Australopithecus sediba,a pivotal human ancestor

Fossils described last year as representatives of an ancient species critical to human evolution have reentered the scientific spotlight and set off a new round of debate over the finds’ true identity.
Researchers described analyses of new and previously recovered remains of a South African species called Australopithecus sediba on April 16 at a meeting of the American Association of Physical Anthropologists. Evidence is accumulating, they reported, that 2-million-year-old A. sediba formed an evolutionary connection between relatively apelike members of Australopithecus and the Homo genus, which includes living people.

A. sediba shares more skeletal features with early Homo specimens than any other known Australopithecus species.

According to  Darryl de Ruiter of Texas A&M University he states“We think A. sediba is a possible candidate ancestor for the genus Homo.” De Ruiter suspects that an isolated population of the hominid species Australopithecus africanus gradually evolved into A. sediba, resulting in a species characterized by an unusual mix of skeletal traits, some typical of Australopithecus in general and others of early Homo.

Ian Tattersall of the American Museum of Natural History endorsed A. sediba as a distinct species, probably closely related to A. africanus. he said“I wouldn’t classify it as the root of the Homo genus, though."

De Ruiter acknowledged the possibility that two partial A. sediba skeletons previously excavated from a collapsed, underground cave, as well as newly retrieved fossils from the cave, might represent a late-surviving form of Australopithecus africanus unrelated to Homo. Previous A. africanus finds date from about 3 million to 2.4 million years ago in South Africa. Fossils of A. africanus show lots of anatomical disparities from one individual to another, so that species might well encompass fossils attributed to A. sediba,said John Hawks of the University of Wisconsin. Much uncertainty surrounds the identity of fossil members of the human evolutionary family between 3 million and 2 million years ago.

Possible Homo fossils date to around 2.3 million years ago in East Africa, suggesting that even if A. sediba truly is a new species, it evolved after Homo did.

New A. sediba fossils from the same South African cave complex, many belonging to the previously discovered partial skeletons, underscore this ancient species’ mosaic anatomy, Berger said. A largely complete female pelvis displays relatively straight, vertically aligned hips and an elongated birth canal, much like early Homo species. Other Australopithecus females possessed a relatively short, wide pelvic opening and flaring hip bones.

New A. sediba foot bones include a chimplike heel and a humanlike ankle, Berger said. Fossils from the shoulders, rib cage and spine, as well as surprisingly long arm bones, typify Australopithecus.
Many newly recovered fossils are largely encased in hardened sediment. Computerized scanning produced 3-D images of complete fossils for analysis.

Digital reconstructions also aided an analysis led by De Ruiter of previously recovered A. sediba skulls and teeth, along with newly unearthed teeth. These remains also contain a blend of Australopithecus and Homo traits.

Adapted from article by  Bruce Bower

May 7th, 2011; Vol.179 #10 (p. 16)

Worlds oldest shoe

A perfectly preserved shoe, 1,000 years older than the Great Pyramid of Giza in Egypt and 400 years older than Stonehenge in the UK, has been found in a cave in Armenia.

The 5,500 year old shoe, the oldest leather shoe in the world, was discovered by a team of international archaeologists. 

The cow-hide shoe dates back to ~ 3,500 BC  (the Chalcolithic period) and is in perfect condition.  It was made of a single piece of leather and was shaped to fit the wearer’s foot.  It contained grass, although the archaeologists were uncertain as to whether this was to keep the foot warm or to maintain the shape of the shoe, a precursor to the modern shoe-tree perhaps?   “It is not known whether the shoe belonged to a man or woman,” said lead author of the research, Dr  Ron Pinhasi, University College Cork, Cork, Ireland   “as while small (European size 37; US size 7 women), the shoe could well have fitted a man from that era.”    The cave is situated in the Vayotz Dzor province of Armenia, on the Armenian, Iranian, Nakhichevanian and Turkish borders, and was known to regional archaeologists due to its visibility from the highway below.

