Researcher rejects 'out of Africa' theory By Damon Shorter An ANU geneticist has created a stir among human evolutionists by claiming crucial evidence supporting the most widely-held theory of human origins may be wrong. At stake is the "out of Africa" evolutionary model - supported by most palaeontologists - which claims the first Homo sapiens evolved in Africa some 100,000 years ago, before quickly spreading to all corners of the earth, wiping out more primitive humans such as Neanderthals and Homo erectus in their path. The alternative theory - less popular in archaeological circles - is the "multi-regional model", which suggests Homo sapiens evolved progressively from earlier humans over a much longer time scale on the different continents. Speaking at the Horizons of Science forum in Sydney last month, Dr Simon Easteal, from the Human Genetics Group at the John Curtin School of Medical Research, said the "out of Africa" model may be a huge scientific mistake. Most genetic evidence for the model comes from comparisons of DNA from different human populations around the world. Researchers have found a remarkable genetic similarity between races, which has been interpreted as evidence of a recent common African ancestor. Yet as Dr Easteal pointed out, there is more than one type of DNA in the body. The DNA most commonly used for genetic comparison is the mitochondrial DNA, a small part of the human genetic code distinct from the rest of the cell's genetic material. And although the mitochondrial DNA is very similar between human racial groups, the rest of our DNA is not, he told the forum. The implication, Dr Easteal said, is not that all modern people shared an ancestor 100,000 years ago (the out of Africa interpretation), but rather, a new sort of mitochondrion evolved at this time and spread through all populations in the world. The idea makes sense when the role of the mitochondria in the body is taken into account. Mitochondria generate energy in cells. In order to evolve a bigger brain, our ancestors needed to make more energy (the average human brain uses about 24 watts). Dr Easteal theorised that a favourable mutation created an "improved" mitochondrion in Africa around 100,000 years ago which spread through existing populations and brought about the evolution of Homo sapiens. Dr Colin Groves, an authority on human evolution from the Department of Archaeology and Anthropology in the Faculties, said Easteal's argument was "an interesting idea" but pointed to substantial fossil evidence supporting the out of Africa model. He also said that massive interbreeding must have occurred between different human races for the new mitochondria to spread so quickly.