The Bigger the Testicles, The Smaller the Brain
Now there’s a title that ought to catch people’s interest. Researchers have discovered an inverse relation between brain and testicle size among bat species.
In species where females mate promiscuously, male bats have proportionally larger testes and smaller brains. In species where females are monogamous, the reverse trend holds true.
The evolutionary hypothesis on why this exists is a good one. Since both brains and testes require lots of energy to maintain, there may only be energy for one or the other. In species where females are mating with multiple males, natural selection is strongly going to favor the male that can produce the most sperm. When that’s not an issue though, it makes sense that brain size and function is more useful than producing lots of extra sperm that aren’t needed.
I think other scientists should be quick to pick up on this work. I hypothesize that for any guy who’ll brag about his own, um, endowment, you’ll find the same inverse relationship holds true.
How are the females choosing mates in the monogamous species? Does it have anything to do with brain size/function?
I have no idea Kelley. I came across the news article, not the scientific paper, so my knowledge is limited.
I’ve often been fascinated how sexual selection can push things in the opposite direction from natural selection. My first post on evolution talks a little of this and gives the example of John Endler’s guppies from South America.
Back to the bats, I have no idea how females are choosing their mates. The article didn’t say, and if they don’t know, that would be a very interesting question. ln my post, I simply guessed that if they lack a strong selection pressure for larger testes, then brain size would be allowed to increase and perhaps even favored by natural selection.
To put it another way, with my reading of the article, I think it’s a good conclusion to say that sexual selection caused testes to get larger and brains smaller. The article didn’t say why the reverse happened, and thus I took a guess.
It has been stated that the Creator made men with brains and genitalia, but with only enough blood for one or the other. Ergo, if one is perfused, the other is, to be gentle, hypoxic.
Perhaps a similar phenomenum is at work on an evolutionary scale….