The stable, cool and dry conditions in the cave resulted in exceptional preservation of the various objects that were found, which included large containers, many of which held well-preserved wheat and barley, apricots and other edible plants.   The preservation was also helped by the fact that the floor of the cave was covered by a thick layer of sheep dung which acted as a solid seal over the objects, preserving them beautifully over the millennia!  

 “We thought initially that the shoe and other objects were about 600-700 years old because they were in such good condition,” said Dr Pinhasi.  “It was only when the material was dated by the two radiocarbon laboratories in Oxford, UK, and in California, US that we realised that the shoe was older by a few hundred years than the shoes worn by Ötzi, the Iceman.”  

Three samples were taken in order to determine the absolute age of the shoe and all three tests produced the same results.  The archaeologists cut two small strips of leather off the shoe and sent one strip to the Oxford Radiocarbon Accelerator Unit at the University of Oxford and another to the University of California –Irvine Accelerator Mass Spectrometry Facility. A piece of grass from the shoe was also sent to Oxford to be dated and both shoe and grass were shown to be the same age.

The shoe was discovered by Armenian PhD student, Ms Diana Zardaryan, of the Institute of Archaeology, Armenia, in a pit that also included a broken pot and  wild goat horns.  “I was amazed to find that even the shoe-laces were preserved,” she recalled.  “We couldn’t believe the discovery,” said Dr Gregory Areshian, Cotsen Institute of Archaeology  at UCLA, US, co-director who was at the site with Mr Boris Gasparyan, co-director, Institute of Archaeology, Armenia  when the shoe was found.  “The crusts had sealed the artefacts and archaeological deposits and artefacts remained fresh dried, just like they were put in a can,” he said.

The oldest known footwear in the world, to the present time, are sandals made of plant material, that were found in a cave in the Arnold Research Cave in Missouri in the US.  Other contemporaneous sandals were found in the Cave of the Warrior, Judean Desert, Israel, but these were not directly dated, so that their age is based on various other associated artefacts found in the cave. 

Interestingly, the shoe is very similar to the ‘pampooties’ worn on the Aran Islands (in the West of Ireland) up to the 1950s.  “In fact, enormous similarities exist between the manufacturing technique and style of this shoe and those found across Europe at later periods, suggesting that this type of shoe was worn for thousands of years across a large and environmentally diverse region,” said Dr Pinhasi.

“We do not know yet what the shoe or other objects were doing in the cave or what the purpose of the cave was,” said Dr Pinhasi.  “We know that there are children’s graves at the back of the cave but so little is known about this period that we cannot say with any certainty why all these different objects were found together.”  The team will continue to excavate the many chambers of the cave.

The team involved in the dig included;  lead author and co-director, Dr Ron Pinhasi, Archaeology Department,  University College Cork, Cork, Ireland;  Mr Boris Gasparian, co-director and Ms Diana Zardaryan  of  the Institute of Archaeology and Enthography, National Academy of Sciences, Republic of Armenia;  Dr Gregory Areshian, co-director,  Research Associate at the Cotsen Institute of Archaeology, University of California, US;  Professor Alexia Smith, Department of Anthropology of the University of Connecticut, US,   Dr Guy Bar-Oz , Zinman Institute of Archaeology,  University of Haifa, Israel and Dr Thomas Higham, Oxford Radiocarbon Accelerator Unit,  University of Oxford, UK.

The research received funding from the National Geographic Society, the Chitjian Foundation (Los Angeles), US, Mr Joe Gfoeller of the Gfoeller Foundation of US, the Steinmetz Family Foundation,US, the Boochever Foundation, US, and the Cotsen Institute of Archaeology, UCLA, US.

Source:Galileo 9/6/10

Barefoot Running - avoids heel strike.

  "All you need to run is a pair of shoes."

Not so!

Scientists have found that those who run barefoot, or in minimal footwear, tend to avoid "heel-striking," and instead land on the ball of the foot or the middle of the foot. In so doing, these runners use the architecture of the foot and leg and some clever Newtonian physics to avoid hurtful and potentially damaging impacts, equivalent to two to three times body weight, that shod heel-strikers repeatedly experience.
"People who don't wear shoes when they run have an astonishingly different strike," says Daniel E. Lieberman, professor of human evolutionary biology at Harvard University and co-author of a paper appearing this week in the journal Nature.

