Viagra & Evolution

As noted by others this is not a problem at all for the evolutionary model.On a purely speculative note there is another possibility:If the environment changes too quickly a species may no longer be well suited to it. If it doesn't evolve fast enough then extinction is the result. This is what will happen to all species, us included.Perhaps we are changing the environment too quickly with a chemical stew and we are seeing the very earliest signs of this.

and if most humans reproduce then the larger population with have very great genetic diversity. A change in gene frequencies of populations over time is what evolution is.It will continue even if we do reduce selective pressures. By the way, I am in agreement with you that we have not reduced all pressures and I think we have increased some. For one, our denser populations are probably putting pressure on to help select "tamer" humans.

If this sort of "crowding" mechanism works in humans I think it would have to be because we've carried it from waaaaaay back in our evolutionary past.I doubt very much that any of our genus (or close relatives) have had much crowding of population in the last 10 million years at least. That is until the last few 1,000.Rats have been subject to this for a very long time I'm sure.