DNA Molecule

A schematic of a DNA molecule. (Public Domain image from Wikimedia commons.)

Every human being alive today has a maternal line, daughter from mother, that traces back to the same woman, who lived in Africa some 180,000 years ago. This comes from analyzing the mitochondrial DNA of people all over the world. There were small changes, mutations, of this mDNA over time, and these can be used to trace the branches of this woman’s descendants.

The first important mutation I carry is called L3. Although L3 is found today in Africa, it is thought to be the branch of the first woman’s descendants that first moved out of Africa, and is found today all over the world. This mutation is thought to have originated somewhere in East Africa some 70,000 years ago.

The next important mutation is called N, and it probably occurred in East Africa or western Asia about 60,000 years ago. This woman’s descendants probably traveled down the Nile and crossed into the modern Levant. They are very widespread today, but most important in the Near East and Europe. Chances are they were still very darkly pigmented, as they lived in a very sunny area. (Light coloration is thought to be an adaptation to a need to let sunlight through the skin to produce vitamin D.)

A mutation in a woman of the N group, probably about 55,000 years ago in West Asia, is called R. Apparently the descendants with the R mutation stayed with the parent N group, and both groups moved together through Turkey, the Middle East, and southern Russia.

A subgroup of R, called RO, occurred about 41,000 years ago somewhere in West Asia. This group produced the Cro-Magnons in Europe, but is most frequent today in Arabia and also moved into the Indus Valley.

The next important mutation in my female line was called HV. Like the M and RO groups, it arose in Western Asia. The Palestinian area is not only a political hotbed today, it is the origin of a large part of the “white” race. This mutation occurred relatively recently, around 22,000 years ago.

The next mutation is a little confusing, as the mutation to H is assumed to have occurred about 28,000 years ago, also in West Asia. It should be pointed out that the age estimates can be significantly skewed by such events as population bottlenecks. H is in any event the dominant maternal genotype in Western Europe.

The mutation to H1 is assumed to have take place a mere 18,000 years ago, still in West Asia. This line is again most common today in Western Europe. Some of these individuals may have been light skinned, in an evolutionary ploy to avoid rickets. I might point out that it is now recognized that at least two separate mutations to light skin have occurred, one in the West and one in Eastern Asia. Both help with the production of Vitamin D, but only the Western form gives an increased likelihood of skin cancer.

I have one final mutation, of undetermined age, called HB. This one is fairly rare. It may have arisen in Central Asia and runs between 1 and 2 percent of modern Europeans.

Overall, my ancestors in female line seem to have done a lot of traveling!

(The information above was taken from my results at the Genographic Project website. What does your mitochondrial DNA show?)

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