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

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

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

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."

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. 8/1/09

Life on Earth got bigger in 2-million-fold leaps, our feet had to start somewhere!

Extremes are exciting. Does anyone really think dinosaurs would capture our imagination the way they do if they hadn't been so huge? You don't see natural history museums vying for fossil skeletons of prehistoric rodents. It's the Tyrannosaurus rex fossils they salivate and squabble over. And would the Hollywood glitterati cart around those little teacup pups if they weren't so dang tiny and cute? Not likely.
Earth's creatures come in all sizes, yet they (and we) all sprang from the same single-celled organisms that first populated the planet. So how on Earth did life go from bacteria to the blue whale?
"It happened primarily in two great leaps, and each time, the maximum size of life jumped up by a factor of about a million," said Jonathan Payne, assistant professor of geological and environmental science at Stanford.
Payne, along with a dozen other paleontologists and ecologists at 10 different research institutions, pooled their existing databases, combed the scientific literature and consulted with taxonomic experts in a quest to determine the maximum size of life over all of geological time.
That might sound like a rather large undertaking, but, fortunately, the quest was made easier because even the professionals have a fascination with the size of the fossilized.
"The nice thing about maximum size is that people tend to remark on very large fossils, so they are much easier to track down in the geologic literature than anything else," Payne said.
In addition to quantifying the enormity of the two leaps in maximum size, the researchers also pinned down when those leaps took place. Both leaps coincided with periods when there was a major increase in the amount of oxygen in the atmosphere.
Payne said that many researchers already recognized, in a qualitative way, that the change in maximum size had occurred this way. "But our study really reflects the first time that anybody has tried to quantify exactly how stepwise it was and how big those size jumps were," he said.
A paper detailing the research by Payne and his colleagues is scheduled to be published in the Dec. 22, 2008, online early edition of the Proceedings of the National Academy of Sciences and is available online through EurekAlert.
The two other principal investigators of the research group, funded through the National Evolutionary Synthesis Center, are Michal Kowalewski of Virginia Tech and Jennifer Stempien of the University of Colorado-Boulder.
So how did it all happen? The first fossilized bacterial cells date to approximately 3.4 billion years ago, although life likely originated several hundred million years before. Between 2.7 and 2.4 billion years ago, cyanobacteria, formerly known as blue-green algae, originated and were of particular evolutionary and geological importance because they excrete oxygen as a waste product during photosynthesis. So far as science can tell, they were the first and only organisms to evolve oxygen-producing photosynthesis.
"All of the oxygen in the atmosphere ultimately exists because of the evolution of cyanobacteria," Payne said. "Plants that produce oxygen today during photosynthesis, their ability to do that is ultimately derived from cyanobacteria."
Single-celled bacteria remained the largest life form on Earth, cranking out the oxygen, until about 1.6 billion years ago. At that point, a new life form shows up in the fossil record.
"The first jump in maximum size happens when the first eukaryotic organisms show up as fossils," Payne said. "And those fossils are approximately a million times bigger than anything that had come before on Earth."
Although the first fossil eukaryotes were likely also single-celled organisms, the eukaryotes distinguish themselves by means of their internal structure and functioning. Instead of having the cellular processes of life take place by means of diffusion in the cell, eukaryotes have organized innards, with a nucleus and other cellular structures that are dedicated to specific functions in the respiratory process.
"The fossil record indicates pretty clearly that you need a eukaryotic cell to make that first size jump," Payne said. "It isn't just that the bacteria don't get there as fast, it is that bacteria still haven't gotten there 1.6 billion years later.
"Clearly, organismal organization matters," Payne said. "Not just at the time the size increase happens, but it continues to be a limitation on size.
For approximately the next billion years, life on Earth stayed about the same size, with only modest increases. Then about 600 million years ago, at the same time as another major boost in the amount of oxygen in the atmosphere, life leaped in size again.
This time, it was a million-fold size leap of multi-cellularity. Payne said there are clearly multi-cellular eukaryotes in the fossil record for several million years before this size leap, but the real explosion of size increase didn't happen until the oxygen level bumped up.
So why do the size leaps seem to hinge on the amount of oxygen in the air?
"There are a few things that could be going on," Payne said. "The first thing is that eukaryotic cells require oxygen for metabolism. So if they want to take organic matter and burn it up to have energy in their cell, they need oxygen. That sets the first and probably most important limitation."
Payne said this limitation also applies to multi-cellular eukaryotes, which likewise depend on extracting oxygen from the surrounding environment and using that in their cells to obtain energy. "There is also evidence that oxygen may mediate some other biochemical processes," he said.
As for just what triggered both the boosts in atmospheric oxygen, Payne said that isn't quite as clear. It may be that the first jump in oxygen came because cyanobacteria simply proliferated to the point that they were cranking out more oxygen than could be consumed through chemical reactions with material at Earth's surface, the only way that oxygen wouldn't have been released back into the atmosphere in the era before oxygen breathing creatures existed.
The possible causes of the second jump in oxygen are less clear, Payne said, but regardless of the puzzles that remain to be sorted out, the timing and magnitude of the jumps up in maximum size are clear. And Payne said the size jumps applied to a vast number of species.
"Whatever is controlling this second size increase appears to operate across many different groups. It is not something limiting one group alone," he said. "There also appears to be an increase even in the maximum size of groups of organisms like multi-cellular algae, so the size increase doesn't appear to be limited just to animals."
One other question remains to be answered: Can we look forward to another great leap in size? Will we see housecats larger than our houses?
"We've speculated on that a little bit, just sort of thinking about what if you went up another step," Payne said.
"The next level of organization, going along this kind of theme, presumably would be something like insect societies, where you have individual multicellular eukaryotes that specialize in terms of what kind of function they carry out in a larger organization of these individuals. Something like an ant colony or a human society would be in some ways the next organizational level.
"But, if you look at human society as an example, we use so much of the gross primary productivity on Earth, it doesn't appear there would be room for a lot of species at that next level of organization and maximum size. At that point you're actually getting towards the physical size limits just imposed by the size of our planet."