"By landing on the middle or front of the foot, barefoot runners have almost no impact collision, much less than most shod runners generate when they heel-strike. Most people today think barefoot running is dangerous and hurts, but actually you can run barefoot on the world's hardest surfaces without the slightest discomfort and pain. All you need is a few calluses to avoid roughing up the skin of the foot. Further, it might be less injurious than the way some people run in shoes."

Working with populations of runners in the United States and Kenya, Lieberman and his colleagues at Harvard, the University of Glasgow, and Moi University looked at the running gaits of three groups: those who had always run barefoot, those who had always worn shoes, and those who had converted to barefoot running from shod running. The researchers found a striking pattern.

Most shod runners -- more than 75 percent of Americans -- heel-strike, experiencing a very large and sudden collision force about 1,000 times per mile run. People who run barefoot, however, tend to land with a springy step towards the middle or front of the foot.
"Heel-striking is painful when barefoot or in minimal shoes because it causes a large collisional force each time a foot lands on the ground," says co-author Madhusudhan Venkadesan, a postdoctoral researcher in applied mathematics and human evolutionary biology at Harvard. "Barefoot runners point their toes more at landing, avoiding this collision by decreasing the effective mass of the foot that comes to a sudden stop when you land, and by having a more compliant, or springy, leg."

The differences between shod and unshod running have evolutionary underpinnings. For example, says Lieberman, our early Australopith ancestors had less developed arches in their feet. Homo sapiens, by contrast, has evolved a strong, large arch that we use as a spring when running.

"Our feet were made in part for running," Lieberman says. But as he and his co-authors write in Nature: "Humans have engaged in endurance running for millions of years, but the modern running shoe was not invented until the 1970s. For most of human evolutionary history, runners were either barefoot or wore minimal footwear such as sandals or moccasins with smaller heels and little cushioning."

For modern humans who have grown up wearing shoes, barefoot or minimal shoe running is something to be eased into, warns Lieberman. Modern running shoes are designed to make heel-striking easy and comfortable. The padded heel cushions the force of the impact, making heel-striking less punishing.

"Running barefoot or in minimal shoes is fun but uses different muscles," says Lieberman. "If you've been a heel-striker all your life you have to transition slowly to build strength in your calf and foot muscles."
In the future, he hopes, the kind of work done in this paper can not only investigate barefoot running, but can provide insight into how to better prevent the repetitive stress injuries that afflict a high percentage of runners today.

"Our hope is that an evolutionary medicine approach to running and sports injury can help people run better for longer and feel better while they do it," says Lieberman, who has created a web site, www.barefootrunning.fas.harvard.edu, to educate runners about the respective merits of shod and barefoot running.

Source:Science Daily 2010

Human Gait Adapted for Efficient Walking at the Cost of Efficient Running

Humans, other great apes and bears are among the few animals that step first on the heel when walking, and then roll onto the ball of the foot and toes. Now, a University of Utah study shows the advantage: Compared with heel-first walking, it takes 53 percent more energy to walk on the balls of your feet, and 83 percent more energy to walk on your toes."Our heel touches the ground at the start of each step. In most mammals, the heel remains elevated during walking and running," says biology Professor David Carrier.

"Most mammals -- dogs, cats, raccoons -- walk and run around on the balls of their feet. Ungulates like horses and deer run and walk on their tiptoes," he adds. "Few species land on their heel: bears and humans and other great apes -- chimps, gorillas, orangutans."

