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.
^^^ CB: You might want to remain tactful because it's not clear that you have the best version of basic biology in this argument.
^^^^^
1. Fecundity does not ensure reproductive success.
^^^^^ CB: If one population has significantly higher number of offspring per capita, they have taken a very critical step toward what you refer to as "reproductive success", and biology terms reproductive fitness or differential fertility. It's true that there is a further step , that the "babies" have "babies", i.e. that the offspring be fertile themselves. But , all things being equal, more offspring per capita is likely to produce more offspring per capita in the third generation.
So, "fecundity" may not ensure "reproductive success" or greater fertility of the third generation, but it is a big step toward greater fertility in the third generation.
You try to turn the exception into the basic natural selection rule.
^^^^^^^
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.
^^^^ CB: Yes. You seem to be finally allowing that there might be some genetic basis for inclination to have samesex or othersex ( combined in a complex with culture, of course :>)). The assumption made by Arash and Bodi, I think, is that at the times when the gene frequencies have been established in humans, occasional heterosex produces fewer offspring than frequent/exclusive heterosex, and the latter _do_ care for their offspring to the point of the offspring's own fertile sex acts. In other words, that more heterosex was correlated with more fertile offspring as compared with less hetersex.
It could be the way you say above, but it could be, and seems likely to be, the opposite of what you say above.
^^^^
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.
^^^^^ CB: The trouble with this is that you, throughout this recurrent thread, refuse to acknowledge that the "trait" in question is qualitatively different than any other "trait" with respect to reproduction. The trait in question is the inclination to have absolutely infertile sex ( inclination to homosexuality) or an inclination to have potentially fertile sex. I know you emphasize that individuals now and long ago weren't locked in to rigidly only having infertile or potentially fertile sex, but from the standpoint of biology, the times people spend not having sex that is potentially fertile can make a "differential" that is an advantage/disadvantage. At times of sharp competition especially, the fact that A's are constantly trying to have potentially fertile sex, and B's are only occasionally trying to have potentially fertile sex because much of the time B's are having sex that is not potentially fertile is a differential that is the basis for selection for A's over B's.
To counter this expectation, you must introduce some speculative trait ensemble of "heterosexual inclination combined with an inclination not to raise one's offspring to the offsprings' own fertility", with no evidence for said trait ensemble.
The difference between having exclusive heterosex and occasional heterosex could be enough establish effective differential fertility, absent some countervailing cause, and there is no reason to speculate a countervailing cause as you do.
^^^^^^^
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.
^^^^^ CB: A characteristic can't enhance the reproductive success at a group level without enhancing the reproductive success of some specific individuals.
The phrase "population fecundity at the individual level" is on its face self-contradictory. Perhaps you mean that with two populations, one may have fewer offspring per capita than the other, but the population with the fewer offspring per capita brings more of those offspring to the point of having fertile offspring themselves. Yea. Species with litters can in the long run have less success than a species with single births
But this does get away from the point that holding "child" rearing constant, greater fecundity is likely to mean greater reproductive fitness. You try to turn the exception into the rule on this point.
^^^^^^^^
To be frank, this is pretty basic stuff in evolutionary theory.
^^^^ CB: You are missing some pretty basic stuff yourself here. Other people have studied biology too, you know.
You are sort of elevating unusual exceptions to the general rule to the status of the "rule". In general, greater fecundity is associated with greater reproductive fitness. Then there are some interesting exceptions.
^^^^^
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
^^^^^^ CB: Exactly why you should hold off in claiming that others don't understand basic biology as well as you do.
There aren't really many common-sense claims about evolutionary biology. Common sense believes God made the life forms. What you are saying is that in comparing the phenotypes "predominantly or exclusively hetersexual" and "predominantly or exclusively homosexual", we should not expect the elementary evolutionary biological principle of differential fertility to express itself in the history of our species.