The human race was divided into two separate groups within Africa for as much as half of its existence, says a Tel Aviv University mathematician. Climate change, reduction in populations and harsh conditions may have caused and maintained the separation.

Dr. Saharon Rosset, from the School of Mathematical Sciences at Tel Aviv University, worked with team leader Doron Behar from the Rambam Medical Center to analyze African DNA. Their goal was to study obscure population patterns from hundreds of thousands of years ago.

Rosset, who crunched numbers and did the essential statistical analysis for the National Geographic Society’s Genographic Project, said the team was trying to understand the timing and dynamics of the split into at least two separate groups.

“We wanted to look into the ancient history of our species. How did we live throughout most of our existence as a species? Did we live as one — or were we fractured into small groups? Until now, it wasn’t really clear,” says Rosset.

A Picture of the Ancient Past

Researchers believe that about 60,000 years ago, modern humans started their epic journeys to populate the world. This time period has been the primary focus of anthropological genetic research. However, relatively little is known about the demographic history of our species over the previous 140,000 years in Africa.

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Human beings may have had a brush with extinction 70,000 years ago, an extensive genetic study suggests. The human population at that time was reduced to small isolated groups in Africa, apparently because of drought, according to an analysis released Thursday.

The report notes that a separate study by researchers at Stanford University estimated the number of early humans may have shrunk as low as 2,000 before numbers began to expand again in the early Stone Age.

“This study illustrates the extraordinary power of genetics to reveal insights into some of the key events in our species’ history,” Spencer Wells, National Geographic Society explorer in residence, said in a statement.

“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.”

Previous studies using mitochondrial DNA — which is passed down through mothers — have traced modern humans to a single “mitochondrial Eve,” who lived in Africa about 200,000 years ago.

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Nearly all of today’s Native Americans in North, Central and South America can trace part of their ancestry to six women whose descendants immigrated around 20,000 years ago, a DNA study suggests. Furthermore, they passed their mtDNA to about 95 percent of Native Americans, researchers said.

The women lived between 18,000 and 21,000 years ago, though not necessarily at exactly the same time, he said. The work was published this week by the journal PLoS One. Perego is from the Sorenson Molecular Genealogy Foundation in Salt Lake City and the University of Pavia in Italy.

The researchers created a “family tree” that traces the different mitochondrial DNA lineages found in today’s Native Americans. By noting mutations in each branch and applying a formula for how often such mutations arise, they calculated how old each branch was. That indicated when each branch arose in a single woman.

The six “founding mothers” apparently did not live in Asia because the DNA signatures they left behind aren’t found there, Perego said. They probably lived in Beringia, the now-submerged land bridge that stetched to North America, he said. Connie Mulligan of the University of Florida, an anthropolgist who studies the colonization of the Americas but didn’t participate in the new work, said it’s not surprising to trace the mitochondrial DNA to six women. “It’s an OK number to start with right now,” but further work may change it slightly, she said. That finding doesn’t answer the bigger questions of where those women lived, or of how many people left Beringia to colonize the Americas, she said Thursday.

The estimate for when the women lived is open to question because it’s not clear whether the researchers properly accounted for differing mutation rates in mitochondrial DNA, she said. Further work could change the estimate, “possibly dramatically,” she said.
from Daily Times

MITOMAP, the human mitochondrial genome database, has recently published a paper in Nucleic Acids Research announcing the completion of a full human mtDNA phylogenetic tree. [read full article]

This tree, available here (in pdf) was constructed from 2959 mtDNA coding region sequences. I find it hard to deal with because of the wide format. It lists mutations and the study that identified each particular sequence, the tree labels each mutation as a substitution mutation, a silent mutation, a tRNA or rRNA mutation, a mutation in the noncoding region, or a pathological mutation. MitoMap also provides another valuable tool, tables of mtDNA polymorphisms with source information.

The tree will potentially be very useful to both researchers and genetic genealogists by providing a quick and easy way to characterize new sequences. Anyone interested in learning more about their haplogroup or how their haplogroup fits into the human mtDNA tree will find the new mtDNA phylogenetic tree extremely informative.

Note: there is another tree view that I prefer located HERE

From Cincinnati - In their quest to determine their ancestral origins, many family historians are turning to the power of science - in the form of DNA testing - to help them decode the mysteries of their unique genetic makeup.

Though certainly not a substitute for traditional genealogical research methods, the appeal of DNA testing has been further popularized by high-profile figures such as Oprah Winfrey, whose DNA analysis-augmented family history was recently broadcast in a segment entitled “Oprah’s Roots” on the PBS series “African American Lives.”

Though debates about the validity and reliability of genetic testing results - and what they reveal about your ancestry - continue, many curious family historians are intrigued by the clues which may be discovered by submitting a painless sampling of inner cheek cells to one or several of the many DNA testing companies located both here and abroad.

As genetic genealogy expert Megan Smolenyak, author of “Trace Your Roots with DNA: Using Genetic Tests to Explore Your Family Tree,” notes within her introduction, there are two types of DNA that follow a straight line rather than a meandering path, mitochondrial DNA, or mtDNA (which is passed by a mother to her children, male and female) and Y-DNA (which is passed from father to son).

Y-DNA and mtDNA tests typically yield information about a small section of your ancestral pool, while BioGeographical Ancestry tests - which check the genetic markers present in autosomal, or non-sex determining chromosomes - can yield estimates on your family’s geographic origins.

Those interested in learning more about the possibilities of DNA testing as a genealogical tool should consider attending a program being offered at the Erlanger branch of the Kenton County Public Library, entitled “Genetic Genealogy.” The program, which is scheduled for 7 p.m. Monday, Oct. 8, will feature a guest speaker from the International Society of Genetic Genealogy. The program is free, but registration is required.

Those interested in attending may register either by calling the Erlanger branch at (859) 962-4000, ext. 4107, or by visiting the library’s Web site, www.kentonlibrary.org.

Genealogy tips are provided by the Kentucky history staff of the Kenton County Public Library. This tip was provided by Jan Mueller. Contact the library’s local history department by calling (859) 962-4085 or via e-mail at history@kentonlibrary.org. The library’s genealogy Web site can be found at http://www.kentonlibrary.org/genealogy.