An ancient skull and jawbone discovered in Africa suggest that Homo erectus and Homo habilis lived side by side, feeding on different sources over a million years ago
An ancient skull and jawbone, originating from the early branches of the human family tree - Homo erectus and Homo habilis - indicate that the ancestors of humans lived near each other for about half a million years, researchers revealed last Wednesday.
The fossils, discovered in East Africa, challenge the assumption that humans evolved in stages, like dominoes, from Homo habilis to Homo erectus, to Homo sapiens, the modern man. "The conventional view is that Abilis evolved slowly from Eractus," says Susan Anton, professor of anthropology at New York University. Now we discovered that this was not the case and that they both lived at the same time."
The research, which was published in the journal Nature, was carried out by nine scientists, including Anton, paleontologist Maeve Leakey and her daughter Louise Leakey, both researchers at the National Geographic Society, and Fred Spoor at University College London. The two fossils are west of Lake Torkema in Kenya, as part of a research project funded by the National Museums Authority of Kenya.
The proximity of the fossils suggests that the two species used different food sources when they lived in close proximity and behaved differently from each other - otherwise they would have become extinct. "There is only a two-three minute walk between them," says Patrick Gatogo, a doctoral student from the University of Utah, who assisted in the study of the geological layers in the area. "There must have been an interaction between the two strains."
A 1.55 million year old skull
The second fossil, found in the same area in northern Kenya, is a well-preserved skull of Homo erectus, which has been dated to about 1.55 million years old. The fossil is amazing due to its size - it is the smallest Homo erectus skull found to date, and it paints a different picture of the species, suggesting that the variety was wider than scientists thought.
Reduced differences in size between the sexes is considered a trait acquired during human evolution. One possible meaning of the diversity is that, similar to gorillas, whose males have much larger skulls than females, Homo erectus exhibited sexual dimorphism in a primitive version, the researchers believe.
"This defines Homo erectus as a little less similar to us," explains Anton simply. Researcher Fred Spoor says that all available evidence suggests that Homo sapiens evolved from Homo erectus, a process that occurred in Africa more than a million years ago. Also, he says that it is likely that the two varieties had a common ancestor, who lived in Africa 2-3 million years ago.
