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Reconstructing the Diet of African Hominid Australopithecus Anamensis
The work, published in the Journal of Anthropological Sciences, is directed by lecturer Alejandro Pérez Pérez, from the Anthropology Unit of the Department of Animal Biology at the UB, and its co-authors are professor Daniel Turbón and experts Jordi Galbany and Laura M. Martínez.
Australipithecus anamensis is a fossil hominid species described in 1995 by a team led by the researcher Meave Leakey and it is considered to be the direct ancestor of Australopithecus afarensis, known as Lucy, which lived in the same region half a million years later. The paleoecological reconstructions of the sites with Australipithecus anamensis fossil remains are quite similar to those of Australipithecus afarensis, and suggest a scene with different habitats, from open forests to thick plant formations, with herbaceous strata and gallery forests.
Traditionally, the reconstruction of the diet of Australipithecus anamensis was carried out by means of indirect evidence (specifically, studies of microstructure and enamel thickness, and the dental size and morphology). In this new study, the team of the UB analyzes the pattern of microstriation of the post-canine dentition, from microscopic traces that some structural components of plants (phytoliths) and other external elements (sand, dust, etc.) leave in the dental enamel during the chewing of food. It is, therefore, a direct analysis of the result of the interaction of the diet with the teeth.
A cercopithecoid model for the study of the diet
The work published in the Journal of Anthropological Sciences studies the microstriation pattern of all the specimens of Australipithecus anamensis recovered up to the year 2003, of which only five are in a good state of preservation. According to the study of the microstriation pattern, the diet of Anthropological anamensis was similar to other present day species of cercopithecoid primates, such as Papio genus(baboons) and Chlorocebus (green monkey), which live in shrubby savannah areas with a marked seasonal influence. The work arrived at the conclusion that the diet of Australipithecus anamensis was quite abrasive and rich in seeds, leaves and corms, as it is with the baboons of today. This fossil hominid must also have fed on fruit, but in smaller proportions than Australipithecus afarensis.
What did Australopithecus afarensis eat?
The results of the study on the palaeodiet of Australipithecus anamensis match the characteristics of dental morphology and increased robustness of the dentition and the masticatory apparatus compared with its ancestor, Ardipithecus ramidus. The new questions now focus on the diet of Australipithecus afarensis, direct descendent of Australipithecus anamensis, which has a frugivorous and much softer diet, like present day chimpanzees and gorillas in Cameroon.
As explained by the researcher Ferran Estebaranz,"the microstriation pattern of Australipithecus anamensis and Australipithecus afarensis is clearly different. This could indicate that the former consumed much harder foodstuffs, whereas the latter had a basically frugivorous diet, of a seasonal character, more similar to the direct ancestor of the two species, Ardipithecus ramidus."
Ancient Human Ancestors Had Unique Diet
The study indicated that Australopithecus sediba -- a short, gangly hominid that lived in South Africa -- ate harder foods than other early hominids, targeting trees, bushes and fruits. In contrast, virtually all other ancient human ancestors tested from Africa -- including Paranthropus boisei, dubbed "Nutcracker Man" because of its massive jaws and teeth -- focused more on grasses and sedges, said CU-Boulder doctoral student Paul Sandberg, a co-author on the new study.
The A. sediba diet was analyzed using a technique that involved zapping fossilized teeth with a laser, said Sandberg. The laser frees telltale carbon from the enamel of teeth, allowing scientists to pinpoint the types of plants that were consumed and the environments in which the hominids lived. The carbon signals from the teeth are split into two groups: C3 plants like trees, shrubs and bushes preferred by A. sediba, and C4 plants like grasses and sedges consumed by many other early hominids.
The teeth from the two A. sediba individuals analyzed in the study had carbon isotope values outside the range of all 81 previously tested hominids. "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," said Sandberg.
"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," said Sandberg of CU-Boulder's anthropology department.
The researchers concluded from their scientific tests that bark and other fracture-resistant foods were at least a seasonal part of the A. sediba diet. While bark and woody tissues had not been previously documented as a dietary component of any other ancient African hominids, such foods are consumed by many contemporary primates and contain both protein and soluble sugars. The diet of A. sediba may have been similar to that of today's African savanna chimpanzees, Sandberg said.
One unique aspect of the project was the analysis of microscopic, fossilized particles of plant tissue known as phytoliths trapped in ancient tooth tarter, a hardened form of dental plaque, said corresponding study author Amanda Henry of the Max Planck Institute for Evolutionary Anthropology.
