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.”