vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn) (03/11/88)
In article <13400@sri-unix.SRI.COM> maslak@unix.sri.com (Valerie Maslak) writes: >Sigh. I didn't say height was a sex-linked genetic characteristic. >Although some men here seem to be arguning that it is !!! >I MEANT that the much-above-average-height-and-build women were >discriminated against in the selection process...not because they >weren't "the fittest" as some have argued that they are, but because >the male-imposed norms for female desirability have made them less >preferred as mates. > >This is getting tedious. Yes, this seems to be the only possibility. Nor should we be surprised: in classical evolutionary theory it is described as "sexual selection." It is used to describe various and sundry typcially male charactersitics as peacock tails and other silly and seemingly useless features. While I've read about this, it has never made any sense to me. I'm cross-posted to sci.bio. Could someone please explain the theory of sexual selection to us, try to justify it (I've never believed it, despite the evidence), and relate it to common sexual dimorphism like height, etc.? O----------------------------------------------------------------------> | Cliff Joslyn, Professional Cybernetician | Systems Science Department, SUNY Binghamton, New York, but my opinions | vu0112@bingvaxu.cc.binghamton.edu V All the world is biscuit shaped. . .
g-rh@cca.CCA.COM (Richard Harter) (03/11/88)
In article <913@bingvaxu.cc.binghamton.edu> vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn) writes: >Yes, this seems to be the only possibility. Nor should we be surprised: >in classical evolutionary theory it is described as "sexual selection." >It is used to describe various and sundry typcially male charactersitics >as peacock tails and other silly and seemingly useless features. While >I've read about this, it has never made any sense to me. >I'm cross-posted to sci.bio. Could someone please explain the theory of >sexual selection to us, try to justify it (I've never believed it, >despite the evidence), and relate it to common sexual dimorphism like >height, etc.? Let me make it simple, and talk about buying apples for a moment. When you eat an apple you want one that is ripe, does not have worms in it, is not spoiled or bruised, and so on. So what do you do when you go to buy apples -- you look for one that is red, looks juicy, and is unblemished. The vendors of apples want to sell you apples, so they take due care to provide apples that meet these criteria. Note that these criteria don't actually tell you that this apple is going to be good eating. Note also that the vendor of apples is not trying to supply you with good eating, she is trying to sell you what you will buy. Even so, you will tend to select the really red apple unless you think about it, and the vendors of apples apply artifice to make there apples redder than nature intended. Now you, as a clever human being, can figure out what the vendor is up to, and can figure out what it is that you actually want. But an animal is not so clever, and relies on built in cues to make these selections. Success in breeding goes to those males who best meet the built in cues. Now these cues are often things like redness in apples -- whence, the redder the better. Males who most markedly satisfy the selection criteria are most likely to get selected. This gets inherited, so the selection process drives steadily towards emphasizing any feature that is used as a cue. NOTE THAT IT IS THE FEMALE THAT SELECTS. Females select, fundamentally, because they make the big investment in offspring. Since they do the selecting, the selection process is not as demanding on them (except that they must provide reliable fertility cues). This is the general theory. Human beings, at this point, are in a special category; our sexual selection process does not match our evolution -- we have mixed it all up by having intelligence and civilization. -- In the fields of Hell where the grass grows high Are the graves of dreams allowed to die. Richard Harter, SMDS Inc.
vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn) (03/11/88)
In article <25443@cca.CCA.COM> g-rh@CCA.CCA.COM.UUCP (Richard Harter) writes: >Let me make it simple, and talk about buying apples for a moment. When >you eat an apple you want one that is ripe, does not have worms in it, >is not spoiled or bruised, and so on. So what do you do when you go >to buy apples -- you look for one that is red, looks juicy, and is >unblemished. The vendors of apples want to sell you apples, so they >take due care to provide apples that meet these criteria. Ah, I'm begining to see some parallels to other problems. Perhaps this is essentially a problem of evidence. The female has a theory that certain characteristics (e.g. big tails, height, bulk) are good evidence for genetic fitness. Let us presume that originally this is justified. Then the "battle of the sexes" kicks in, and the males try to increase the evidence, and don't give two hoots about the continued validity of the evidence for the fitness. The poor females are stuck, without intelligence, and then a natural positive feedback process ensues, resulting, ultimately, in the demise of the males whose exagerrated sexual characteristics finally become de-selective (e.g. tails so big they can't even walk anymore) for that individual (although still highly sexually selective). >This is the general theory. Human beings, at this point, are in a >special category; our sexual selection process does not match our >evolution -- we have mixed it all up by having intelligence and >civilization. But presumably the above scenario was in effect throughout homonid evolution, and modern dimorphism is the "residual" effect of that. And even though humans, through our intelligence, are free to ignore sexual selection pressurres, I think we'd all agree that they are still *frequently* adhered to (e.g. frat boys/girls :->). O----------------------------------------------------------------------> | Cliff Joslyn, Professional Cybernetician | Systems Science Department, SUNY Binghamton, New York, but my opinions | vu0112@bingvaxu.cc.binghamton.edu V All the world is biscuit shaped. . .
