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This is the journey of your (and my) family. Scientists like Spencer Wells have been using our DNA to create a family tree of the world and they've found some rather surprising results. First of all, we're all related. In a sense, we're all cousins. Secondly, about 50,000 years ago, all humans were still in Africa and there were perhaps as few as 10,000 of us.
Our species was on the brink of destruction, but somehow, in the blink of a geological eye, we not only survived but conquered virtually every corner of the planet. Think of it like this: We share a common ancestor with apes and apes first appeared on the scene about 23 million years ago (or perhaps 25 million years ago). If we compress that 23 million years down to just one year, the first apes appear on January 1st. The first hominids (man-like apes who walk upright, think Australopithecus or Lucy) appear some time in late October. The first anatomically modern humans (if you dressed one in a business suit, he would be mostly indistinguishable from humans today) hit the scene about December 28. On the 31st of December, we leave Africa and by January 1st of the next year, we've managed to populate and inhabit virtually all of the planet.
So how do we know any of this? Well, some of this knowledge comes from the fossil record. But recently with the advent of genetics and computers to analyze the human genome, scientists have discovered how to use our DNA as a sort of time machine.
Here's how it works: All males have a Y-chromosome (it's what makes you male!) and they have just one, which is an exact copy of their father's Y-chromosome. Since your mother could only have given you an X, if you have a Y, it had to have come from your father. In this way, we know that your Y-chromosome (if you have one) is the same as your father's and his father before him and his father before him and so forth and so on all the way back to a man living in Africa sometime around 50,000 years ago. If that's hard to imagine, try this: Imagine you are holding your father's right hand. Now imagine that while holding your left hand, your father is holding his father's right hand. Now just imagine a chain all the way back to an African 50,000 years ago (it's only about 1,000 generations or so).
"How does that help anything," you might be asking. "If you just get a perfect copy, how are you supposed to tell anything about the past?" Well, if we did get "perfect" copies, we wouldn't be able to tell anything about the past. But fortunately for us, every now and then, when the Y-chromosome is making a copy of itself, it makes a mistake. These mistakes are almost all entirely harmless. But once they're there, they get dutifully copied each time and passed to every offspring that inherits that Y-chromosome and each of their offspring and so forth and so on. It is through these "Y-makers" that scientists are able to trace the progress of humans around the globe.
Because scientists like Wells have tested the Y-chromosomes of isolated tribes in Africa, they know that we are all descended from Africans. In a sense, we're all still African, we just haven't been home in about 50,000 years. They have Y-markers that everyone else on the planet has, and none of the other ones that we have. In this way, we know that people living in parts of the world other than Africa must have left before the new mutations in the tribe appeared, or some of the people in the rest of the world would have these mutations too.
So what's our family tree like? Well, the first or our ancestors to leave Africa went pretty much straight for Australia, through the Middle East and then along the coast of India, leaving their Y-markers in isolated regions of India and then in isolated parts of Australia. Australian Aborigines are more related to the isolated African tribes (and in turn our African ancestors) than even some Africans.
After our first migration, we made another. This time we went for Central Asia. From there some of us continued to parts of China and some of us stayed. After a while, the Central Asians went on to populate most of the rest of the world. Europeans, Native Americans (both North and South), Asians and Russians are all descended from Central Asians about 40,000 years ago.
It is truly an amazing story and if you're interested in learning more, you can watch the documentary starring Wells on YouTube: The Journey of Man. It covers all of this and a lot more.
I am interested, however, in what it means for human relations (among other things). Because we're descended from only 10,000 (at the least) individuals, we're all extremely genetically similar. We share about 99.9% of our genes with each other. In fact, we're barely different enough from chimps to have our own genus, we still share about 99.4% percent of our genes with them. We're all really one big African family. In fact, it's pretty much impossible to find someone on the planet who you're not related to.
Concepts of race are merely social constructs. While they are useful to anthropologists, they have no use for the rest of us. We need to stop thinking of each other as different races. We're so similar that such a concept is ridiculous.
While there are obvious differences between us, they are almost entirely arbitrary. Hair color, skin color, facial structure and other such differences are the tiniest fraction of what makes us human. Furthermore, it's not as if any "race" has a feature that any other race couldn't have, they just have it in a higher frequency. It's not as if Europeans are incapable of having dark skin, it's just that most of them don't. While the differences are due to evolution (though not all to natural selection, I suspect a great deal of variation is due to sexual selection given that we are so picky), 50,000 years of evolution is not really enough time to create anything but the most arbitrary of differences.
Try to remember this article next time you see a story on the news about those suffering in Darfur, or the plight of other peoples in far away lands. Don't think, "Who cares about those people, they're all the way on the other side of the world." You should be thinking, "That's terrible! Those people are my cousins! Just 50,000 years ago our fore fathers were in Africa living together! Something should be done to help my family."
