Science Sundays: sexual selection

By: Meradeth Houston on 9:48 AM

Welcome back to Science Sundays! I thought we'd delve a little into the interesting and complex world that is sexual selection (it's a crazy world, and one that is always sure to get my student's attention!). So how can this fit into your writing? Well, it influences the natural world quite a bit, and there has been some suggestion that humans, especially when it comes to ornamentation, also have sexual selection at play. Maybe with some of the underlying concepts you can give me some ideas!

Okay, here's what sexual selection actually is: it's a form of natural selection where the reproductive success of one sex is more variable than the other, and therefore there are selective forces that create adaptations that allow for more matings (and not necessarily just survival). In plain natural selection, adaptations are all about reproductive success--passing along genes and surviving to be able to do so. Same goes for sexual selection, but some of the adaptations that arise don't always make an individual the best suited for their environment.

Examples: take the giant antlers on the deer that are roaming around in my backyard (I think hunting season's begun and they're hiding here), those antlers take a HUGE amount of energy to produce, maintain, and don't make it any easier for a deer to run fast through the woods. They'd be better off without them. BUT, they do attract the lady deer, and allow for fighting off other males who want to mate with it's ladies. The same kind of thing goes for the huge size of male walrus--they are so big they can hardly move on the ground, but they can certainly fight off other males from sneaking in and mating with their women. Fun right?

Now there are two general areas where sexual selection comes into play, the first is intra-sexual selection. This is where males (due to the fact that their reproductive success is more variable than females) fight with one another to get mates. Both of the above examples are intra-sexual (between males) selection at work. The male with the biggest antlers/size and best fighting ability will get the most mates (usually--there are exceptions of sneaky males :).

The other type is inter-sexual selection. This is where the reproductive success of one sex is determined by the pickiness of the other sex. This one's my favorite, because this is where you get some of the most crazy strange traits showing up. Personal favorite? The giant NOSES on the proboscus monkey--who think's that's sexy?? Well, apparently the female monkeys. Biggest nose = more mates. Fun times! This kind of selection is really common in birds especially, which results in all kinds of awesome feather colors (think peacocks), strange mating dances, calls, etc. etc.

What about humans? Well, not all mates are created equal. (I think that's pretty obvious, yeah?) So members of both sexes will try to attract the highest "quality" mate, depending on what they think that is. So we see all kinds of random use of ornamentation--flashy cars, expressions of wealth, showing of "assets." Can you think of anything else? :)

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So, how might sexual selection play into a story? Can anyone think of anything?