protein electrophoresis) on the divergence of humans and chimpanzees, and showed that all methods agreed that the two species were >99% similar. Given the large organismal differences between the two species in the absence of large genetic differences, King and Wilson proposed that it was not structural gene differences that were responsible for species differences, but gene regulation of those differences, that is, the timing and manner in which near-identical gene products are assembled during embryology and development. In combination with the "molecular clock" hypothesis, this contrasted sharply with the accepted view that larger or smaller organismal differences were due to large or smaller amounts of genetic divergence. In the early 1980s, Wilson further disturbed and refined traditional anthropological thinking by his work with PhD students Rebecca Cann and Mark Stoneking on the so-called "Mitochondrial Eve" hypothesis. In his efforts to identify informative genetic markers for tracking human evolutionary history, he focused on mitochondrial DNA (mtDNA) – genes that are found in mitochondria organelles in the cytoplasm of the cell outside the nucleus. Because of its location in the cytoplasm, mtDNA is passed exclusively from mother to child, the father making no contribution, and in the absence of genetic recombination defines female lineages over evolutionary timescales. Because it also mutates rapidly, it is possible to measure the small genetic differences among individual within species and between closely related species by restriction endonuclease gene mapping. Wilson, Cann, and Stoneking measured differences among many individuals from different human continental groups, and found that humans from Africa showed the greatest inter-individual differences, consistent with an African origin of the human species (the Recent African origin of modern humans or "Out of Africa" hypothesis). The data further indicated that all living humans shared a common maternal ancestor, who lived in Africa only a few hundreds of thousands of years ago. This common ancestor became widely known in the media and popular culture as the Mitochondrial Eve. This had the unfortunate and erroneous implication that only a single female lived at that time, when in fact the occurrence of a coalescent ancestor is a necessary consequence of population genetic theory, and the Mitochondrial Eve would have been only one of many humans (male and female) alive at that time. This finding was, like his earlier results, not readily accepted by anthropologists. The conventional hypothesis had been that various human continental groups had evolved from diverse