years 1990 and 2008, during the Manasseh Hill-Country Survey that covers Samaria and the Jordan Valley, five such enclosures were found and excavated, all designed in the shape of a human foot. All of these sites were established at the outset of the Iron Age I (the 13th-12th centuries BCE). Based on their size and shape, it is clear that they were used for human assembly and not for animals.
Two of the sites (in Bedhat esh-Sha'ab and Yafit 3) were excavated in the years 2002-2005, under the directorship of Dr. Ben-Yosef and the guidance of Adam Zertal. The findings, mostly of clay vessels and animal bones, date their foundation to the end of the 13th century BCE, and one of them endured up to the 9th or 8th century BCE without architectonic adjustment.
In at least two cases, paved circuits, some two meters wide, were found around the structures. These were probably used to encircle the sites in a ceremony. "Ceremonial encirclement of an area in procession is an important element in the ancient Near East," Prof. Zertal says, adding that the origins of the Hebrew term "hag" (festival) in Semitic languages is from the verb "hug", which means "encircle". Thus, this discovery can also shed new light on the religious processions and the meaning of the Hebrew word for festival, "hag".
Prof. Zertal emphasized that the "foot" held much significance as a symbol of ownership of territory, control over an enemy, connection between people and land, and presence of the Deity. Some of these concepts are mentioned in ancient Egyptian literature. The Bible also has a wealth of references to the importance of the "foot" as a symbol: of ownership over Canaan, the bond between the People of Israel and their land, the link between the People and God's promise to inherit the land, defeating the enemy 'underfoot', and the Temple imaged as a foot.
"The discovery of these 'foot' structures opens an entirely new system of linguistic and historical perceptions," Prof. Zertal emphasizes. He explains that the meaning of the biblical Hebrew word for "foot" - "regel" – is also a "festival", "holiday", and ascending to see the face of God. As such, the source of the Hebrew term "aliya la-regel", literally translated as "ascending to the foot" (and now known in English as a pilgrimage), is attributed to the "foot" sites in the Jordan valley. "Now, following these discoveries, the meanings of the terms become clear. Identifying the 'foot' enclosures as ancient Israeli ceremonial sites leads us to a series of new possibilities to explain the beginnings of Israel, of the People of Israel's festivals and holidays," he stated.
According to Prof. Zertal, the "foot" constructions were used for ceremonial assemblies during Iron Age I (and probably after). When the religious center was moved to Jerusalem and settled there, the command of "aliya la-regel" (pilgrimage) became associated with Jerusalem. The source of the term, however, is in the sites that have now been discovered in the Jordan valley and the Altar on Mt. Ebal. "The biblical text testifies to the antiquity of these compounds in Israel's ceremonials, and the 'foot' structures were built by an organized community that had a central leadership," Prof. Zertal stated. He stressed that there is a direct connection between the biblical ideology, which identifies ownership over the new land with the foot and hence with the shape of the constructions.

Source:Eurekalert 6th April 2009.

Saturday, 28 February 2009

1.5 million-year-old fossil humans walked on modern feet

Image courtesy Matthew Bennett, Bournemouth University

Footprints found at Ileret, Kenya, display anatomically modern features.

