OK, I don't want to take up too much space here and the response I first wrote was mostly just me identifying problems and then coming up with solutions to them a few lines later (i.e. I was mainly just rambling). I think it's just really hard for me to accept evolution in a direction that is in any way harmful to the species. I can't get over the fact that the peacocks are polluting their own genetic pool with genes for this ridiculous plumage that has negative fitness consequences for them. I've reduced my ramble with most of my problems solved and unsolved to microprint below. Ultimately it boils down to my belief that the negative consequences of the retention of these genes to an N-2 generation should overwhelm any marginal benefit the species gains from speed and accuracy in female choice. You can blow it up and read all about it if you've nothing better to do. It's my problem, though, so if it's TL and you D want to R then that's cool too. I'd probably do the same.
TLDR Warning!
So the female selects the male with the fanciest gaudiest plumage.
This plumage takes a big toll on the male peacock in terms of energy needed to grow it as well as to haul it around with him. It slows him down and helps him get eaten by predators. Natural selection should kill this little trait off in only a few generations yet it persists. The reason is that the females select for it, but this is what I don't understand. Why would females select for a maladaptation?
The classic logic that everyone is taught in high school is that the males who have the fanciest plumage prove their healthiness to the females by having been able to survive so long with such a ridiculous display, so the females are all "Oh he's a vigorous young cock isn't he? Look at how he survives despite the odds! I'll take him." Well that seems pretty logical and I never really gave it much thought until later.
So my current problem is like this. First of all, it bothers me that we're anthropomorphizing so much in this little example when evolution is a blind and mute unconscious non-conscious force of nature. I prefer to simplify things by looking at just the operative evo forces in isolation and weighing them against each other.
With that in mind let's start from the proto-peacock - a shapeless blob - in a pre-sexual-selection environment. Discounting the possibility that the development of the silly plumage gene (SP) is a fitness-linked trait at this point, there is no force that would prompt its emergence except random mutation. I understand the need for sex as a means of variation so mutations would be a natural and good thing here. Well eventually one of these proto-peacocks from among the spectrum of proto-peacocks with differing degrees of fitness would begin to develop the SP phenotype. Chances are first SP carrier would be of average fitness, but let's really force the issue and imagine it was the healthiest of that generation which began to display SP traits. So that peacock - the first real peacock - would pass on the most offspring who are carriers and they would be genetically the finest peacocks and the line would continue until today. Now we have the high school explanation stripped of its anthropomorphic nature. But there's a kink that develops even at this early stage. If we look at the fitness potential of the male proto-peacock in pre-sex-selection times, it turns out that the first SP carrier can't be the peacock with the highest possible fitness because the SP trait is a negative one in terms of fitness in a pre-sex-selection age. The best the first real peacock can hope for is placement at second best or so. I suppose this could still enable it to become the dominant line after sex-selection begins because the SP carriers are certainly easily recognizable so the females may not be so fussy as to reject the second best in hopes of holding out for the best. OK let's assume that's the case. So that explains the peacock's emergence from the proto-peacock, although it really breezes over the portion about the start of sex-selection - I guess the theory is that with female choice the females should be able to quickly and immediately identify the fittest males so they don't end up waking up next to a disguised runt the next morning. Still kinda bothers me though. The more the SP trait is developed, the further from the peak of fitness they drive themselves. I suppose they only need to stay around the top so although what they've got now seems ridiculous to me it's nowhere near what they could produce if there were no negative consequences. So I guess the forces to increase size and decrease balance out around where we have it today. OK so from the male's perspective I guess I can kind of see it, although it still seems like a strange coincidence that there was no better and still visible trait that they could have developed like a single mammoth feather or a blazon of iridescence or something.
So let's examine the pros and cons from all relevant perspectives:
Female: Pro- it indicates membership in the upper echelons of fitness and it is so striking that we females immediately recognize its worth. We don't care about the males because all we need is their genetic material to pas on to have vigorous offspring.
Males: Con- We are constantly getting eaten by other animals despite our fitness. We only do it because the females force us.
N-2 Generation: Net Con - Female progeny unaffected, Male progeny highly likely to be SP carriers and thus healthy in body but unhealthy in adornment.
I see a net negative here. Granted there is no indication of the magnitude of these forces, so the benefits to the female may outweigh the benefits of all others, but my gut tells me the strongest force should be determined by the offspring who get a net negative by the retention of this nasty gene.
Sasha!!(Read 25736 times)