Re: buns vs brains

phil osborn (
Sat, 24 Jul 1999 14:30:24 PDT

This is a VERY large topic. One of the more interesting recent pieces of info to come out of the evolutionary biology camp is the following: It seems that men have a slightly larger investment in having large birth weights, as it gives their particular genetic baby a slight advantage, whereas women have a slight investment in having lower birth weights, as it increases the likelihood of their own survival post partem, and thus that of their future children. Thus it came as no great surprise to discover that there are actually genetic mechanisms present in the sex chromosomes of both sexes that are in a continuous war for the advantage of the respective sexes. The male program tries to prevent early delivery or postpone it as long as possible. The female program tries to encourage a slightly earlier delivery.

There is the general fact that is perhaps unique to humans that the size of the infant cranium is just about at the physical limits of the female pelvis. Much bigger and women wouldn't be able to walk. This may be the major reason why human brain size and probably general intelligence apparently reached a maximum some tens of thousands of years ago. Neoteny can only be pushed so far. (I'm not sure whether humans tend to have more premees than other species, but I would suspect that to be the case.)

There is also the fact that the genes necessary for intelligence are not present on the male sex chromosome. Thus, men inherit their intelligence exclusively from the mother, or so the evidence points so far. Women, on the other hand, inherit from both parents. However, in most primitive societies, a smart daughter is competition, whereas a smart son is an asset, so this gives women an incentive to mate with dumb jocks, which reduces the likely intelligence of their daughters while having no effect on the intelligence of their sons. There is a secondary factor that doubles this effect, as well. It turns out that intelligence as well as muscles and good health are all assets to survival. A smart male may make it in spite of otherwise poor genes. Thus, mating with an obviously smart male further reduces the woman's own chances of producing smart, healthy sons.

Bottom line: bio-genetic problems on the female side are probably the reason why genetic human intelligence has stopped evolving.

>From: Spike Jones <>
>Subject: Re: buns vs brains
>Date: Tue, 20 Jul 1999 21:12:07 -0700
> > Don't get [phil osborn] started. Most women seem to have an
> > underlying...[snip]
> > ...rant, rant, rant - you can fill in the blanks from here, as I know
> > most
> > men have had these experiences...
>This whole thread went off in a direction I never intended. Ah, the magic
>of a web discussion! {8^D Perhaps I should have specified I meant
>chimps. Less emotional baggage [that we all carry] from unsuccessful
>relationships, broken hearts, etc. Humans are too complicated.
>That said, what I am really looking at here is the implications of mating
>behavior to evolution, the future of the race, etc. Consider the first
>humans vs the very similar chimps. The first humans likely had the
>mutation of a straight leg: they could lock the knee and walk on two
>legs much more easily than the chimps. This mutation freed the hands
>to manipulate objects. The critical factor is that being able to
>objects caused the smarter protohumans to have a survival advantage
>over dumber protohumans, whereas it is not clear to me that the smarter
>chimps have any real reproductive advantage over dumber chimps.
>I am way out of my field here, so biologists, please help me out.
>This factor would cause the humans to gradually become smarter,
>as a group, whereas the chimps went right along eating termites
>and doing their chimp things. Isnt that kinda the way it works?
>Nowthen, fast forward to present day. Humans have been intelligent
>now for at least 50k years. We have developed the technologies
>critical to our survival. What I am driving at with the whole brains
>vs buns thing is that there may have been subtle influences that
>slightly favored brains, but this influences were subtle indeed.
>Now however, it seems society has created a system which gives
>an *enormous* reproductive advantage... to being stupid! Our
>welfare system encourages overbreeding by those who cannot
>take care of themselves, overbreeding by those who put their
>faith in a church that urges them to be fruitful and multiply,
>overbreeding by those who are drug addicts, etc. [Natasha
>*almost* went here I think with her carefully worded comments
>on teenage pregnancies.]
>Those who you and I might agree are the most fit for the future
>reproduce only modestly, if it all. My burden is this: all those
>influences that shaped humankind in past millenia were subtle.
>Modern influences by comparison are overwhelming and the
>implications to our species profound. spike

Get Free Email and Do More On The Web. Visit