"The fact that these phytoliths are preserved in the teeth of 2 million-year-old hominids is remarkable and speaks to the amazing preservation at the site," said Sandberg. "The phytolith data suggest the A. sediba individuals were avoiding the grasses growing in open grasslands that were abundant in the region at the time."
A third, independent line of study -- analyzing microscopic pits and scratches on A. sediba teeth, which reveal what they were eating at the time just prior to death -- also confirmed that at least one of the hominids was eating harder foods, said Sandberg.
A paper on the subject was published online by Nature on June 27. Other paper authors included Professor Matt Sponheimer of CU-Boulder, Peter Ungar of the University of Arkansas, Benjamin Passey of Johns Hopkins University, Lloyd Rossouw of the Bloemfontein National Museum in Bloemfontein, South Africa, Lee Berger and Marion Bamford of the University of Witwatersrand in Johannesburg, South Africa and Darryl de Ruiter of Texas A&M University.
A. sediba is particularly intriguing to anthropologists. The first two individuals discovered -- a juvenile male and an adult female from the Malapa Cave site roughly 30 miles north of Johannesburg in 2008 --apparently had fallen into a hidden pit in the cave and died. With an upright posture and long arms, the curious creature appears to have characteristics of both primitive and modern hominids, including a human-like ankle, short fingers and a long thumb for possible precision gripping and a relatively complex brain compared to earlier hominids, according to researchers.
The jury is still out on exactly where these hominids land on the family tree. A. sediba may have been a descendant of A. africanus, which was spawned by A. afarensis, a hominid represented by "Lucy" who lived about three million years ago and is considered by many to be the matriarch of the human family.
The A. sediba remains at Malapa were dated to 2 million years by scientists, a precise number obtained by measuring the decay of isotopes of uranium into lead that occurred in a type of mineral deposit known as flowstone that capped the fossil-bearing layer.
Paleontological evidence, including pollen and phytoliths, shows that the region around Malapa likely was a mix of abundant grassland and woody vegetation about 2 million years ago, said Sandberg. The team's carbon isotope research on the ancient teeth of rodents and hooved mammals that inhabited the region at the time indicated they had a strong affinity for C4 grasses and sedges.
"What fascinates me is that these individuals are oddballs," said CU-Boulder's Sponheimer. "I had pretty much convinced myself that after four million years ago most of our hominid kin had diets that were different from living apes, but now I am not so sure. And while our sample is too small to be conclusive, the rate at which Malapa is spewing hominid fossils makes me reasonably certain we won't have to wait another two million years to augment our data set. "
The study was funded in part by the National Science Foundation, the Smithsonian Institution, the Malapa Project at the Institute for Human Evolution at the University of Witwatersrand and the Max Planck Society.
Quick News: Primitive humans turned dinosaur fossils into weapons
A group of researchers on Sunday claimed that it had found evidence that the primitive humans living in the Narmada valley thousands of years ago used the fossils of dinosaurs to make weapons.
Vishal Verma of Mangal Panchayat Parishad,
a group which undertakes archaeological excavations in the area, said
that eight weapons of this kind were found in the neighbouring Dhar district during a recent expedition.
They included an axe, and something resembling a blade.
He
said presumably the primitive humans were not aware that "stones" out
of which they were fashioning weapons were actually fossils.
Handsome By Chance: Why Humans Look Different From Neanderthals
Chance, not natural selection, best explains why the modern human skull looks so different from that of its Neanderthal relative, according to a new study led by Tim Weaver, assistant professor of anthropology at UC Davis.
"For 150 years, scientists have tried to decipher why Neanderthal skulls are different from those of modern humans," Weaver said. "Most accounts have emphasized natural selection and the possible adaptive value of either Neanderthal or modern human traits. We show that instead, random changes over the past 500,000 years or so – since Neanderthals and modern humans became isolated from each other – are the best explanation for these differences."
Weaver and his colleagues compared cranial measurements of 2,524 modern human skulls and 20 Neanderthal specimens, then contrasted those results with genetic information from a separate sample of 1,056 modern humans.
The scientists concluded that Neanderthals did not develop their protruding mid-faces as an adaptation to icy Pleistocene weather or the demands of using teeth as tools, and the retracted faces of modern humans are not an adaptation for language, as some anthropologists have proposed.
Instead, random "genetic drift" is the likeliest reason for these skull differences.
Weaver conducted the research with Charles Roseman, an anthropologist at the University of Illinois at Urbana-Champaign, and Chris Stringer, a paleoanthropologist at the Natural History Museum in London.
