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On Sex

2 Mar

On a winter evening some years ago, my wife Cheryl met me at the door when I came home from work. “Don’t blow your stack about it. There wasn’t much damage,” she said.

With three teen-age boys, I’d heard this before and knew that “not much damage” is an ambiguous and misleading term when the speaker is not the one who writes the checks.

“Trevor was driving your car home from high school,” Cheryl explained, “and the car went into a skid on that slippery corner coming down the hill. The car slid into a snowbank—no one was hurt and no damage was done.”

An outcome that unremarkable didn’t sound normal for my family, but I could take that. I’m resilient. I didn’t even bother to look at the car, just picked up the newspaper and made myself comfortable in my recliner. Tyler, our youngest son, came into the room as I was reading the comics.

“Hey, dad! Did you hear about Trevor’s accident?” he asked. “I was riding home from school with him when he spun out. Man, if it hadn’t been for that fire hydrant he hit, we’d still be plowing down-hill across lawns.”

I put on a coat and checked my car—bumper dented, fender crinkled, headlight broken—and prayed there was no damage to the fire hydrant. This outcome was normal for my family.

I’d been reading scientific papers that considered the cost-benefit analysis of sexual reproduction in evolutionary terms. After all, why should complex animals have developed something as expensive in time and energy as sexual reproduction when so many life forms just split into two?

It had been posited that sexual reproduction provides greater genetic diversity and improved resistance to parasites and diseases, an opportunity for more rapid evolution, better protection against damaging mutations, or all of the above.(1-4) The leading benefits seem to be staying ahead of parasites and pathogens and cleaning up harmful mutations in the genome.

The data looked compelling, but nowhere, and I mean absolutely nowhere, in the papers was there any mention of the cost of auto body repairs. The omission was inexplicable, for although the scientists working in this field probably didn’t know my kids, at least some of them must have known other teenage boys.

1. Zimmer, C. On the origin of sexual reproduction. Science, 2009;324(5932):1254-1256
2. Jokela J, Dybdahl MF, Lively CM. The maintenance of sex, clonal dynamics, and host-parasite coevolution in a mixed population of sexual and asexual snails. Am Naturalist 2009;174 Suppl 1:S43-53.
3. Morran LT, OG Shmidt, IA Gidarden, et. al. Running with the Red Queen: Host parasite coevolution selects for biparental sex. Science, 2011;333:216-218.
4. Hussin JG, Alan Hodgkinson A, Idaghdour Y, et al. Recombination affects accumulation of damaging and disease-associated mutations in human populations. Nature Genetics, 2015; DOI: 10.1038/ng.3216