| By Paul Rincon |
Researchers found a very high amount of genetic variation, or diversity, between the mitochondrial DNA of different individuals in these populations.
Mitochondrial DNA is passed down exclusively through the maternal line. The longer a population has existed, the more variation accumulates in its DNA lineages.
"They are showing really deep, old lineages with lots of diversity. They appear to be the oldest lineages identified in Africa to date," said Dr Sarah Tishkoff, of the University of Maryland, US, who led the research.
Great resource
The so-called African Eve represents the ancestral mitochondrial genome that gave rise to all the different types seen in people today.
Several of the ethnic groups sampled in the study also live in countries surrounding Tanzania.
"It's entirely consistent with what we expected," said Dr Spencer Wells, a geneticist and author. "All the evidence is pointing to East Africa as the cradle of humanity."
Dr Wells added that the data ties in well with archaeological evidence of a long occupation of East Africa by modern humans and hominids.
But Professor Ulf Gyllensten, a molecular biologist at the University of Uppsala, Sweden, was cautious about claims that the oldest DNA lineages were confined to East Africa.
"I wouldn't be surprised if Dr Tishkoff has found old lineages there, but I think we're just skimming the surface," he said.
"Too little research has been done in Africa to get a clear picture. I don't know why, because it's clear there is a great resource of genetic diversity there," added Professor Gyllensten.
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