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Mapping Human History, by Steve Olson (Houghton Mifflin)
It’s the history of all of us. . . and we’re more a like than most people know.
Mitochondrial Eve (our common female ancestor) lived fewer than 200,000 years ago and thus shows the recency of our common ancestry. “Some people might like to believe that genetic mixing of people from different groups is rare—and that their ancestors certainly didn’t mix with hoi polloi. But groups have many ways of mixing.”
By comparing the DNA sequences of people all over the world, geneticists have found 85% of the total amount of genetic difference in humans occurs within groups and only 15% between populations. As the author puts it, “In other words, most genetic variants occur in all human populations. Geneticists have to look hard to find variants concentrated in specific groups. This pattern is not most found in other animals. Most biologists feel that group genetic differences have to exceed 25%-30% for a single species to be divided into subspecies or races. By this measure, human races do not exist.”
That is a profound statement! “Most African-Americans have European ancestors; all European Americans have African ancestors. Race disguises rather than acknowledges our multifaceted histories.” Showing how insignificant these differences are the author states, “The genetic variants affecting skin color and facial features probably involve a few hundred of the billions of nucleotides in a person’s DNA. Yet societies have built elaborate systems of privilege and control around these miniscule genetic differences.”
Just think about it, just ten generations ago each of us had 1,024 great-great-great-great-great-great-great-great grandparents and most of us got our surname from just one of them. Twenty generations ago, we each had more than a million ancestors and at thirty generations we had more than a billion—more than were actually alive back in the time. This is the result of what the author terms “circles of inheritance”—whereby you have individuals contributing to your ancestry through more than one branch of your family tree. It has to do with cousins marrying each other and gets quite complicated.
The end result reminds me of two infamous songs, We Are The World and We Are Family. So, shouldn’t we be able to get along better?