Non-human Behaviors That Get Genes Copied

by John Carroll




As I point out in Biology and Politics, each critter's behavior is fine-tuned so that in the appropriate environment, it produces new copies of its genes for the next generation. The biology books are full of such behaviors, but I thought just this once I'd give some examples I happened to notice in the wild that I hadn't read about. Okay, I've got an excuse. I promised a new essay would go on the web today, and the one I was working on, showing the struggle between different sub-tribes of Americans for resources is taking a lot longer than expected, and I ran out of time. So no humans this week, just "critters," gathering resources and/or turning them into viable new animals carrying their genes -- or somebody's genes. So here are three vignettes.



1. RIDING THE BEETLE

Back in 1982 I spent a couple of months living alone in the woods. Never mind why. I can say good things about it and bad things -- the baddest thing being the lack of people to talk with, and the goodest being watching the critters struggle for existence. It was late summer and the area along the dirt road, if you could call it a road, was festooned in goldenrod and thistles, and on the goldenrod flowers, I discovered a strange little beetle. The female appeared to spend her days grazing on the flowers. I assume that was the female, because on her back was perched another beetle, a bit smaller than she was. He never ate and never seemed to leave. He'd ride her for days, near as I could tell. My guess, of course, is that the rider was the male, having sex and protecting his sperm's chances of fertilizing the female's eggs by staying in place. Whether he ever left her, or just starved and fell off eventually, I don't know. It struck me as not such a bad life, though. Spend most of your adult life having sex! Of course it would be nice to have a longer life, and at least for the female to notice she was having sex, or to stop now and then for a sandwich, or just to relax and take a shower, but it seemed to suit the little male beetle, and the female seemed to ignore him completely as she grazed on the goldenrod, gathering the resources that would produce viable copies of her genes and his.



2. PREDATION AND CANNIBALISM


It was at that same campsite, maybe ten miles down mostly dirt roads from the town of Locust Grove, Virginia, that one night I got bored and decided to see how the creatures of the night lived. Hadn't gone far down the path I'd made when I spotted a cricket eating a daddy longlegs. And standing off to the side, maybe half a foot away, was another daddy longlegs. The cricket ate as much as it wanted, then hopped off into the night. That's when the daddy longlegs that had been observing all this, approached the body of its comrade and seemed to be eating the remains. I'm not sure how daddy longlegs eat, actually, but there seemed to be no other motive for mauling the body. A little midnight cannibalism. I continued down the path another ten yards or so, and there I spotted two daddy longlegs wrestling with one another, one of them brown, the other a different color, probably black, but I don't remember. What I do remember is the sight of sixteen quivering legs, and the sudden moment when eight of those legs quit moving. I'm told those animals have a powerful venom, but fortunately in quantities too tiny to harm a human. The winner ate the loser, and I moved on, thinking of the awful competitions going on around me, reminded by the occasional mosquito bite that I was prey, too, and feeling grateful that I was the biggest animal in that forest.




3. MORALITY AMONG THE SPARROWS


I was just sitting in the back yard, back when I still had a back yard to sit in, writing what was slowly becoming a book called Biology and Politics, and amusing myself when I got bored by tossing bits of bread to sparrows. It was the time of year when the young sparrows were out of the nest and flying, but they weren't flying all that well yet and they hadn't figured out how to compete with the rest of the world for food, so they begged food from adults. A little one would approach an adult male sparrow who'd grabbed a piece of bread I'd tossed, and would crouch low, partly spread its wings, look at the adult bird, utter a pathetic little "peep," and open its mouth wide. The male would inevitably respond by stuffing his bread into the little beggar's beak.

At first I thought maybe the adult was the little bird's father, but then I saw the same youngster beg successfully from two different males. Then I guessed that adult sparrows are just programmed to feed any little sparrow that asks. That satisfied me for a while. Then it occurred to me that the youngsters never begged from females, only from males. A little later I found out why. A young bird begged a big piece of bread from an adult male. The male flew off and grabbed another piece of bread, and the little one struggled to swallow the piece of bread the male had given it. At that point an adult female landed next to the little bird, yanked the bread out of its beak, and flew off to eat it herself. I watched while she ate, and she certainly didn't look like she felt guilty. And the little bird didn't seem mad, but just hopped off in search of another male with bread to give. Nor did indignant neighbors mob her for stealing from a youngster. I guess that's just the way things are in sparrow life. Their morality is a bit different from ours. A reminder that critters evolve not to be moral or immoral, but to pass on copies of their own genes, whatever behavior it may take to do that. I can only guess at the selective pressures that led to male provisioning and female theft in the case of adult sparrows dealing with fledglings and why humans in every culture find adults who steal food from children contemptible.

Copyright © 2003 by John Carroll

These are a few of my own observations. I'd be glad to hear similar ones about non-humans or humans from anyone who has a story to tell. Just fill in the text box below, and add your email address and permission to use your story on this site. If I use it, you'll get full credit.



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