FIGURE 1. A hominin taxonomy.

Species are ordered according to the period of their fossil record and, left to right, according to their resemblance to modern humans: those with large brains, small chewing teeth and jaws similar to those of Homo sapiens are found to the left, those with large chewing teeth and jaws to the right. Australopithecus afarensis, an infant female specimen of which has been found in Dikika, Ethiopia^{1, 2}, lived between 4 million and 3 million years ago. Its small brain is not much larger than that of a chimpanzee, but its dentition has features akin to those found in more modern hominins.