Evolution

Mitochondrial Dna and Human Evolution in Search of Eve



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There have been many studies done on population genetics and human evolution and migration in the past 20 or so years. Tracing back the early human population's demographic history all the way to the time before our ancestors moved out of Africa has been one of modern science's more intriguing and exciting feats to date. The search for "Mitochondrial Eve", from the first publication by Cann et al. in 1987 to Gonder et al. in 2007 and the Genographic Society in 2008, dates humanity's most recent common matrilinear ancestor to a woman who lived around 8,000 generations or 200,000 years ago in Africa.

Mitochondrial DNA (mtDNA) is special in the same way the Y-chromosome is also special. The Y-chromosome is found can be passed only from father to son and does not get recombined with the mother's genes, whereas the mtDNA is different from nuclear DNA since it can be found outside the cell's nucleus and can be passed down from the mother to her offspring. mtDNA also does not get recombined and mutates at a faster pace than its nuclear counterpart.

But what is the trick in tracking human evolution from mtDNA? Haplogroups are what we call a group that share a similar set of Single Nucleotide Polymorphisms (SNPs) that are statistically associated and also share a common ancestor. Researchers use these SNPs in the mtDNA as pegs to an approximated time. By doing comparisons of samples and known pegs, they can more or less recreate the routes of one's female ancestors. Because of these special properties, the origins of mtDNA are statistically more sound thus making it more suitable for constructing these molecular phylogenies.

Around 140,000 years after Mitochondrial Eve, 60,000 years ago, a wave of human migration out of Africa started. We know so little about what happened before this great migration, and finding out how humans lived during such a long period of time is the primary focus of anthropological geneticists today.

Studies done by the Genographic project show evidence that as early as 150,000 years ago humans already began moving around the African continent, splitting the population into two separate groups. One group settled in Africa's southern region and another group in the eastern part of the continent. They reunited again as one population after 100,000 years. A series of severe droughts might have contributed to this long split in populations when humans numbered only about 2,000 individuals. Only after an expansion of the population 70,000 years ago did the great migrations slowly begin.

So much data about human evolution and history is continually being uncovered today by studying the changes of mtDNA over time. Anyone can access the latest developments on The Genographic Project's website. You can even participate in the study by contributing your own DNA samples collected via the buccal swab that comes with the participation kit that you need to order. They test the participant's mtDNA and Y-chromosome as well for men. After they have done the testing, participants can then get a glimpse of interesting facts about their ancestry along the mtDNA line (and Y-chromosome line for males). Migration paths taken by ancestors are also shown in the profile and will then be included in a particular branch of humanity's big family tree.

I end this article by quoting the Director of the Genographic Project, Dr. Spencer Wells: "This new study released today illustrates the extraordinary power of genetics to reveal insights into some of the key events in our specie's history. Tiny bands of early humans, forced apart by harsh environmental conditions, coming back from the brink to reunite and populate the world. Truly an epic drama, written in our DNA." It is indeed a great privilege to live at a time when we can know so much about humanity and the deep personal history coded in the stuff that make up the person we see in the mirror. The years of extensive research on mtDNA and human evolution have uncovered great mysteries on the diversity in the cultures and races that we see today, and at the same time our species unity through the our origins in the Mitochondrial Eve.

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