Did DNA cause humans to migrate around the world?
I recently read that scientists have found a correlation between certain genes and behavioral traits like risk-taking. Are these genes more common among migrants — for instance, the descendants of U.S. colonists, as compared to the population of the UK?
No doubt it’ll thrill American exceptionalists right down to their red, white, and blue blood cells to learn that yes, the so-called “risk-taking gene” you reference is indeed more prevalent in the population of North America than on some other continents. But is this scientific proof that the U.S. truly is a nation of rugged individualists, that our DNA itself spurred us across the ocean to liberty? Hmm. Let’s pump the brakes here a bit, patriots, and look a little closer at the gene they call DRD4.
What sounds like the name of a toy droid at a dollar store is actually shorthand for Dopamine Receptor D4. Like many genes, DRD4 comes in several alternative forms, or alleles. About 65 percent of the population has the version where a certain nucleotide sequence repeats four times, and you don’t read much about these normies in the popular-science press. Everyone's way too busy talking instead about the less-common DRD4 variant, carried by about 20 percent of humans, that repeats seven times — which, assorted studies suggest, may predispose its bearers to seek out novelty and risk.
Though experts in behavioral genetics fruitlessly caution us not to treat our DNA profile as though it's some science-approved version of astrology, just about any non-playing-it-safe behavior you can display — substance use, gambling, general impulsiveness — has been linked to the DRD4-7R allele in a scientific study, with varying degrees of confidence, and then shouted about in the press, with varying degrees of accuracy. Thus we see a slew of stories in which DRD4-7R is billed variously as the “wanderlust gene” that drives you to splurge on exotic vacations, or the “slut gene” that makes you less likely to go home alone at closing time.
However it may affect people's conduct, the 7R allele isn’t scattered evenly worldwide. Back in 1999 researchers at UC-Irvine published the first study to find an association between higher incidence of the long DRD4 allele and long-distance prehistoric migration. A 2011 paper crunched the numbers finer and came up with similar results — showing, essentially, that the greater distance a population had migrated from Africa, the site of human evolution, the more common the 7R allele would be within it. (I say “essentially” because the 7R percentage in Asia is quite low — they're still puzzling over that one.) But that doesn't mean we know why or how 7Rs thrived in some areas more than in others.
And we'll be pretty much left guessing about that, unless somebody uncovers a long-buried stash of prehistoric diaries and psych evaluations. It’s not too tough to imagine how an inclination toward thrill-seeking, or other apparent 7R-associated traits (many of which we consider symptoms of ADHD) could play a role in a large-scale migration scenario, where natural selection might well favor the antsy adrenaline junkies and thin out the placid 4Rs who'd followed them into the unknown. Any such benefits may be context-dependent: among the Ariaal tribe in present-day Kenya, 7Rs who live as nomadic herders are on average better nourished than non-7R nomads, but 7Rs who've settled down don’t eat as well as the other villagers.
So though there's likely some relationship between migration and 7R, we can't jump from there to saying that 7Rs’ innate adventurousness drove them to travel further than their fellows. Which means we should be careful about assuming that a 7R gene is what keeps people wandering today. Of course, you don't need to be a geneticist to recognize an online screed headed “Why Middle Eastern Migrants in Europe Will Tend to Be Rapists and Criminals” for exactly what it is. (Yes, that’s really the title of a 7R post by some right-wing evolutionary-psychology blogger; you’d hope even the most credulous ev-psych fan would know enough to steer clear of creeps like this.) Current events should remind us that people choose to migrate for all sorts of reasons, and choose not to migrate for just as many. If we're just talking genetic predisposition, someone prone to taking risks might well decide to stay behind in Syria and fight, for instance.
The impact of genetics on behavior is too complex to be boiled down to a single “migration gene”-type mechanism, but with every new scientific discovery we go through the same rigamarole: scientists publish papers suggesting correlations; journalists and other lay writers read no further than the abstract and sensationalize what they believe to be the findings; scientists rush back in waving their arms saying, no, you can't quite say that. Lather, rinse, repeat.
In other words: if you're a high school smart-ass figuring you’ll pull your history teacher’s chain by answering “Why did the Pilgrims leave England?” with a snappy “Because DNA,” know that your risky behavior is likely to result in a low exam score. What if, despite that knowledge, you can't help yourself? Feel free to blame your genes. Everyone else does.