Age of "Mitochondrial Eve" Confirmed: 200,000 Years Old

Rice University researchers have conducted what they describe as the most "robust" statistical comparison of 10 human genetic models to confirm the age of the maternal ancestor of all living humans.

U.S. Dept. of Health and Human Services/National Institutes of Health

"Mitochondrial Eve," as she is called, lived about 200,000 years ago - probably somewhere in Africa, according to Marek Kimmel, professor of statistics at Rice and co-author of a study in the journal Theoretical Population Biology. The existence of a common maternal ancestor was first discovered in 1987.

"These are modern humans," Kimmel said in an interview with CBSNews.com. "They go back 200,000 years but physically, they are modern. Regarding their brains, the brain case is the same as ours and the superficial appearance of their brains, judging from the imprint on their skulls, is similar to ours."

The research was carried out using mitochondrial genomes to measure modern humans' genetic links back to "Mitochondrial Eve" because mitochondria are inherited only through females. This makes any examination of inheritance patterns much simpler - which is why it's commonly used. (The male counterpart would be the "Y" chromosome.)

Kimmel and his co-author Krzystof Cyran were able to infer Eve's age from certain patters which annotate hmans' genetic past. Kimmel noted that mutations accumulate over time and therefore, people descending from a common ancestor will have increasingly different DNA.

"So, you can use the divergence between different peoples' genomes as a sort of clock. If you know the mutation rate, by counting the click rates (of the clock,) you can infer the time," he said. "Of course there's lot of mathematics involved. The complicating factor is that all this occurs in populations and not all will survive....and to calibrate the clock, you have to take into account the changing population size.

"The encouraging message of this paper is basically that within a certain set of methods, you get roughly same answer," he added.

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