The human population arose from a single migration out of Africa 55000 years ago
Most researchers agree that mankind spread out of Africa starting about 50,000 years ago, quickly establishing Stone Age cultures throughout Europe, Asia and Australia.
But a minority have argued, using skull data, that divergent populations evolved independently in different areas.
The genetic evidence has always strongly supported the single origin theory, and now results from a study of more than 6,000 skulls held around the world in academic collections supports this case.
According to both genetic and fossil evidence, archaic Homo sapiens evolved to anatomically modern humans solely in Africa, between 200,000 and 100,000 years ago, with members of one branch leaving Africa by 60,000 years ago. It is believed that humans originated from Ethiopia, then migrating into the Near East.
Scientists believe that only a few people left Africa in a single migration that went on to populate the rest of the world.It has been estimated that from a population of 2,000 to 5,000 in Africa, only a small group of possibly 150 people crossed the Red Sea. It is beliveed that there may have been another migrtion into India. Another group of migrants with followed the Nile from East Africa, heading northwards and crossing into Asia through the
From the Near East, these populations spread east to
Humans then began migrating out of Africa in successive waves, starting approximately 100,000 years or 5000 generations ago. Now that scientists have mapped the human genome, they are homing in on when each wave began their outward bound journey and where they migrated to. So far they have confirmed that everyone on the entire planet, even the 1.3 billion Chinese, have a common ancestor back in Africa.
So where did the 10,000+ shades of paler brown, beige, pink, white come from? As humans migrated out of Africa, why did dark skinned people start losing the genetics Powerball Lottery to their paler kin? Lower UV levels in the sunlight of the more northern latitudes meant a dark skinned individual's body could not produce enough Vitamin D. What scientists now believe is that everyone started out with dark skin in the first place because it is protective against absorbing too much Vitamin D, which is toxic. Too much vitamin D causes calcium to be pulled from the intestines and bones and deposited in soft tissues all over the body, damaging the kidneys, heart and blood vessels. Dark skin screens out UV radiation and your body, which uses UV to produce Vitamin D, produces less of it - a real evolutionary advantage at the lower latitudes where we all began.
Insufficient Vitamin D would then result in a child developing rickets. A child with rickets would not likely reproduce either because it would die before it could or because its pelvis would be so deformed it could not pass a child through the birth canal. Its genes would be lost forever. So lighter skin, and more absorption of Vitamin D at higher latitudes would be an adaptive genetic advantage. Interestingly, in high latitudes where some people still retain dark skin, such as with the Inuit in the Arctic, the people obtain significant amounts of Vitamin D from eating fish and sea mammal blubber. This is all getting a bit scientific . . . LOL!
So what does this all mean? Are we all different races? Should we be labelling ourselves . . .? What we have instead of the meaningless terms Caucasian, Negro, Asian, etc, is a large multiplicity of ethnic lineages, all of whom descended from a only a single black race. So don't forget . . . next time you fill in the diversity part of your next application form, you should write in the word 'Black' next to the question about your race, regardless of your shade of pale.