Thursday, September 20, 2012

Race Is Artificial


As you can tell by the articles below, the concept of race and nations is really rather artificial:
When applied to the question of who is descended from whom, the results can surprise even the professionals. That's because geneticists normally study biological information - DNA - that people inherit from just one of their parents. Just like a surname, or the male lines of descent quoted in the Bible, these generate lineages that shrink or expand rather slowly. That's why we expect the proportion of Smiths in the phone-book to fluctuate only a little from decade to decade.

The surprise comes if we look at inheritance from both parents. Here, the numbers change drastically as the generations go by. For instance, we have two parents, four grandparents, eight great-grandparents, and so on. Each generation back, we multiply the number by two. This leads to what is called an exponential increase: 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 and so on. It's not long before we hit huge numbers. Take the specific case of Jesus and King David.

The number of generations between them is at least 35. Luke lists 42 generations down the male line, and Matthew gives an incomplete list of 27. Jesus Christ would have had more than 34 billion potential ancestors These numbers agree reasonably well with an average time between generations of 25 or 30 years - an estimate taken from documented historical records from Iceland and Canada.

So back in the time of David, Jesus would have had at least 2 x 2 x 2 x 2 (35 times); in other words 2^35 - or more than 34 billion potential ancestors. That's far more than the total population of the world, of course. This is a good illustration of what's been called the "genealogical paradox".

You are unlikely to be the product of inbreeding between recent ancestors. So initially, your increase in ancestors will indeed be almost exponential. But as your family tree increases to thousands upon thousands, you will inevitably find many obscure branches that have interbred. That's when the numbers start tailing off.

Even so, by that time, you will have collected a large number of people in your ancestry. So it's not surprising that any two people in any one country probably won't need to go back many generations before finding a common ancestor. More specifically, imagine the simplest case of a population of a constant size - say a million (the approximate size of the Holy Land at the time of Jesus). If people in this population meet and breed at random, it turns out that you only need to go back an average of 20 generations before you find an individual who is a common ancestor of everyone in the population.
Family trees: Tracing the world's ancestor (BBC)

In the future will we all look like Brazilians? Fine by me, plus it gives me an excuse to post a picture of a Brazilian hottie at the top of this post:
It really happened: Six generations of inbreeding spanning the years 1800 to 1960 caused an isolated population of humans living in the hills of Kentucky to become blue-skinned.

The startlingly blue people, all descendants of a French immigrant named Martin Fugate and still living near his original settlement on the banks of Troublesome Creek when hematologists studied them in the 1960s, turned out to have a rare blood condition called methemoglobinemia. A recessive gene was pairing with itself to change the molecular composition of their blood, making it brown as opposed to red, which tinted their skin blue.

The hematologists' attempt to trace the history of the mutant gene revealed a gnarly Fugate family tree, contorted by many an intermarriage between first cousins, aunts and nephews, and the like over the generations. Dennis Stacy, whose great-great-grandfather on both his mother's and father's sides was the same person — Henley Fugate — offered a simple explanation for the rampant interbreeding: In the old days in eastern Kentucky, Stacy said, "There was no roads."

It sounds sordid at worst and lazy at best, but in fact, the Fugates' tale is a miniature version of the story of human coupling since time immemorial. Local populations interbreed, causing a sharing of genes, a resulting in-group physical resemblance and, eventually, identification as a distinct race or ethnic group.

According to Stephen Stearns, a Yale professor of ecology and evolutionary biology, before the invention of the bicycle, the average distance between the birthplaces of spouses in England was 1 mile (1.6 kilometers). During the latter half of the 19th century, bikes upped the distance men went courting to 30 miles (48 km), on average. Scholars have identified similar patterns in other European countries. Widespread use of bicycles stimulated the grading and paving of roads, lending credence to the Fugate clan's excuse and making way for the introduction of automobiles. Love's horizons have kept expanding ever since.

"The distance between the birthplaces of parents has continued to increase since the invention of the bicycle, making it now easy, if not standard, for parents to have been born on different continents," Stearns told Life's Little Mysteries, a sister site to LiveScience. Meanwhile, many other physical traits will simply blend together.
"Most of the traits that we think of as distinguishing different groups (hair color, skin color, hair curliness, facial features, eye shape) are controlled by multiple genes, so they don't follow a simple dominant/recessive pattern," McDonald explained. "In those cases, blending will make people look more similar over time." It's not straightforward to predict how blending of genes affects physical appearances, but McDonald said the tendency is for such traits to average out.
The average American skin and hair color will probably darken slightly, and there will be fewer people with very dark or very pale skin and hair. A population forged from the long-term mixing of Africans, Native Americans and Europeans serves as an archetype for the future of humanity, Stearns said: A few centuries from now, we're all going to look like Brazilians.
Will Humans Eventually All Look Like Brazilians? (Live Science)

Of course Peak Oil might put a stop to that. At least we still have boats. And did you know all blue-eyed people are descended from a single individual? For the record, my eyes are hazel.

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