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Ancient Human Predecessors Were Tree-Climbing Bark Eaters

June 28, 2012
Image Caption: Upper jaw of the hominin Malapa: close-up of plaque on the front premolar. Credit: © Amanda Henry

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redOrbit Staff & Wire Reports – Your Universe Online

An international team of scientists has revealed that the ancestors of modern humans had an unusual diet — one which may have contributed to their ultimate downfall, according to various reports published Wednesday.

According to Thomas H. Maugh II of the Los Angeles Times, researchers led by the Max Planck Institute of Evolutionary Anthropology in Leipzig, Germany have discovered that Australopithecus sediba, a two-million year old hominid from South Africa, did not consume grasses and wild animals like other pre-humans that have been studied. Rather, they lived on bark, woody tissues, fruits, and other forest plants.

Furthermore, New York Times writer John Noble Wilford said that the scientists found that the A. sediba diet was apparently not forced upon them out of necessity. Rather, Wilford said, animal fossils and sediments found in the vicinity showed that there was plenty of savannah terrain near where they lived, suggesting that it was their decision to eat the things that they did.

Paul Sandberg, a co-author of the study and a doctoral student at the University of Colorado at Boulder (CU-Boulder) anthropology department, said in June 27 statement that the researchers made their discovery by analyzing fossilized A. sediba teeth with a laser that freed carbon from the enamel.

This technique allowed scientists to determine what types of plants the subject had eaten and what type of environment they had been living in. Those carbon signals are split into two categories — C3 plants (trees, shrubs, and bushes) and C4 plants (grasses, sedges, etc.)

“The lack of any C4 evidence, and the evidence for the consumption of hard objects, are what make the inferred diet of these individuals compelling,” Sandberg said. “It is an important finding because diet is one of the fundamental aspects of an animal, one that drives its behavior and ecological niche. As environments change over time because of shifting climates, animals are generally forced to either move or to adapt to their new surroundings.”

“By examining material recovered from their teeth using diverse tools ranging from dental picks and laser ablation devices, we were able to determine precisely what they were eating,” Darryl de Ruiter, an associate professor in the Texas A&M Department of Anthropology and another member of the research team, added in a separate statement. “This gives us a very clear picture of their diet, and it was surprising. It shows that they ate more fruits and leaves than any other hominin fossil ever examined, more like what a chimp might eat.”

De Reuiter added that they found no evidence of A. sediba eating native grasses found in the area at that time, even though that is what previous research has shown that other australopiths living in the same region had consumed. He said that their diet consisted largely of fruit, tree bark, nuts, leaves, and plants like cypress of papyrus. They may have also obtained some animal protein through meat or insects, but additional research is required to prove or disprove that theory, de Reuiter added.

The researchers, who were led by Max Planck Institute anthropologist Amanda Henry, studied fossilized plaque (also known as calculus) on A. sediba remains, using a dental pick to remove the calculus and then using a microscope to look for tiny silica remains of plants known as phytoliths, reported Mariette Le Roux of AFP. Henry said that this was the first time that experts had sought out phytoliths in fossilized plaque to determine a hominin species’ diet.

Their findings will be published by the journal Nature.

Another member of the research team, Johns Hopkins University geochemist Benjamin Passey said that he and his colleagues were “astonished” by their discovery, adding in a press release, “Most hominin species appear to have been pretty good at eating what was around them and available, but sediba seems to have been unusual in that, like present-day chimpanzees, it ignored available savanna foods.”

“We know that if you are a hominin, in order to get to the rest of the world, at some point you must leave the forests, and our ancestors apparently did so,” Passey added. “The fates of those that did not leave are well-known: They are extinct or, like the chimpanzee and gorilla today, are in enormous peril. So the closing chapter in the story of hominin evolution is the story of these ‘dids’ and ‘did nots.’”

Henry also told Le Roux that A. sediba walked upright on two legs, but had a unique foot structure which suggests that it might have spent much of its time climbing trees. Likewise, she told BBC News reporter Helen Briggs that the species was short and primitive, had a small brain and long arms, but was nonetheless somehow related to modern man.


Source: redOrbit Staff & Wire Reports - Your Universe Online



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