Amaros
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Joined: 7/25/2005
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It is true there is no up or down in evolution - I think a lot of the teleological thinking possibly comes from people who attribute some sort of mystical superiority to humans. Evolutionarily speaking, a succesful species is simply one that isn't extinct yet - a cockroach is every bit as sucessful a species as humans, moreso, if we off ourselves. We have greater cerberal complexity, and that has given us an advantage over a lot of other species whom we've driven into extinction, but it really isn't anything to brag about.
Anyway need, it doesn't quite work that way although you're on the right track in some respects - that diversity will simply tend to occur in a complex species like humans, spread over a wide geographic area, with significant geographcal barriers - that pretty much where racial diversity came in to begin with, a few localized random mutations and a lot of sexual selection among isolated populations, albeit with nough interaction to avoid outright speciation.
Sexual selection is again, the reason behind breast differences - breast size has absolutely nothing to do with breast feeding, so far as I know, beyond certain mechanical advantages perhaps, i.e.,convenience, not efficiency - a preference for large breasts, while not uncommon, is far from universal - so while a trend toward large breastedness has been selected for across cultures, there is no culture where all women are uniformly large breasted - perhaps because while sexual selection among humans can be harsh and agressive, it's fairly rare that anyne is shut out entrely, and for most of human history, enculturation and family connections have tended to outweigh appearence.
I, for one don't really get it - I could really are less how large a womans breasts are, I'm a leg man - but it is programmed in I believe, i.e., a preference for large breasts has been selected for among males to some extent - even my general ambivelence towards breast size doesn't mean I don't notice, it just gets bumped down the list.
Diversity itself, among all species, without the complexity and diversity of human sexual selection patterns, arises primarily from niche shifting - i.e., a certain members of a species adapted to a specific niche ether through a random mutation or sexual selection, exand or shift their range to a slightly differnt niche, and their adaptation path then diverges from the parent species - this can be simply a tolerance for a different temperature range, a different type of forage, a different type of insect, or simply a different method of foraging - these were all factors in how hominids evolved from rodentlike insectivores, and humans from hominids.
There is no overall plan to diversify, but the shotgun analogy still holds up - there has to arise, either through random mutation or sexual selection, some trait that makes it possible for a given genetic line to enhance it's breeding potential by shifting or expanding it's niche - that's your shotgun effect, and it'll keep going as long as there are niches yet to fill
It is interesting that sexual selection can also work against diversity, and in fact it typically does - there is some archeological evidence for a bias against six fingered humans (polydactyly) - a not uncommon random mutation that is neither partiularly beneficial nor particuarly detrimental from a purely morphological standpont - but there are no cultures where polydactyly is anymore common than any other culture - .i.e., it's fairly evident that this particular trait has been selected against across all cultures. In recent years, with less a less profoundly superstitious zeitgeist at work, polydactyly has begun to run in certain families, founding what might be called a polydactylic human varient - and given enough generations - a couple of hundred thousand perhaps - it might eventually drift into the general population after being deliberately excised for the last couple of hundred thousand generations.
Sexual selection tends to homogenize, according to current notions of physical beauty and/or other adaptive charateristics deemed desireable by mass culture, or species specific traits.
Still, the babe married to the wealthy businessman might well be raising the children of the poolman - there are a number of levels, divisions and degrees to what is or is not sexually desireable to humans, and that itself can change over time - another force adding to the shotgun effect.
Finally, should a highly variable species like humans arise - which it did - that propensity for diversity in both morphological and psychological traits can be advantagoeous under changing conditions by countering overspecialization and homogneizing effects - the DRD4 - 7R alleles occurs in a number of variants, several of which have been identifed as being related to both ADHD, and '"novelty", or thrill seeking personality types - it's speculated that random mutations in these alleles may have been of great significance when they occured, approx. 40k y.a. - at that time individuals possessing these variations may have had significant sexual selection advantages over more "socilized" personality types - nowadays, we medicate them.
Actually, it would be interesting to see if these DRD4-7R varients are more common among BDSM afficionados - they almost certainy are among other extreme sports enthusiasts.
http://www.pubmedcentral.gov/articlerender.fcgi?artid=117557
< Message edited by Amaros -- 4/17/2006 8:51:27 AM >
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RE: Evolution Thoughts - 
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