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Human mtDNA Diversity Before Migration Out of Africa

image Yesterday, a very interesting paper was published in the American Journal of Human Genetics by the Genographic Project Consortium entitled “The Dawn of Human Matrilineal Diversity.” The results of the study, which examined the 624 mtDNA genomes from sub-saharan Haplogroup L lineages, suggests that humanity once split into two small groups with one group in eastern Africa and the other in southern Africa, and that humanity bottlenecked into a relatively small number of individuals (as few as 2,000 based on results from a previous study). Note, as always, that these are hypotheses based upon the results of this and other studies, and will require further research to support or refute.

Two mtDNA Branches

The human mtDNA tree has two main branches, the L0 branch which includes individuals concentrated in southern and eastern Africa, and the L1’2’3’4’5’6′ branch (aka the L1’5 branch), which includes the entire remainder of humanity including non-Africans (see the figure to the left). Based upon the analysis of the 624 genomes, the researchers hypothesized that the L0 and L1’5 branches diverged into two small populations around 140,000 to 210,000 years ago, with one group settling in eastern Africa (the L1’5 branch) and the other settling in southern Africa (the L0 branch). Interestingly, the results also suggest that there was little to no intermingling of these branches for the next 50,000 to 100,000 years!

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34

Famous DNA Review, Part III – Niall of the Nine Hostages

ireland2.jpgAs many as 3 million men worldwide might be directly descended from a single Irish warlord named Niall of the Nine Hostages who was the High King at Tara from 379 to 405.

In February 2006, researchers at Trinity College in Dublin released a paper that studied that Y chromosome signature of men throughout Ireland. They found that 8% of men sampled had the same Y chromosome, with a cluster in the northwest where fully 21% of men carried the signature chromosome (which fell into Haplogroup R1b1c7). The article appeared in The American Journal of Human Genetics and was titled “A Y-Chromosome Signature of Hegemony in Gaelic Ireland.”

The researchers looked at 17 STR markers on Irish Y chromosomes to determine the relatedness of samples they had obtained. They found that there was a strong association between the most common signature and surnames that were related to the most significant dynasty of early medieval Ireland – the Uí Néill. Some of the surnames included (O’)Gallacher, Boyle, O Doherty, O’Connor, Cannon, Bradley, O’Reilly, Flynn, (Mc)Kee, Devlin, Donnelly, Egan, Gormley, Hynes, McCaul, McGovern, McLoughlin, McManus, McMenamin, Molloy, O’Kane, O’Rourke and Quinn (list from Oxford Ancestors). Of course there were no surnames at the time of the earliest Uí Néill dynasty, but when the Irish took surnames around 1,000 A.D., many chose names that were associated with Uí Néill dynasties.

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7

Daughters of Eve in DNA Paintings

Artist Ulla Plougmand-Turner has created paintings of The Seven Daughters of Eve using paint that contains reconstructed ancient DNA manufactured by Oxford Ancestors.

Most genetic genealogists are very familiar with Bryan Sykes’ Seven Daughters of Eve, the 7 “clan mothers” (Ursula, Xenia, Helena, Velda, Tara, Katrine, and Jasmine) from whom the majority of Europeans are believed to obtain their mitochondrial DNA.Note that there are many more “clan mothers” located throughout the world – I, for instance, am descended from clan Aiyana.

The exhibition was commissioned by Professor Bryan Sykes, the head of Human Genetics at Oxford University and the founder of Oxford Ancestors.Prof. Sykes met Ms. Plougmand-Turner by chance when he was taking DNA samples from villagers at Longleat.

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6

Famous DNA Review, Part II – Genghis Khan

In 2003, researchers from around the world released a paper that suggested that 8% of all Mongolian males have a common Y chromosome because they are the descendants of Genghis Khan (See “The Genetic Legacy of the Mongols,” 2003, Zerjal, et. al., American Journal of Human Genetics, 72: 717-721).The researchers examined the Y chromosome variability of over 2000 people from different regions in Asia and discovered a grouping of closely related lines.The cluster is believed to have originated about 1,000 years ago in Mongolia and its distribution coincides with the boundaries of the Mongol Empire.

Genghis Khan’s empire (he ruled from 1206 – 1227) stretched across Asia from the Pacific Ocean to the Caspian Sea and was reportedly extremely prolific.Khan’s son Tushi had as many as 40 sons.His grandson Kublai Khan is reported to have had as many as 22 sons, and perhaps many more.Together this family may have as many as 16 million descendants alive in Asia today.It is extremely important to note that until DNA can be extracted from Khan’s bones (which have never been found), there is no definitive proof that this Y chromosome cluster is actually descended from Genghis Khan.

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Are aboriginal Australians and New Guineans the modern-day descendants of the extinct species Homo erectus?

Some scientists have hypothesized that Australian aboriginals received a portion of their DNA from an ancient hominid species called Homo erectus, which for a short time was contemporaneous with modern man. A recent study published in PNAS (Proceedings of the National Academy of the Sciences) set out to answer this question by analyzing mtDNA and Y-chromosome samples from aboriginals.

A total of 172 mtDNA and 522 Y-chromosome previously published and new sequences from aboriginal Australians and New Guineans were analyzed for mtDNA and Y-chromosome variation and were compared to the current world haplogroup tree. All of the mtDNA sequences were members of the M and N founder branches, and all of the Y-chromosome sequences fell into the C and F founder branches.

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4

Who Crossed the Bering Land Bridge?

dna2.jpgHow many founding Asian groups braved their way across the Bering land bridge during those frigid Pleistocene ice ages?Was it a single wave of people who later developed into the three distinct linguistic and cultural groups that populated the Americas, or were there multiple waves of people each with their own language and culture? Or was it some mix of the two?The issue has been and continues to be a topic of debate.

Linguistic studies of the Na-dene, Aleut-Eskimo, and Amerind language groups suggested that there were three waves across the land bridge, one for each language group.Recent genetic research, however, has suggested that there was only a single wave of founding groups into the Americas. (Read a free online review here).

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