Source:Eurekalert 23/12/08.

Gibbon feet provide model for early human walking.

Scientists at the University of Liverpool have found that early humans could have walked successfully on a ‘flexible’ flat foot, similar to modern day gibbons.The arched ‘rigid’ foot of modern humans – thought to have appeared approximately 1.8 million years ago – is best adapted for upright walking, but scientists have found that early humans once had ‘flexible’ feet and could have walked on the ground some years earlier. Scientists originally thought that a flexible foot could have been ‘restrictive’ for humans learning to walk upright as it lacked the necessary power to push off the ground. To understand the mechanisms of the flexible foot, scientists studied the movements of gibbons – small apes living in the rainforest of South East Asia – which walk upright both on the ground and in the trees.Dr Evie Vereecke, from the University’s School of Biomedical Sciences, explains: “Gibbons have a flexible joint mid-way along the foot that supports them in walking and climbing. Human ancestors also had this joint for tree dwelling and ground walking, but modern humans have now lost its flexibility in favour of a ‘rigid’ foot. “To understand how successful or ‘restrictive’ the flexible foot might have been for early humans we set up a high-speed camera at Belgium’s Wild Animal Park to capture the gibbon’s foot movements. We built a computer model to digitise the footage we collected so that we could analyse the mechanisms employed in the foot and compare it to how humans walk today. “We found that gibbons hit the ground with their toes first, similar to the ‘forefoot’ strike of professional sprint runners, which stretches the tendons in the toes. We also found that instead of lifting the foot at the end of a stride, the gibbon raised its heel first, making an upward arch and stretching the tendons in the sole of the foot.“These stretched tendons allow storage of elastic energy and once the toe leaves the ground the tendons in the foot recoil, releasing the stored energy and generating the necessary propulsion to push off the ground and walk upright quite successfully. “The structure of the modern human foot is different to the gibbon, but the energy storage mechanism is similar. The human foot is spanned by an elastic band along its sole which is stretched when we put our weight on it and stores elastic energy ready for release when the foot leaves the ground.”The work - published in the Journal of Experimental Biology - shows that it is possible that human ancestors could have walked successfully with an upright-gait on a ‘flexible’ flat foot and may have similar energy storage mechanisms to modern humans.

Source:The University of Liverpool 17/12/08.