kevin@chromo.ucsc.edu (Kevin McLoughlin) (03/17/88)
In article <914@bingvaxu.cc.binghamton.edu> vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn) writes: >But presumably the above scenario was in effect throughout homonid >evolution, and modern dimorphism is the "residual" effect of that. With the proviso that sexual selection works in two ways: 1) females create a selection pressure for males to look like they can provide good genes and (in hominids maybe also) help and companionship in the hard work of raising a primate child to adulthood 2) males compete with each other for the sexual favor of the females, which creates another selection pressure on males for traits that are important in this male-male competition process (dog-and-pony-show, really). A lot of (2) may be why males are usually bigger than females in mammals: in some species (deer) they fight, in other species they just try to scare and impress each other with a mouthful of big teeth (chimps, baboons), colorful or hairy accouterments to the body (lions, orangutans, human males), aggressive show-offy behavior acting as IF they're the meanest SOB around (most mammalian males), etc. So dimorphism MAY be a result of direct female choice for big males but PROBABLY is more likely a result of the games males play with each other. ----------- Susan Nordmark Internet: kevin@chromo.UCSC.edu UUCP: ...ucbvax!ucscc!chromo.kevin Santa Cruz, CA
jnp@calmasd.GE.COM (John Pantone) (03/18/88)
> So dimorphism MAY be a result of direct female choice for big males > but PROBABLY is more likely a result of the games males play with > each other. > > ----------- > Susan Nordmark > Internet: kevin@chromo.UCSC.edu > UUCP: ...ucbvax!ucscc!chromo.kevin Santa Cruz, CA I would guess this is at least partly true, but my feeling is that the marked dimorphism in humans is the result of physical adaptation to social roles. In most primitive societies (pre-agricultural) women are gatherers and men are hunters (and to a lesser extent women "hide" with the children and men go out to confront the "enemy"). The women care for the children and gather food (the most reliable food source) and men hunt (less reliable but greater quantities when they are successful). The body forms of present day humans still reflect this adaptation rather well, men are relatively strong and "brawny", but tend toward lower endurance, the women are less muscular but tend to be more able to carry out low-level activity for far longer than men. Actually this endurance thing is extremely interesting in its own right. There are really only 2 animals on earth which hunt by out-enduring (running down) their prey - humans and canines. This form of hunting is called "Cursorial" (runners) and relys on the exceptional endurance of humans and dogs compared to virtually any other animal. So - the difference between the endurance of men versus women is only relative. Please - no flames - I am well aware of the fact that this is simply an overall tendency - there are plenty of "big" women and "small" men but they are exceptions. -- These opinions are solely mine and in no way reflect those of my employer. John M. Pantone @ GE/Calma R&D, 9805 Scranton Rd., San Diego, CA 92121 ...{ucbvax|decvax}!sdcsvax!calmasd!jnp jnp@calmasd.GE.COM GEnie: J.PANTONE
g-rh@cca.CCA.COM (Richard Harter) (03/19/88)
>I would guess this is at least partly true, but my feeling is that the >marked dimorphism in humans is the result of physical adaptation to >social roles. In most primitive societies (pre-agricultural) women >are gatherers and men are hunters (and to a lesser extent women "hide" >with the children and men go out to confront the "enemy"). The women >care for the children and gather food (the most reliable food source) >and men hunt (less reliable but greater quantities when they are >successful). The body forms of present day humans still reflect this >adaptation rather well, men are relatively strong and "brawny", but >tend toward lower endurance, the women are less muscular but tend to >be more able to carry out low-level activity for far longer than men. Unlikely -- it is probably more the other way around -- social roles adapt to physical differences. Primate dimorphism is general in the great apes and rather old -- it goes back a long ways. One has to consider the possibility that dismorphism is (at this point) simply built in. Organisms are not infinitely malleable; selection works with existing mechanisms. It may, in effect, be hard to select against dimorphism once the mechansim is thoroughly in place. Another factor that should be considered is that selection in humans and pre-humans operated differently than it does in baboons, for example. In baboons a male gets to breed if it is an alpha male. Selection is strong for alpha male traits. In humans a male gets to breed if he can find a mate. Most males get to breed; only the marginal ones do not. Selection is much weaker and is mostly negative selection against non-survival traits and those traits that lead males either not to breed or not to be an acceptable mate to any female. A major class of such traits is 'social acceptability' -- any individual that cannot be accepted in the tribe has low prospects for being part of the breeding pool. In a general way there may be something to what you say -- social roles can condition selection. The problem with that idea is simply that it is easier to alter social roles to fit physiology than it is to alter physiology to fit social roles, in humans, at least. -- In the fields of Hell where the grass grows high Are the graves of dreams allowed to die. Richard Harter, SMDS Inc.
