"I'm not assuming every trait must benefit reproductive fitness, they very well could be neutral to it, I am assuming that a trait that has a net NEGATIVE EFFECT on reproductive fitness should fade out of the population over time."
I was careful to specify reproductive fitness over fecundity in my comment but even Boddi's comment isn't inaccurate, traits that reduce fecundity are not evolutionarily neutral, they have to be balanced out in some way to provide overall reproductive fitness, which is all you've managed to elaborate on below.
In fact the variety of explanation you cite below is exactly of the kind biologists have used in attempts to resolve the evolutionary puzzle of human homosexuality. I already mentioned and cited a super-individual case, the study on female relatives of gay men being more fertile. Though this is only a partial explanation as the particular level of fertility studied doesn't make up for the loss in the gay men's offspring, it is an explanation that nevertheless tries to place homosexuality in an evolutionary context. Touting the explanations below doesn't support your position that there is no need to explain homosexuality in evolutionary terms, they undermines it.
Arash
-----Original Message----- From: lbo-talk-bounces at lbo-talk.org [mailto:lbo-talk-bounces at lbo-talk.org] On Behalf Of Miles Jackson Sent: Thursday, December 01, 2005 10:35 PM To: lbo-talk at lbo-talk.org Subject: Re: [lbo-talk] Re: Instinct
boddi satva wrote:
> C. Miles,
>
> No evolutionary biologist would argue that traits which may tend to
> reduce population fecundity are evolutionarily neutral.
>
I'm trying to think of some way to be tactful here, but I'm having a hard time. I know the claim you make above seems obvious, but like many common sense ideas, it is contradicted by well-supported scientific theory.
1. Fecundity does not ensure reproductive success. If people (say, oh, I don't know, people who only occasionally has heterosexual relations, like most gays and lesbians) have offspring and care for them effectively, their reproductive success could in fact be higher than people who kick out lots of babies but don't effectively raise them. Evolution does not select for fecundity; it selects for reproductive success. Important distinction.
2. Traits do not come as independent "packets" that all work independently to increase or decrease reproductive success. A particular trait may be genetically linked to another ensemble to traits that increases reproductive success; thus the existence of some trait that appears to "reduce population fecundity" analyzed in isolation is in fact part of the constellation of traits that all together enhance reproductive success.
3. The idea that natural selection only works at the individual level (if traits undermine an individual's fecundity, they will be selected out of the gene pool) is mercilessly ridiculed by serious evolutionary theorists. A characteristic could enhance the reproductive success at a super-individual level (group, subspecies), and thus survive in a species, even if it reduces population fecundity at the individual level.
To be frank, this is pretty basic stuff in evolutionary theory. I'm just an interested bystander (my main academic training is in psychology and sociology, not biology!); I'm sure a full-blooded evolutionary theorist could add dozens of other examples to my list. In any case, I hope this makes it clear why your common-sense claims about evolution are dubious.
Miles ___________________________________ http://mailman.lbo-talk.org/mailman/listinfo/lbo-talk