Who would have thought, but flies also have penises? Good for them (someone answered me to this statement)! But their penises have all kinds of hooks, tepi etc. Good for them!
Beyond jokes, Darwin likened the role of these seemingly strange ornaments to the famous peacock's tail. They would be involved in sexual selection, females would choose the most decorated males. This would be called pre-insemination selection, because it seems like insects (but not only) there is also post-insemination selection. That is, the male who had sex with a female cannot sit still after that. Because his fight for reproduction continues, being carried away by his sperm, which competes with that of other males. Females mate with several males in a short period of time (and better for them!). And all these decorations would have the role of removing the sperm of other males that have mated before. This idea, difficult to test directly, it is suggested by the fact that the mating ritual begins in some insects only after copulation has begun.
Only laser technology has recently allowed this hypothesis to be tested. Michael Polak of the University of Cincinnati, Ohio and entomologist Arash Rashed from the University of California, Berkeley, they played a little with doctor Ciomu, and they cut some thorns from the penis of some flies. Surprise, these males could no longer mate, them sliding off the flies during copulation. These spines therefore had the role of fixation during sexual intercourse. If they still managed to complete their mission, males without spines were as fertile as those with spines.
But now comes the interpretation of the study: spines and their role confirm Darwin's hypothesis, they being the result of pre-insemination sexual selection, not post-insemination. A kind of peacock tail, which is known to have no functional purpose. Of course, there were also some who said that it is not excluded that females could invest less in the sperm that comes from a penis without thorns (fewer nutrients), this if they have the opportunity, to understand.
How would we interpret this in humans? It is quite difficult to make an analogy because people have developed brains, I think complicated, au behavioral control. Let's say that women prefer men with erections, not with a flaccid penis, who have more offspring, that's why erection is quite common... It's pre sexual selection- or post-insemination? We could say that it is simple operation, possibly natural selection, even if it appears in the sexual sphere. The same with midges. But…
http://sciencenow.sciencemag.org/cgi/content/full/2010/106/3?etoc
