'Mitochondrial Eve': Mother of All Humans Lived 200,000 Years Ago
ScienceDaily (Aug. 17, 2010) — The most robust statistical examination to date of our species' genetic links to "mitochondrial Eve" -- the maternal ancestor of all living humans -- confirms that she lived about 200,000 years ago. The Rice University study was based on a side-by-side comparison of 10 human genetic models that each aim to determine when Eve lived using a very different set of assumptions about the way humans migrated, expanded and spread across Earth.
Artist's cross section of a mitochondrion. (Credit: iStockphoto/David Marchal)
The research is available online in the journal Theoretical Population Biology.
"Our findings underscore the importance of taking into account the random nature of population processes like growth and extinction," said study co-author Marek Kimmel, professor of statistics at Rice. "Classical, deterministic models, including several that have previously been applied to the dating of mitochondrial Eve, do not fully account for these random processes."
The quest to date mitochondrial Eve (mtEve) is an example of the way scientists probe the genetic past to learn more about mutation, selection and other genetic processes that play key roles in disease.
"This is why we are interested in patterns of genetic variability in general," Kimmel said. "They are very important for medicine."
For example, the way scientists attempt to date mtEve relies on modern genetic techniques. Genetic profiles of random blood donors are compared, and based upon the likenesses and differences between particular genes, scientists can assign a number that describes the degree to which any two donors are related to one another.
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doi:10.1016/j.tpb.2010.06.001
Alternatives to the Wright–Fisher model: The robustness of mitochondrial Eve dating
Krzysztof A. Cyrana and Marek Kimmelb, c, ,
a Institute of Informatics, Silesian University of Technology, Gliwice, Poland
b Department of Statistics, Rice University, Houston, TX, United States
c Systems Engineering Group, Silesian University of Technology, Gliwice, Poland
Received 18 March 2009.
Available online 19 June 2010.
Abstract
Methods of calculating the distributions of the time to coalescence depend on the underlying model of population demography. In particular, the models assuming deterministic evolution of population size may not be applicable to populations evolving stochastically. Therefore the study of coalescence models involving stochastic demography is important for applications. One interesting approach which includes stochasticity is the O’Connell limit theory of genealogy in branching processes. Our paper explores how many generations are needed for the limiting distributions of O’Connell to become adequate approximations of exact distributions. We perform extensive simulations of slightly supercritical branching processes and compare the results to the O’Connell limits. Coalescent computations under the Wright–Fisher model are compared with limiting O’Connell results and with full genealogy-based predictions. These results are used to estimate the age of the so-called mitochondrial Eve, i.e., the root of the mitochondrial polymorphisms of the modern humans based on the DNA from humans and Neanderthal fossils.
Keywords: Coalescence distribution; Branching processes genealogy; Wright–Fisher model; O’Connell model; Computer simulations; MtEve dating; Neanderthal mtDNA
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