Ancient footprints found at Rutgers' Koobi Fora Field School show that some of the earliest humans walked like us and did so on anatomically modern feet 1.5 million years ago.
Published as the cover story in the Feb. 27 issue of the journal Science, this anatomical interpretation is the conclusion of Rutgers Professor John W.K. Harris and an international team of colleagues. Harris is a professor of anthropology at Rutgers, The State University of New Jersey, member of the Center for Human Evolutionary Studies and director of the Koobi Fora Field Project.
Harris is also director of the field school which Rutgers University operates in collaboration with the National Museums of Kenya. From 2006 to 2008, the field school group of mostly American undergraduates, including Rutgers students, excavated the site yielding the footprints.
The footprints were discovered in two 1.5 million-year-old sedimentary layers near Ileret in northern Kenya. These rarest of impressions yielded information about soft tissue form and structure not normally accessible in fossilized bones. The Ileret footprints constitute the oldest evidence of an essentially modern human-like foot anatomy.
To ensure that comparisons made with modern human and other fossil hominid footprints were objective, the Ileret footprints were scanned and digitized by the lead author, Professor Matthew Bennett of Bournemouth University in the United Kingdom.
The authors of the Science paper reported that the upper sediment layer contained three footprint trails: two trails of two prints each, one of seven prints and a number of isolated prints. Five meters deeper, the other sediment surface preserved one trail of two prints and a single isolated smaller print, probably from a juvenile.
In these specimens, the big toe is parallel to the other toes, unlike that of apes where it is separated in a grasping configuration useful in the trees. The footprints show a pronounced human-like arch and short toes, typically associated with an upright bipedal stance. The size, spacing and depth of the impressions were the basis of estimates of weight, stride and gait, all found to be within the range of modern humans.
Based on size of the footprints and their modern anatomical characteristics, the authors attribute the prints to the hominid Homo ergaster, or early Homo erectus as it is more generally known. This was the first hominid to have had the same body proportions (longer legs and shorter arms) as modern Homo sapiens. Various H. ergaster or H. erectus remains have been found in Tanzania, Ethiopia, Kenya and South Africa, with dates consistent with the Ileret footprints.
Other hominid fossil footprints dating to 3.6 million years ago had been discovered in 1978 by Mary Leakey at Laetoli, Tanzania. These are attributed to the less advanced Australopithecus afarensis, a possible ancestral hominid. The smaller, older Laetoli prints show indications of upright bipedal posture but possess a shallower arch and a more ape-like, divergent big toe.

Source: Eurekalert 28/02/09

Monday, 23 February 2009

Arsenic and old toenails

Scientists from Leicester and Nottingham have devised a method for identifying levels of exposure to environmental arsenic – by testing toenail clippings.

Arsenic occurs naturally in the environment and people can be exposed to it in several ways, for example through contaminated water, food, dust or soil. The risk of exposure is greater in certain areas of the UK where the natural geology and historic mining activities have led to widespread contamination of the environment with arsenic. Long term exposure to arsenic is associated with increases in lung, liver, bladder and kidney cancers and skin growths.

Previous studies using hair have suggested high levels of arsenic in the bodies of King George III and Napoleon Bonaparte. Now doctoral research at the British Geological Survey by Mark Button of the University of Leicester has used toenail clippings to find fresh evidence of exposure to environmental arsenic within a UK population living close to a former arsenic mine. The research, published online ahead of print in the Journal of Environmental Monitoring, was carried out with Dr Gawen Jenkin, Department of Geology, University of Leicester; Dr Chris Harrington, School of Science and Technology at Nottingham Trent University and Dr Michael Watts of the British Geological Survey. The research was funded by the British Geological Survey.

Mark Button said "We initially identified high levels of arsenic in earthworms living in contaminated soils surrounding the former mine. That got us thinking about potential exposure in people living close to the site."

The researchers collected toenails and washed and acid digested the samples under microwave irradiation. They then analysed the samples using inductively coupled plasma mass spectrometry.

Mark Button added: "This preliminary research indicates that people living close to a former arsenic mine have elevated levels of arsenic in their toenails. However, the potential health risks in this case, if any, are not yet clear and no arsenic related health issues have been reported. A large-scale and more detailed biomonitoring study is required to confirm these initial results."

Dr Jenkin, lecturer in Applied Geology at the University of Leicester said: "This is the first time that the chemical form of the arsenic in the toenails has been measured – that can tell us something about how it got in there and possible risk factors.

Dr Jenkin added: "There is definitely more research needed to look at - amongst other things - a larger sample of volunteers, to see if the values change with time (it is quite possible the high values recorded are a one-off for that person, or due to slow toenail growth concentrating harmless quantities of arsenic), and to look at the possible pathways by which the arsenic is ingested. Coupling our analyses with regular blood measurements would be very revealing."

However the researchers are definitely NOT requiring people to send in their toenail clippings. Neither can you assess arsenic contamination simply by looking at your toenails.

Dr Jenkin said: "Even in those people with elevated amounts it is present in tiny quantities – less than 0.003% in the toenail. In people who have not been exposed at all it is less than 0.00003%. If a nail looks different from normal that is usually due to physical damage (you stubbed your toe or dropped something on it) or a minor fungal infection that can be easily cleared up by a visit to the podiatrist."

Source: Eurekalert 23/02/09

Sunday, 22 February 2009

Bipedality and Childbirth.

Contrary to the TV sitcom where the wife experiencing strong labor pains screams at her husband to stay away from her, women rarely give birth alone. There are typically doctors, nurses and husbands in hospital delivery rooms, and sometimes even other relatives and friends. Midwives often are called on to help with births at home.

