Researchers studying isotopic ratios in these ancient teeth gained insight into the diets of our ancestors.
The food preferences of two early human ancestors and another competing species have been elucidated by mass spectrometric analysis of their tooth enamel (Nature, DOI: 10.1038/nature11349). An international team led by Vincent Balter of École Normale Supérieure in Lyon, France, analyzed calcium, strontium, and barium isotopes in fossilized molars. The researchers discovered that two species of Australopithecus, a bipedal ancestor of the Homo lineage, and a concurrent competitor, Paranthropus, had much more diverse diets than their successors. Although all three hominins ranged over a similar-sized territory, Australopithecus ate a variety of both plants and meats before dying out 2 million years ago. On the other hand, the isotopic ratios from subsequent Homo ancestors show that modern human forebears had a predilection for meat—for example, low Ba/Ca levels are characteristic in carnivores, whereas higher Ba/Ca levels are characteristic in herbivores. The competing Paranthropus species preferred a more plant-based diet, the researchers note, which may have “contributed to its demise because it was unable to adapt to the changing environmental conditions that took place approximately 1 million years ago.”