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Politics : Foreign Affairs Discussion Group -- Ignore unavailable to you. Want to Upgrade?

To: Maurice Winn who wrote (171835)	10/4/2005 12:29:19 AM
From: neolib	Respond to of 281500

On the sexual selection, you left off hermaphrodite as an option. There are various other problems that I didn't go into. Females have a particular issue in that they have two X's. Two of any chromosome is usually a death sentence. Only the X and Y come complete from one parent, the others are split, with half coming from each parent. The problem with having two of any one chromosome, is that whatever the chromosome does, two of them will work twice as hard at, thus killing you in general although some of them like Downs syndrome (extra #21 in general) are survivable. A very high percentage of first trimester miscarriages are thought to be the result of incorrect chromosomes. Anyway, females have two X's, so there is a mechanism which deactivates one of them starting early in embryo development by encapsulating the chromosome in a lipid or protein or something like that. I think this happens in every cell of the female. Partly as a result of this (IIRC) abnormalities with extra X or Y chromosomes are more survivable. So you get things like XXY (Klinefelter syndrome) males. They tend to be a little more female like including higher risk of breast cancer. You can even have more than two X's and live, but the problems get worse. You can have triple X females as well. Oddly enough, single X females exist and have more problems than triple X ones. The single X ones are short and need hormone treatment to help them along, the triple X'ers tend to be tall and mostly normal. Given all that purposeful complexity you described, it would be very surprising if female and male brains behaved the same. There is an area of evolutionary biology which studies "sexual dimorphism". Generally speaking they are looking at differences in physical morphology between the sexes but in humans, we can surely study mental differences as well. Our species is not very sexually dimorphic compared to many other species, which is thought to be due to our being fairly monogamous. Species which are highly polygamous tend to have greater sexual dimorphism, usually seen as physically larger and stronger males, the better to get a harem. There is another bit of info pointing in the same direction. Amongst the great apes, sperm can kind of coagulate in a manner than tends to block the ability of subsequent sperm to get at an egg inside the female. If you look at how effective this sperm coagulation is in different apes (us included) vs. how many sexual partners they have, it is fairly nicely correlated with humans being pretty monogamous and having low sperm coagulation. So biologically, we are fairly monogamous and not very sexually dimorphic. FWIW.