Diets ancestors of humans and chimpanzees diverged 3 million years ago

Paleontologists compared the proportion of carbon isotopes in the tooth enamel of Australopithecus, and found that the ancestors of humans and chimpanzees have moved to different diets 3 million years ago, 1.5 million years earlier than previously thought, according to a paper published in the journal Proceedings of the National Academy of Sciences.

In the last decade, paleontologists have noted that the fossil teeth of mammals are keeping the traces of their diet. For example, the ratio of carbon isotopes in the teeth of ancient hominids, you can determine whether they ate leaves and fruit of plants from the forest or the African savannah. For example, a high proportion of 'heavy' carbon-13 in the teeth of Paranthropus, who lived in Africa 1.5 million years ago, pointed out that at this time our ancestors lived on the plains and eat the fruit of their flora.

Group of paleontologists led by Julia Lee-Thorp (Julia Lee-Thorp) from Oxford University (UK) studied the remains of Australopithecus (Australopithecus bahrelghazali), who lived in central Africa about 3,5-3 million years ago.

These australopithecines were opened by one of the authors, Michel Brunet (Michel Brunet) of the University of Poitiers (France) in 1993 during excavations in the ancient dried-up channel of the river Bahr el Ghazal, near Lake Chad. According to scientists, three million years ago on the banks of the lake existed as tracts of forests and steppes, which does not allow to classify Australopithecus bahrelghazali to forest or steppe inhabitants.

Lee-Thorp and her colleagues have tried to solve this puzzle by studying the chemical composition of the enamel Australopithecus bahrelghazali and defining the type of diet. To do this, scientists have separated a few pieces of the enamel of fossil teeth of Australopithecus with a laser, crush them, and calculated the proportion of the atoms of the "heavy" carbon-13 in them. They then compared this figure with a similar proportion to the teeth of herbivorous animals — antelope and giraffe, whose remains lie in the same layer on the shores of Lake Chad.

Herbaceous plants use more efficient mechanism of photosynthesis (C4), which among other things allows them to capture and process the "heavy" carbon dioxide. This mechanism is not effective if the plant is getting enough light, whereby forest plants use less efficient "tree" method of photosynthesis (C3). Therefore, the relative abundance of carbon-13 in tooth enamel can tell scientists what type of food fed ancient protolyudi.

It turned out that the teeth Australopithecus bahrelghazali contain a relatively high proportion of carbon-13, comparable with those of the typical inhabitants of the savannahs. Scientists have calculated that about 55-80% of their diet, fruits and leaves of herbaceous plants. Lee-Thorp and her colleagues believe that the basis of the diet of Australopithecus were fruits and roots, as the leaves and stems of steppe flora contain too many "non-food" particulate silicon and hard fibers.

Such a diet is very different from the direct ancestors of the chimpanzee diet, eating fruit and tree leaves. Scientists believe the difference in food preferences protolyudey and ancient primates suggests that the ancestors of the people have moved to the "steppe" diet is not 1.5 million years ago, as previously thought, and 3 million years ago.

This assumption will stand the test of criticism. For example, it is not clear whether a similar diet typical for neighbors Australopithecus bahrelghazali — Southern Australopithecus Australopithecus africanus, as well as other ancient hominids.

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