"Our study shows that the heel-down posture increases the economy of walking but not the economy of running," says Carrier. "You consume more energy when you walk on the balls of your feet or your toes than when you walk heels first."
Economical walking would have helped early human hunter-gatherers find food, he says. Yet, because other great apes also are heel-first walkers, it means the trait evolved before our common ancestors descended from the trees, he adds.
"We [human ancestors] had this foot posture when we were up in the trees," Carrier says. "Heel-first walking was there in the great apes, but great apes don't walk long distances. So economy of walking probably doesn't explain this foot posture [and why it evolved], even though it helps us to walk economically."
Carrier speculates that a heel-first foot posture "may be advantageous during fighting by increasing stability and applying more torque to the ground to twist, push and shove. And it increases agility in rapid turning maneuvers during aggressive encounters."
The study concludes: "Relative to other mammals, humans are economical walkers but not economical runners. Given the great distances hunter-gatherers travel, it is not surprising that humans retained a foot posture, inherited from our more arboreal [tree-dwelling] great ape ancestors, that facilitates economical walking."

Measuring the Costs of Different Modes of Walking and Running

Carrier conducted the study with Christopher Cunningham, a doctoral student in biology at the University of Utah; Nadja Schilling, a zoologist at Friedrich Schiller University of Jena, Germany; and Christoph Anders, a physician at University Hospital Jena. The study was funded by the National Science Foundation, Friedrich Schiller University of Jena and a German food industry insurance group interested in back pain.
The study involved 27 volunteers, mostly athletes in their 20s, 30s and 40s. Each subject walked or ran three different ways, with each step either heel-first, ball-of-foot first with the heel a bit elevated or toes first with the heel even more elevated.
In his lab, Carrier and colleagues measured oxygen consumption -- and thus energy use -- as 11 volunteers wore face masks while walking or running on a treadmill. They also walked on a "force plate" to measure forces exerted on the ground.
Part of the study was conducted at Anders' lab in Germany, where 16 people walked or ran on a treadmill as scientists monitored activity of muscles that help the ankles, knees, hips and back do work during walking and running.
Findings of the experiments included:

• "You consume more energy when you walk on the balls of your feet or your toes than when you walk heels-first," Carrier says. Compared with heels-first walkers, those stepping first on the balls of their feet used 53 percent more energy, and those stepping toes-first expended 83 percent more energy.

• "The activity of the major muscles of the ankle, knee, hip and back all increase if you walk on the balls of your feet or your toes as opposed to landing on your heels," says Carrier. "That tells us the muscles increase the amount of work they are producing if you walk on the balls of your feet."

• "When we walk on the balls of our feet, we take shorter, more frequent strides," Carrier says. "But this did not make walking less economical." Putting the heel down first and pivoting onto the ball of the foot makes the stride longer because the full length of the foot is added to the length of the step. But that has no effect on energy use.

• The researchers wondered if stepping first on the balls of the feet took more energy than walking heel-first because people are less stable on their toes or balls of the feet. But increased stability did not explain why heel-first walking uses less energy.

• Stepping heel-first reduced the up-and-down motion of the body's center of mass during walking and required less work by the hips, knees and ankles. Stepping first onto the balls of the feet slows the body more and requires more re-acceleration.

• Heels-first steps also made walking more economical by increasing the transfer of movement or "kinetic" energy to stored or "potential" energy and back again. As a person starts to step forward and downward, stored energy is changed to motion or kinetic energy. Then, as weight shifts onto the foot and the person moved forward and upward, their speed slows down, so the kinetic energy of motion is converted back into stored or potential energy. The study found that stepping first onto the balls of the feet made this energy exchange less efficient that walking heels-first.

• Heel-first walking also reduced the "ground reaction force moment" at the ankle. That means stepping first onto the ball of the foot "decreases the leverage, decreases the mechanical advantage" compared with walking heel-first, Carrier says.

In sum, walking heel-first is not more economical because it is more stable or involves fewer, longer strides, but because when we land on our heels, less energy is lost to the ground, we have more leverage, and kinetic and potential energy are converted more efficiently.

