Looking back over all my posts, about half of them have dealt with race. Nearly all of those are about what might be called "social race"--that is, race as a social concept. The term "race" used this way is a pseudobiological way of categorizing people; and categories of social race vary from one culture to another.
The human species has no races in the biological sense--all that exists is gradual variation in what people look like, with more distant populations appearing more different from one another than closer ones. "Biological race," in contrast to the social concept, is not one that applies to modern humans--even the question as to whether Neanderthals were a different race (i.e., subspecies) or a different species from our ancestors has not yet been definitively resolved. For this reason, only a few of my posts (1, 2, 3, 4) have dealt with biological issues related to race.
Here is one more reason that the human species has no races--this time using logic, the powers of two, and the facts about human population growth.
Every person has two biological parents, four biological grandparents, eight biological great-grandparents, and so on. In 10 generations that makes 1024 ancestors, and thereafter, using computer jargon, we're dealing in thousands, or kilo-ancestors. 20 generations mean 1,048,576, and thereafter millions or mega-ancestors. 30 generations mean 1,073,741,824 and billions or giga-ancestors. 40 generations mean 1,099,511,627,776 and trillions or tera-ancestors. (People who are curious about the implications of mathematical studies of genealogy might enjoy an article by Steve Olson.)
Before modern medicine and public health, people didn't live very long and reproduced when they were young. To be conservative, however, let's count 25 years per generation. 40 x 25 = 1,000, so that means that a thousand years ago, every human alive today has over a trillion ancestors. However, modern humans have been around for about 200,000 years, so it is easy to see that--adding another three zeros every ten generations, or 250 years--this accounting gives us more human ancestors than there are atoms in the universe.
There is another problem, however--the facts go in the opposite direction from the math. While the calculation of ancestors gives us numbers that explode in magnitude the further back in time we go, the actual history of the human species has been just the opposite. That is, we are actually undergoing exponential growth in the size of the human population, so that the further back in time you go, the smaller the number of humans. (See the first figure showing the world's population more than doubling during the second half of the 20th century.)
How can we reconcile this contradiction?
There is one clear answer. They are all the same people!
That is, your biological great-great-great-great-etc. grandparents and my great-great-great-great-etc. grandparents, and for that matter the great-great-great-great-etc. grandparents of everyone on the planet are the same people. Whatever the superficial differences in what we look like, in biological terms we are all closely related--too closely related for the human species to have races.
Population growth [1750-2000]
Exponential growth--the green curve shows how continual doubling rapidly surpasses linear and cubic growth.
Comparison between f(x)=50x, f(x)=x^3, f(x)=2^x
Check out my most recent book, The Myth of Race, which debunks common misconceptions, as well as my other books at http://amazon.com/Jefferson-M.-Fish/e/B001H6NFUI
Visit my website: www.jeffersonfish.com