I would like to mention, as a reminder, that in any case evolution does not 'create' things, it merely weeds out things that are detrimental to survival and reinforces things that are advantageous. Thus, laughter could be something that does no harm but also has no particular advantage--but happened to be present in the group(s) that survived for other reasons.
Well, natural selection doesn't create things, but natural selection in combination with mutation certainly does.
And that's a very large part of what evolution is: mutation + selection.
Not everything has to have an evolutionary advantage to be present.
Definitely true. Not only, as you point out, does genetic drift cause traits that have no advantage to become fixed in populations, but if we look at particular traits we often categorize them wrong: not realising for instance, that it wasn't A that was selected for, but B, and A just happens to be a necessary byproduct of B.
For example, look at the variety of hair colors and eye colors found in humans!
That's not
necessarily a good example, however. It's not totally clear that hair and eye colour aren't adaptations. They may be have been a product of sexual selection, for instance. Though I can see that they may not be adaptations, as an example of something which
obviously or
necessarily isn't, I don't think they hold up.
Any biological issue involved in the selection of same was long ago buried in the genetic mixing that came with significant means of travel. With perhaps a few exceptions in the deep rainforests or among the Aborigines, we are all 'mutts' whose forebears come from multiple continents.
I don't quite see what this has to do with the point, though. Clearly the selective pressures during our recent evolution, that caused us to be what we are today, were different than the selective pressures that exist now.
But that doesn't suggest that particular traits weren't selected for.
It is surprising to me that people often forget this when discussing evolutionary basis and selection of traits. Some things are neither advantageous nor costly, they just are. Genetic drift can cause some of these "arbitrary" traits to be more or less common without there being any selective pressure based upon the trait.
Definitely. And there are also "spandrels" as Steven J. Gould calls them: traits which, as I said before, are simply the by products of other traits, and not selected for themselves.
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