rdh@sun.uucp (Robert Hartman) (03/19/88)
In article <2686@calmasd.GE.COM> jnp@calmasd.GE.COM (John Pantone) writes: > >I would guess this is at least partly true, but my feeling is that the >marked dimorphism in humans is the result of physical adaptation to >social roles. I don't think that social roles are sufficient to account for the dimorphism, in our secondary sexual characteristics. I suspect that a more likely cause is that in the environmental settings in which we began to diverge from the other great apes, there was a physical advantage to these differences for child-rearing. -bob.
heather@blia.BLI.COM (Heather Mackinnon) (03/19/88)
There have been many human societies with baboon-style alpha male mating patterns. The early Hebrews practiced polygamy. The Egyptians practiced polygamy as did the early Greeks (concubinage). Polygamy has been practiced until recent times by American Indians, in the mideast, by Mormons in the U.S., throughout the Orient and by various African tribes. In fact, I can't think of any non-European culture that has exclusively practiced monogamy. In hunter-gatherer and belligerent societies, the death rate among adult males would be expected to be higher than among adult females. In a subsistence culture, you wouldn't want to waste any breeding females; too few babies survive to adulthood. This leads to an interesting question: when did the move towards monogamy happen and why? Did it happen when agriculture replaced hunting and gathering? Did it happen with the growth of cities? Did it happen when the male and female populations became more even? Does it have anything to do with Christianity? (In India, Hinduism permits polygamy, but Mohammedism forbids it.) In any case, our human history of polygamy would explain high levels of sexual dimorphism in humans.
vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn) (03/20/88)
In article <4368@blia.BLI.COM> heather@blia.BLI.COM (Heather Mackinnon) writes: >There have been many human societies with baboon-style alpha male >mating patterns. The early Hebrews practiced polygamy. > [etc. interesting comments on *polygamy* ] Is it wise to identify alpha-male "harem" style breeding behavior with human polygamy? My impression is that in *large* cultures that *actively* practice polygamy (e.g. Arabic, African Moslem, ruling out Mormons as a "deviant" group (I can see those Mormon flamers getting going)) that it is not required, and that most all men have at least one wife, while the wealthy few can afford more than one. Two or three is a bit more common, but in, say, elks, the harem sizes can be more than a dozen. O----------------------------------------------------------------------> | Cliff Joslyn, Professional Cybernetician | Systems Science Department, SUNY Binghamton, New York, but my opinions | vu0112@bingvaxu.cc.binghamton.edu V All the world is biscuit shaped. . .
g-rh@cca.CCA.COM (Richard Harter) (03/20/88)
In article <4368@blia.BLI.COM> heather@blia.BLI.COM (Heather Mackinnon) writes: >There have been many human societies with baboon-style alpha male >mating patterns. [Examples of polygamy deleted.] Not the same thing. Human polygamy is tied to support. The male with several wives must be able to support them all. In these societies I believe you will find that polygamy was pretty much restricted to a relatively wealthy minority, with most people being monogamous. In baboons, et. al. the alpha male does not support the females and the young. Only the alpha males breed. The situations are quite different from a selection viewpoint. >This leads to an interesting question: when did the move towards monogamy >happen and why? Did it happen when agriculture replaced hunting and >gathering? Did it happen with the growth of cities? Did it happen when >the male and female populations became more even? Does it have anything >to do with Christianity? (In India, Hinduism permits polygamy, but >Mohammedism forbids it.) I'm a little skeptical about this idea that the male and female populations were ever out of balance as a regular thing -- on one hand the males lead riskier lives, on the other hand females died with great regularity in childbirth. I would phrase the question differently, as "when did polygamy become unacceptable?". I rather suspect that wide spread polygamy came into being with agriculture, just because it became economically feasible (i.e. wealth suplus and larger, more differentiated society.) It is an interesting question, though. -- In the fields of Hell where the grass grows high Are the graves of dreams allowed to die. Richard Harter, SMDS Inc.