Design of Life

Was humanity separated into small groups for many thousands of years? Recently, some researchers examining human mitochondrial DNA (the DNA in the power plants of our cells, which is not the same as the DNA in our 46 chromosomes) concluded that

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.

Based on the study of 600 compete genomes of Africans, they believe that massive droughts between 90, 000 and 135, 000 years ago split humans into two separate groups, or "long lost sisters".

Dr. Spencer Wells, director of the Genographic Project and Explorer-in-Residence at the National Geographic Society, said, "This new study illustrates the extraordinary power of genetics to reveal insights into some of the key events in our species' 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 also believed that the human race was reduced in size to about 2000 people, and that by about 70,000 years ago, we banded together and survived. As The Jerusalem Post tells it,

The genetic split in Africa resulted in distinct populations that lived in isolation for as much as 100,000 years, the scientists say. At the time of the split - some 150,000 years ago - our species, Homo sapiens, was still confined to the African continent.
On one side of this divide were the mitochondrial lineages now found predominantly in East and West Africa, and all maternal lineages found outside Africa.
On the other side of the divide are lineages predominantly found in the Khoi and San (Khoisan) hunter-gatherer people of southern Africa.
This could have been caused by arid conditions driving a wedge between humans in eastern and southern Africa. It would be the longest period for which modern human populations have been isolated from one another.
The isolated African groups started to meet up again with each other about 40,000 years ago, during the African Late Stone Age, and then grew in numbers and moved to an expanding area. Many archeologists believe this era heralded the beginning of fully modern human behavior, including abstract thought and complex spoken language.
Other researchers have hypothesized that during the initial isolation, about 70,000 years ago, Homo sapiens was almost wiped out, with the world population numbering as low as 2,000 people. But they banded together and survived.

The researchers studied blood and cheek cells stored in labs across the globe, to look at the mitochondrial DNA of 600 people of known African origin from a variety of nations.

The next research paper may argue a different thesis, so it's best to keep an open mind. Meanwhile, this paper, "The Dawn of Human Matrilineal Diversity" by Doron Behal et al., can be read here (American Journal of Human Genetics)