Women are cheaters too. A look into female extra-pair copulations with other males

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Sometimes, females will sneak off and copulate with males who might have better genes, while their normal mate is a better father (in terms of effort, territory and resources). The theory is that the females do this as a way to potentially increase the quality of her offspring (if some happen to be fathered by the extra male), but retaining the highest quality father. These events are called extra-pair copulations. This has been well studied in bird species.

It has been shown to happen in animals, but what about in humans? There are women who do this, commonly known as cheating, and sometimes even while their normal partner is aware of the extraneous activity. The latter type of case might be super rare, but maybe it is not so rare as we think. Maybe instead of thinking of the extra lover as having better genes, we should think of it as the female being inexplicably attracted to another male but not willing to give up her usual mate. Without getting too deep into the issue of cheating, this post will talk more about the ecological implications for such behavior.

I should also mention that this is bigger picture stuff. In the case of birds, each female bird may not make the decision with an understanding of the potential consequences. But, in the bigger picture her actions may affect her overall fitness and the fitness of her offspring. Fitness is a concept that is often misconstrued in general media. Being more fit does not necessarily mean you are faster or smarter that others in your population. Fitness is literally how many genetic copies of yourself you put out there in the next generation (aka your kids). Traits like speed or smarts can help you survive better to produce more offspring, and that is where they play into fitness. “Survival of the fittest” should be “survival of the genes of the fittest,” but that isn’t quite as catchy.

You might think to yourself that humans don’t think about passing down their genes, but how many people choose to adopt children (who very much need homes) over having their own child who looks like them (if they are able to)? I’m guessing not very many people (and according to Facebook, many of my friends have already birthed mini-versions of themselves) and there is nothing wrong about that. Most evidence of altruism is based on genetic ties, or personal gains in some way, so it would make sense that it wouldn’t be common for someone to adopt a child totally unrelated to themselves. (But thankfully, some people do adopt! Go adoption!)

I don’t want to overemphasize genetics, but it is an important underlying concept. There are definitely cases where women cheat with no genetic benefit at all. In the movie The Other Man (which my friend Chad told me about), the woman had no reason to cheat, and no intention to have more children with her lover. But she does it anyway. There may not be a reason, and perhaps there doesn’t need to be. She chose to do it and she was aware of what she was doing.

But going back to scientific ideas, some questions for further investigation might be:

  • how common is this in human populations?
  • and what are the benefits to fitness strategy (if any)?
  • is it a valid strategy? (i.e. do the offspring end up getting better genes?)

Where do you think this fits into our biology?


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