Assisted birth has likely been around for millennia, possibly dating as far back as 5million years ago when our ancestors first began walking upright, according to University of Delaware paleoanthropologist Karen Rosenberg.
She says that social assistance during childbirth is just one aspect of our evolutionary heritage that makes us distinctive as humans.
Rosenberg, who is a professor and chairperson of the Department of Anthropology at the University of Delaware, presented a talk on natural selection and childbirth on Feb. 13 at the annual meeting of the American Association for the Advancement of Science in Chicago. It was part of the symposium “The Invisible Woman in Evolution: Natural Cycle and Life-Cycle Events,” which Rosenberg co-organized.
The meeting's theme, “Our Planet and Its Life: Origins and Futures,” commemorated the 200th anniversary of Charles Darwin's birth and the 150th anniversary of the publication of his book On the Origin of Species by Means of Natural Selection.
“Humans need helpers in childbirth because it is difficult and potentially dangerous,” Rosenberg says. “While it's not so risky today -- maternal mortality is low -- as recently as two generations ago, it was not uncommon to hear of women dying in childbirth.”
Through fossil records and comparisons of humans with other primates, Rosenberg says that anthropologists can now show how the uniquely human traits of bipedalism, large brains, infant helplessness and social assistance all came together, resulting in the challenging and somewhat dangerous manner in which humans give birth.
When our ancestors evolved to begin walking on two legs, Rosenberg says, this upright posture created a wide but short opening in the pelvis in which the baby must travel, requiring a new form of birth so that the baby could find its way through a now tight birth canal.
According to Rosenberg, the average pelvic opening in women today is 13 centimeters at its largest diameter and 10 centimeters at its smallest. The average infant head is 10 centimeters from front to back, and the shoulders are 12 centimeters across. And today the birth canal is a twisty tunnel subjecting the infant to a series of complex twists and turns on its way out.
“Until recently, there was a sexism in the study of evolution,” Rosenberg says. “Researchers focused on men and the tools they used in hunting, and these things were more difficult to connect to reproductive success and hence to natural selection,” she notes.
“With childbirth, as well as many of the other things that happen to women -- pregnancy, nursing, menopause -- it's really easy to see how natural selection works,” Rosenberg notes.
Childbirth is just one of a series of examples throughout a woman's life cycle, in which enlisting the help of other women significantly improves reproductive outcomes, according to Rosenberg.
“Women take up the slack for other women when they are pregnant and nursing so that they have the energy to devote to their infants. Cooperative childcare is something in which women help each other out. Often, but not always, these helpers are post-reproductive women who have fewer of those responsibilities of their own, but may be helping out their daughters. All of this puts a great selective premium on a kind of social intelligence that many scientists think partly accounts for the increase in brain size that happened over the last two million years,” she notes.
How will women and childbirth continue to evolve? Will the birth canal grow narrower, or wider? Will childbirth become more painful, or easier? Will more helpers be needed in future births? It's really anybody's guess.
“Evolution doesn't have a direction,” Rosenberg says. “Knowing where we've been doesn't give us any help in where we're going. But it does help us understand what makes us human, as well as how we're connected to the natural world. ”
A graduate of the University of Chicago, Rosenberg received her doctorate in biological anthropology from the University of Michigan and joined the University of Delaware faculty in 1987.
She says she began focusing on the evolution of women and childbirth around the time she had her first child, although she doesn't think there was a connection between the two.
Ironically, her brother is an obstetrician although she and he have never conducted research together.

Source:Eurekalert 02/09
Article by Tracey Bryant. Photo by Ambre Alexander

Saturday, 14 February 2009

High-tech tests allow anthropologists to track ancient hominids across the landscape.

Caption: This is an an artist's representation of Paranthropus in southern Africa more than 1 million years ago.
Credit: Illustration courtesy of Walter Voigt/Lee Berger/Brett Hilton-Barber.

