For the human ancestor Australopithecus, meat was not on the menu

By Will Dunham

(Reuters) – The introduction of meat into the diet was a milestone in the human evolutionary line and a potential catalyst for advances such as brain enlargement. However, scientists are having difficulty figuring out when and who started eating meat.

New research provides the first direct evidence that Australopithecus, an important early human ancestor that exhibited a mix of ape- and human-like features, consumed very little or no meat and relied on a plant-based diet. The study determined the diet of seven Australopithecus individuals from South Africa 3.7 to 3.3 million years ago based on the chemistry of their tooth enamel.

“Meat likely played a significant role in expanding cranial capacity – developing a larger brain – during human evolution. Animal resources provide a highly concentrated source of calories and are rich in essential nutrients, minerals and vitamins that are crucial for supporting a large brain. ” said geochemist Tina Lüdecke of the Max Planck Institute for Chemistry in Germany and the University of the Witwatersrand in South Africa, lead author of the study published Thursday in the journal Science.

“Our data challenge the assumption that meat was a crucial dietary component for Australopithecus, although some specimens were found in association with stone tools and bones with cut marks,” said Lüdecke.

The results suggest that meat consumption was a later development, perhaps by subsequent populations of the various distinct Australopithecus species or by other species in the human evolutionary line, collectively called hominins. Australopithecus inhabited eastern and southern Africa about 4.2 to 1.9 million years ago. Our species Homo sapiens appeared around 300,000 years ago.

The seven people examined were vegetarians.

“While occasional meat consumption is plausible, similar to modern non-human primates such as chimpanzees and baboons, our data suggest a diet consisting primarily of plant resources,” Lüdecke said.

This could have included looking for fruits, tree leaves and certain flowering plants in the savanna landscape, said Lüdecke.

Australopithecus had ape-like facial proportions and a brain about a third the size of our species, as well as relatively long arms with curved fingers that were good for tree climbing. Australopithecus stood on two legs and walked upright.

“Australopithecus provides crucial insights into the evolution of bipedal locomotion and early tool use. While their brains were smaller than ours, their relative brain size was slightly larger than that of modern chimpanzees,” Lüdecke said.

The most famous Australopithecus fossil, nicknamed “Lucy,” was discovered in Ethiopia in 1974 and is about 3.2 million years old. Lucy, probably female, was about three feet tall. Males would have been slightly larger.

Lucy was a member of the species Australopithecus afarensis. The seven individuals in the study are likely members of the closely related species Australopithecus africanus.

The chemistry of the food consumed by a person is incorporated into tissues, including hard parts such as tooth enamel, which promote fossilization. The researchers analyzed seven fossilized molars found in Sterkfontein Cave near Johannesburg, part of South Africa’s “Cradle of Humankind” area known for producing early hominin fossils.

The ratio of two different forms – isotopes – of the element nitrogen in the Australopithecus teeth was more consistent with fossils of herbivorous animals in the same ecosystem, such as antelopes, than with carnivorous animals such as hyenas, leopards and saber-toothed cats.

Some of the earliest evidence of possible meat consumption among hominins includes animal bones with cut marks dated to 3.4 million years ago in Ethiopia. Whether this involves the slaughter of meat is controversial.

The finding that Australopithecus, with a smaller brain than later hominins, “did not consume significant amounts of mammalian meat is consistent with the hypothesis that dietary change played a role in brain expansion,” said study co-author Alfredo Martínez- García, head of the study at the Organic Isotope Geochemistry Laboratory of the Max Planck Institute for Chemistry.

“If we had found that Australopithecus consumed significant amounts of meat, we would have concluded that the subsequent increase in skull volume in other hominin species was not due to the onset of meat consumption,” Martínez-García added.

Meat consumption may also have contributed to increased body size, reduced gut size, social complexity, and tool use in hominins.

“The crucial questions remain: Who first started eating meat, when did it start, and when did it become a resource significant enough to drive morphological adaptations?” Lüdecke said.

(Reporting by Will Dunham in Washington, Editing by Rosalba O’Brien)