INCEST IS BAD, PART MMCVIII
Nobody likes an inbreeder. While it does happen in a variety of animals, obviously including humans, Nature doesn’t care for it. She has a way to mark your face if you’re a product of incest.
Nature is a little more direct than Nathaniel Hawthorn. He made the mother of the bastard wear the scarlet letter. Nature marks the offspring itself.
This is complicated, but bear with me: We know inbreeding is bad biology, right?
There’s the recessive gene problem, for starters. Imagine a brother mouse and sister mouse who both carry the gene for cross-eyedness. If they each had kids with unrelated mice the gene would receed into the background and their children would be normal. But if they breed together, the kids have a good chance (one in four, right?) of getting both copies of the cross-eyed gene.
And then there’s the sniffy business: Lots of animals, and according to recent research I’ve blogged about here, humans, can sniff out each other’s immunity profile subconsciously. We all pick mates whose immune system compliments our own, so that our offspring have broad immunity.
So now these gals have determined two things: Human males find a females face more attractive if her parents had very different immunity profiles. Somehow, this is reflected in her face, and males can detect it. Trippy. (The authors investigated males on females only; presumably females are as literate in facial cues.)
Secondly, they find that yes indeedy humans of both sexes whose parents gave them really diverse immune profiles are… drumroll… healthier. It works! Even we dull-witted humans can call on biology to guide us toward more bullet proof mating choices.
The definition of “healthier” here is interesting. It was very narrow: Just colds and routine stuff that the subjects contracted over the course of 4 months. So this doesn’t capture the bigger, badder stuff like cancer, blood pressure, cholesterol, asthma, hepatitis and other things that have a genetic component. They were only measuring how well the humans’ immune system responded to infectious junk.
Which makes me feel better about the “effect size” of this study. The whole immune profile thing could only explain 3% of the difference between individual healthiness! That’s tiny! But so was the definition of health.
Bottom line: Once again, science proves we shouldn’t have offspring with people we’re related to.