Form and Function of the Foot

If heel-first walking is so economical, why do so many animals walk other ways?
"They are adapted for running," Carrier says. "They've compromised their economy of walking for the economy of running."
"Humans are very good at running long distances. We are physiologically and anatomically specialized for running long distances. But the anatomy of our feet is not consistent with economical running. Think of all the animals that are the best runners -- gazelles, deer, horses, dogs -- they all run on the ball of their feet or the tips of their toes."
When people run, why is there no difference in the amount of energy they expend when stepping first onto their heels versus the balls of their feet or toes?
The answer is unknown, but "if you land on your heel when you run, the force underneath the foot shoots very quickly to the ball of your foot," Carrier says. "Even when we run with a heel plant, most of the step our weight is supported by the ball of our foot. Lots of elite athletes, whether sprinters or distance runners, don't land on their heel. Many of them run on the balls of their feet," as do people who run barefoot. That appears to be the natural ancestral condition for early human runners, he adds.
"The important thing is we are remarkable economical walkers," Carrier says. "We are not efficient runners. In fact, we consume more energy to run than the typical mammal our size. But we are exceptionally economical walkers."
"This study suggests that one of the things that may explain such economy is the unusual structure of our foot," he adds. "The whole foot contacts the ground when we walk. We have a big heel. Our big toe is as long as our other toes and is much more robust. Our big toe also is parallel to and right next to the second toe."
"These features are distinct among apes, and provide the mechanical basis for economical walking. No other primate or mammal could fit into human shoes."

---

Reference:

1. Cunningham, C. B., Schilling, N., Anders, C. and Carrier, D. R. The influence of foot posture on the cost of transport in humans. J. Exp. Biol., 213, 790-797

ScienceDaily (Feb. 12, 2010) 

Neolithic Amputation...anaesthetic and aseptic.

Scientists unearthed evidence of surgery carried out in ancient times during work on an Early Neolithic tomb discovered at Buthiers-Boulancourt, about 65km south of Paris. They found that a remarkable degree of medical knowledge had been used to remove the left forearm of an elderly man about 6,900 years ago. The patient seems to have been anaesthetised, the conditions were aseptic, the cut was clean and the wound was treated, according to the French National Institute for Preventive Archaeological Research .

The revelation could force a reassessment of the history of surgery, especially because researchers have recently reported signs of two other Neolithic amputations in Germany and the Czech Republic. It was known that Stone Age doctors performed trephinations, cutting through the skull, but not amputations. "The first European farmers were therefore capable of quite sophisticated surgical acts."

The discovery was made by Cécile Buquet-Marcon and Anaick Samzun, both archaeologists, and Philippe Charlier, a forensic scientist. It followed research on the tomb of an elderly man who lived in the Linearbandkeramik period, when European hunter-gatherers settled down to agriculture, stock-breeding and pottery. The patient was important: his grave was 2m long - bigger than most - and contained a schist axe, a flint pick and the remains of a young animal, which are evidence of high status. The most intriguing aspect, however, was the absence of forearm and hand bones. A battery of biological, radiological and other tests showed that the humerus bone had been cut above the trochlea indent at the end 'in an intentional and successful amputation'.

Mrs Buquet-Marcon said that the patient, who is likely to have been a warrior, might have damaged his arm in a fall, animal attack or battle, she said "I don't think you could say that those who carried out the operation were doctors in the modern sense that they did only that, but they obviously had medical knowledge," 

A flintstone almost certainly served as a scalpel. Mrs Buquet-Marcon said that pain-killing plants were likely to have been used, perhaps the hallucinogenic Datura. "We don't know for sure, but they would have had to find some way of keeping him still during the operation," she said. Other plants, possibly sage, were probably used to clean the wound. "The macroscopic examination has not revealed any infection in contact with this amputation, suggesting that it was conducted in relatively aseptic conditions," said the scientists in an article for the journal Antiquity.

The patient survived the operation and, although he suffered from osteoarthritis, he certainly lived for months, perhaps years, afterwards. Despite the loss of his forearm, the contents of his grave showed that he remained part of the community. "His disability did not exclude him from the group," the researchers said. The discovery demonstrates that advanced medical knowledge and complex social rules were present in Europe in about 4900 BCE, and that major surgery was likely to have been more common than we realised, stated Mrs Buquet-Marcon.

