MITOCHONDRIAL EVE

In the field of human genetics, Mitochondrial Eve refers to the matrilineal "MRCA" (most recent common ancestor). In other words, she was the woman from whom all living humans today descend, on their mother's side, and through the mothers of those mothers and so on, back until all lines converge on one person. Because all mitochondrial DNA (mtDNA) is generally passed from mother to offspring without recombination, all mitochondrial DNA (mtDNA) in every living person is directly descended from hers by definition.Mitochondrial Eve lived much earlier than the out of Africa migration that is thought to have occurred between 95,000 to 45,000 BP.^[4]

The dating for 'Eve' was a blow to the multiregional hypothesis, and a boost to the hypothesis that modern humans originated relatively recently in Africa and spread from there, replacing more "archaic" human populations such as Neanderthals. As a result, the latter hypothesis is now the dominant one.

As tribes began to migrate to different parts of Africa, or even to different parts of the world by the Land Bridge, but water....they had to adjust to their different environments, climates, etc. Over time and generations, the people began to adjust and their appearances began to change - determined first by their environment......For example, those who stayed in certain parts of African retained dark skin to help protect them from the long, hot sunny days, and very warm climate. Those who arrived in Europe or further north to places of colder climate - lost much of their melanin - so over time these peoples skin became very light. Their hair long ad straight to help insulate them from the colder climate. The variations go on!

Of course as our world has become smaller due to airplanes, ships, etc., generations are becoming more of a melting pot...but there are still lingering and specific phenotypes and genotypes that can identify people from different continents, and different countries.
Here are some photographs of different peoples who have evolved from Mitochondrial Eve:

NOTE: Excerpts of The definition of MITOCHONDRIAL EVE retrieved from

http://en.wikipedia.org/wiki/Mitochondrial_Eve