Dazzling new scientific techniques are allowing archaeologists to track the movements and menus of extinct hominids through the seasons and years as they ate their way across the African landscape, helping to illuminate the evolution of human diets.
Piecing together relationships between the diets of hominids several million years ago to that of early and modern humans is allowing scientists to see how diet relates to the evolution of cognitive abilities, social structures, locomotion and even disease, said University of Colorado at Boulder anthropology Professor Matt Sponheimer. Sponheimer organized a session titled "The Evolution of Human Diets" at the annual American Association for the Advancement of Science meeting Feb. 12-15 in Chicago.
Sponheimer specializes in stable isotope analysis, comparing particular forms of the same chemical element, like carbon, present in fossil remains to help reconstruct past lives of hominids. Zapping hominid teeth with lasers, for example, frees telltale carbon gases from the enamel, allowing scientists to pinpoint the types of plants consumed by the hominids and the environments where they lived, said Sponheimer, who also relies on the microscopic wear of ancient hominid teeth for data on food consumption.
"Darwin surmised more than 150 years ago in 'The Descent of Man' that changes in the subsistence or environment of human ancestors likely led to the advent of modern humans," Sponheimer said. "Dietary resources can be a force for evolution."
One hominid genus under study by Sponheimer is the 2 million-year-old Paranthropus, a short, upright member of the australopithecine family that includes the Ethiopian fossil, Lucy. Discovered in 1974, Lucy, believed to be roughly 3 million years old, is regarded by many anthropologists as the matriarch of modern humans.
A 2006 study by Sponheimer of Paranthropus robustus documented its diverse diet, clouding the notion that it was driven to extinction by its picky eating habits. And a 1999 study led by Sponheimer indicated 3-million-year-old australopithecines may have even have been catching and eating small animals.
"Paranthropus is sometimes referred to as a nutcracker because its flat teeth and powerful jaw muscles appear designed to eat hard foods," he said. "But some research suggests that the most mechanically challenging foods like nuts were eaten only at limited times of the year. "In addition, foods not previously considered to have been consumed in significant quantities, like sedges, grasses, seeds and perhaps even animal foods, were a significant part of the Paranthropus diet."
Roughly 2.5 million years ago, the australopithicenes are thought to have split into the genus Homo and the now-extinct genus Paranthropus, including South Africa's Paranthropus robustus and East Africa's Paranthropus boisei, said Sponheimer. Research presently under way at CU-Boulder indicates that while Paranthropus robustus and Paranthropus boisei are almost indistinguishable anatomically, they may have had very different diets.
Other intriguing research under way by Sponheimer and his colleagues hints that some female australopithecines, including members of the Paranthropus genus, died in different geographic areas than where they were born. The researchers are comparing such data to social patterns of chimpanzees, in which females generally migrate away from their original ranges and move into new areas -- the opposite of behavior charted in most other primates, said Sponheimer.
"Textbooks treat these ancient hominids as static piles of fossil bones," said Sponheimer. "We treat them as biological organisms moving across the landscape. It's entirely possible that many things we thought we knew about them were wrong, and pages of textbooks will have to have to be re-written."

Thursday, 8 January 2009

3 Diseases We May Be Able to Blame on Our Ancient Ancestors

The ADHD children of the world may have their wandering ancestors to blame. A genetic variant associated with impulsivity, novelty seeking, and attention deficit hyperactivity disorder (ADHD) might have actually been adaptive in nomadic populations, according to a a recent study by Dan Eisenberg at Northwestern University. Kenyan nomads with this variant, he says, may have been better at searching for food and defending their resources, giving them a survival advantage. But the study shows that the nomads’ settled descendants who carried this gene were more often malnourished than those without the gene. “Just because we don’t see a trait as being currently advantageous,” Eisenberg says, “does not preclude the trait from having had a function in the past.” Geneticists continue to unravel our ancestral evolution in hopes of better understanding how formerly advantageous genes have led to modern-day health problems.
High Blood PressureHigh blood pressure may be caused by a gene that was key to nomadic survival. The ability to retain salt—controlled in part by a gene called CYP3A5—varies by latitude, according to scientists at the University of Chicago. The closer a population lives to the equator, the better individuals are at retaining salt. “Since hunter-gatherers weren’t assured of getting sodium every day, they needed to be sure not to lose what they did acquire,” says Alan Weder, a hypertension specialist. But bring this gene to a modern setting—with couch lounging and salty snacking—and it is easy to retain more salt than is needed, which can lead to medical problems like high blood pressure.

3 Diseases We May Be Able to Blame on Our Ancient Ancestors
Obesity, lactose intolerance, and high blood pressure may all be traceable to hunter-gatherer survival. by Emily Anthes. Source: Discover Science,Technology and the Future.