New evidence forces us to consider the role of genes in all behavior
Just over a quarter century ago, I wrote my first book, The Tangled Wing: Biological Constraints on the Human Spirit. In it I addressed the objections that many liberal scientists and others of that day had against behavioral genetics, some of which I shared.
But I also pointed out to them that the pace of accumulating evidence was such that it would not be possible for much longer to deny any meaningful role for the genes in human behavior. I thought they should ask themselves: How much do I really believe in democracy and equality for all? Only as far as I can deny that people differ for partly genetic reasons? Or really and truly, regardless of those differences?
I was reminded of this when I opened the mail this week and found the latest Science, America's leading scientific journal, the cover proclaiming a special issue on "The Genetics of Behavior." It covers a range of research findings from the behavior of the honeybees on the cover to humans with our complex brains. It's normal science now, and the aura of political danger has almost completely lifted from it.
The dangers were real. In the mid-19th century "scientific" anthropology was used to denigrate Africans and justify enslaving them. In the late 19th century Darwinism was twisted to justify the worst ravages of class, caste, and colony. In the 20th century "eugenics" was used to justify forced sterilization and then, after a long slide down a slippery slope of inhumanity, the mass murder of millions of Jews, Gypsies, homosexuals, "mental defectives," and others.
But in the 21st century we have a new context and a new problem. The context is one of greater acceptance than ever that race explains almost nothing that is intrinsic and important. The problem? Research on genes and genomes, including behavioral research, is rushing along at such a pace that we have to face it head-on and not deflect or deny it. Ignored, it will fester and once again breed horrors.
Take this new issue of Science. Some of it is just ho-hum stuff about work ethics in honeybees and mate choice in fruit flies. Actually it's not ho-hum, it's gee-whiz, but only to those of us who care about such arcane things. The average normal person thinks, "Okay, so a fly can't pick a girlfriend without consulting his genes. What does that have to do with me?"
It gets a tad more uncomfortable with mammals like mice and voles. Little, yes, dumb, definitely, but in many ways they work a lot like we do.
So when it turns out that mother love in these cute critters depends on the genes for oxytocin signaling in the brain, while male commitment to a long-term relationship depends on the vasopressin, another hormone that is also a neurotransmitter–well, that's when I get young women in my classes coming up to me afterwards asking how they can change their boyfriend's genes.
Science fiction? Maybe not. In a Swedish twin study, a vasopressin receptor gene variant was associated with poor commitment in relationships—in men only. And oxytocin has been found in numerous human studies to be related to trust
But when it turns out that aggressiveness—as in some people's warlike nature—is linked to a gene for the brain enzyme monoamine oxidase, and on top of that when you find that the New Zealand Maori, traditionally warriors, have more of the aggressive variant than Caucasians do, you might get the chills as I do.
Alright, the difference is only between 60 percent of Maori (like other Asians) having the variant versus 40 percent of Caucasians, and we Caucasians are a very warlike tribe ourselves, so you can bet there are other things involved, including other genes. But still, we're into politics here, and genes and politics always make a volatile mix.
That's not all. Political involvement is itself quite heritable. You are more likely to vote or otherwise participate in politics if your biological parents did. Family environment matters, but not as much. Not only that, but brain imaging studies show that those who participate in politics react to political issues with increased activity in the same cortical areas—the medial prefrontal and medial parietal–that are activated in social relationships. Nonpolitical folks deactivate the same areas.
That means Barack Obama and John McCain may have been born with the same genes for becoming intensely political animals.
But what about the kind of politics we advocate? Do genes influence whether we are conservative or liberal, Democrat or Republican? I'll take that up in another posting, but meanwhile one thing is clear: the relationship between genes and complex human behavior cannot be denied.
In 1982 denial was still a workable strategy, and many liberals took the position that the evidence for genetic effects on behavior wasn't there. But I issued a warning that is far more true today: "The sands of scientific time are shifting beneath that position, and those who tend it had best look to a foothold."