Image credit: Hulton

Return to the Hobbit ...brain/body mass differ in selection process

Homo floresiensis, a pygmy-sized small-brained hominin popularly known as ‘the Hobbit’ was discovered five years ago, but controversy continues over whether the small brain is actually due to a pathological condition. How can its tiny brain size be explained? Researchers have tackled this question in the context of a comprehensive assessment of the evolution of brain and body size throughout the larger primate family.

Nick Mundy and Stephen Montgomery, from the Department of Zoology at Cambridge University, UK, and colleagues from Durham University used previously published data from living and extinct species to reconstruct the pattern of brain and body mass evolution in primates. According to Nick Mundy, “Our results provide robust confirmation for the suggestion that strong evolutionary trends have governed the expansion of the primate brain. In contrast, body size evolution has not tended to increase in primates, implying brain and body mass have been subject to separate selection pressures and supporting the findings of previous studies in other taxonomic groups that these two highly correlated traits can show differences in their patterns of evolution”.

Brain expansion began early in primate evolution and has occurred in all major groups, suggesting a strong selective advantage to increased brainpower in most primate lineages. Despite this overall trend, however, Mundy and his colleagues have identified several branches/lineages within each major group that have shown decreasing brain and body mass as they evolve, for example in marmosets and mouse lemurs. According to Mundy, “We find that, under reasonable assumptions, the reduction in brain size during the evolution of Homo floresiensis is not unusual in comparison to these other primates. Along with other recent studies on the effects of ‘island dwarfism’ in other mammals, these results support the hypothesis that the small brain of Homo floresiensis was adapted to local ecological conditions on Flores."

http://www.biomedcentral.com/bmcbiol/

Source: Alphagalileo 27/01/10

Evolution of the Human Gait

Professor Matthew Bennett has been awarded a Standard Natural Environment Research Council (NERC) grant worth £880,000, in collaboration with Professor Robin Compton of Liverpool University, to continue research into the evolution of the human gait in our ancestors.
In 2009, Professor Bennett was the lead author of a landmark paper published in the acclaimed journal Science which revealed new evidence of early human development. The study, which featured on the front cover of Science, concluded that footprints discovered near Ileret in Northern Kenya were left by one of our evolutionary ancestors, Homo erectus.
Professor Bennett and an international team of colleagues believe that the prints, made between 1.51 and 1.53 million years ago, show clear evidence that Homo erectus had a modern foot anatomy and function, and walked much like we do today. This important feature is viewed as vital to the shift in cultural and biological adaptations of Homo erectus, believed to be the first species to migrate from Africa.
The footprints are preserved in fine-grained mud on two distinct sedimentary layers in a single outcrop at Ileret. These surfaces have been dated precisely via volcanic ash layers and digitally scanned by Professor Bennett to create three-dimensional digital elevation models accurate to a fraction of a millimeter. Laser scanning not only provides a unique method of analysis, but also allows for the footprints to be preserved where they are and shared digitally around the world.
“I’m delighted that Professor Compton and I have been successful in obtaining this funding which will mean that our work on these ancient footprints can continue,” said Professor Bennett. “The award will help to fund vital resources in the lab and in the field and should lead us to uncovering further evidence of early man’s development.”

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. 

'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.

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

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:
http://www.benhallphotography.com/
Read about Charles Darwin's time in South America here:
http://darwin-online.org.uk/
Read Charles Darwin's letters here:
http://www.darwinproject.ac.uk/
Dinosaur evolution
http://www.seaes.manchester.ac.uk/research/groups/palaeo/themes/gaitmodelling/
Evolution of birds
http://www.seaes.manchester.ac.uk/research/groups/palaeo/themes/gaitmodelling/
Evolution of microbes
http://www.ls.manchester.ac.uk/research/themes/evolution/researchtopics/microbialevolution/
Molecular evolution
http://www.ls.manchester.ac.uk/research/themes/bioinformatics/researchtopics/molecularevolution/

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.

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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

"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.”

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

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

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

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.