I think this is part of it. The proportions and appearances of the “Ideal Woman” have shifted markedly over centuries, even within the past 80 years. Natural selection can’t begin to account for rapidly shifting cultural tastes, thus explaining the rise of cosmetic surgeons. The figure of the Rubanesque woman of the Renaissance is quite different from the 1920s flapper, the “heroin chic” of the 1990s, and the aerobicized/surgically enhanced gal of today. How any of this fits into evolutionary-driven theories is beyond me, but I’m sure it wins federal research grants.
I’ve read evolutionary psychologists’ claims that men desire women who can produce offspring that will have a competitive advantage, but many men, at least when they’re young, seem entirely focused on the act of copulation. They’re looking for a great bod paired with a great face–for their enjoyment, not for the competitive advantage of their future kids. Indeed, the notion of siring any offspring is the last thing on their minds. I think this theory assumes way too much conscious choice (or determinism), while overlooking the importance of pleasure and ego/id.
Not sure how to explain the female drive, but a lot seems generational.
What you’re missing here is that “men desire women who can produce offspring that will have a competitive advantage” does not entail that their conscious motivation isn’t that great bod and sheer pleasure. I want to have sex with gorgeous women because it’s pleasurable, not because I want to have lots of kids. But the underlying reason for why I want to have sex with gorgeous women is that having that desire makes me more likely to have lots of kids. When evolutionary psychologists say, “men desire women who can produce offspring that will have a competitive advantage” they don’t mean that guys go around saying to themselves, “Wow! She looks like she’d produce healthy kids!” but rather that the women men tend to desire most (because of their full breasts and small waists) are those that in fact will produce healthy kids.
It’s a subtle point, but I believe the storage capacity of the breast influences its rate of milk production. If frequent and periodic feeding and emptying occur, then breast size is not so important. However, irregularity in feeding and emptying can lead to pressure in the alveolar tissue in the breast, a function of breast volume, wich essentially sends a signal to limit milk production. I cannot remember where I saw the cite (I’m looking), but I think the gist was the larger breast has, on average, greater storage capacity and will continue producing longer than the smaller breast because of this storage capacity.
Also, on the subject of fat, fat content in milk is also influenced by this pressure feedback system. Hence, women with more capacious breast may have fattier milk, on average. Having more fat in the breast doesn’t hurt, in this arrangement. In our well-fed society, these distinctions are completely unimportant. In the days of our ancestors, though, these small differences could perhaps have tipped the balance between death or survival in times of want and turmoil.
> . . . the “heroin chic” of the 1990s, and the aerobicized/surgically enhanced gal
> of today . . .
Not only is much of this difference driven by mere fashion, but I’ve got to wonder if these differences in fashion exist anywhere except in the heads of a few fashion designers, TV producers, magazine editors, and other self-appointed arbitrators or current taste. I wonder this especially because of the distinction made here between the decade of the 1990’s and “today.” Wait, are you telling me that there has been a big shift in the desires of men in maybe ten years? Does this really have anything to do with any changes in what men want over that decade, or does this mean nothing except that these influential fashionistas have decided that at one point the hip look will be drug-addict thin and the next the look will be pumped-up? I look at this as being like the clothes worn at the big Paris/Milan/New York fashion shows - hardly any of which will affect what nearly all women will actually wear.
Larger, fuller, rounder, doesn’t matter what you call them, they’re not better milk producers. ( The exception being hypoplastic or “tubular” breasts, which are a medical condition wherein the milk glands and ducts themselves are underdeveloped.) Larger breasts may be better milk storers, but that simply means our babies eat less often. However, large breasted women have more trouble with latch-on, cracking and infection, so there you go. For a cite: copy and paste this: http://www.007b.com/breast_size_breastfeeding.php into your browser, as it does contain pictures of nude, non-erotic breasts.
Also, the external hip measurement does not correlate with the internal pelvic measurement. “Breeding hips,” as my grandmother fondly calls them, do NOT actually indicate that there is enough room for a baby to pass through in childbirth. My own mom, who definitely “Got Back” as the artiste once spoke, has a rather small internal pelvic measurement. They told her I was going to be a C-section, and only her damned stubbornness and going AMA got me out vaginally - plucked out by forceps, with a really squished head and a dislocated soulder.
Bust to waist ratio has indeed been correlated with 30% higher estradiol levels, which may indicate a greater ability to get pregnant by threefold. A low waist to hip ratio is associated with higher levels of progesterone. The article also points out that “some non-Western societies do not use the same measurements of female attractiveness. In cultures which value large women, size may be a more important indicator of nutrition and health and therefore fertility, she says.”
There have been dozens of studies which all confirm that men find women with a waist to hip ratio of 0.7 to be the most sexually attractive. There are several studies which show similar results for lesbian and bisexual women. Google waist to hip ratio attractiveness for cites.
Hmm…I’m not a physiologist, so you may well be right, but I’d like to see a cite on that. My understanding was that the non-parturient size of the breast has little to do with actual milk storage capacity (hence the swelling of breasts, particularly noticable in less-endowed women, during pregnancy), but again, I’m not an expert on the female anatomy; just an enthusiastic amateur.
I’ve never understood this line of reasoning. If the big-tail peacock can run at the same speed as the small-tail peacock, then (in the area of running, at least) it is equal. It is not superior for doing it despite a handicap, it’s the same. Or you could turn it around: Presumably, that big-tail peacock must have stronger muscles, or some other adaptation, to make up for that parachute it’s dragging. Could you not say that the smaller-tailed peacock is superior, because it manages to run just as fast despite the weaker muscles?
The question, of course, with sexual selection, is why does the other sex prefer the apparently neutral or detrimental trait? It isn’t necessary to suppose a “most fit handicap”, or the like. The simple answer is that there’s advantage in preferring what everyone else prefers. Suppose, for instance, that you had a peahen with a bizarre fetish for short-tailed peacocks (and suppose also, of course, that this fetish, or at least a prediliction towards it, is genetically heritable). She goes out and finds the shortest-tail peacock she can find, and mates with him. Of her chicks, about half are going to be males, and because of their father, they’re likely to have shorter tails than the average peacock. Now, unless they can find more peahens with that fetish (unlikely, since most hens prefer big tails), those cocks are going to have a harder time finding mates, and will on average have fewer chicks. So that fetish peahen is going to have fewer grandchicks, on average, than other peahens, so the gene for that fetish is going to diminish and eventually disappear from the population.
Note that this mechanism can occur for any trait at all, so long as the selective pressures against that trait don’t overwhelm it. It can get started just by random variation, and once that happens, it’s reinforced. There’s not necessarily any particular reason why that particular trait was chosen: Maybe it does lead to easier childbirth, or some other obvious advantage, but maybe it’s just what the opposite sex happens to like for no particular reason at all.
Well, it’s been a while since I read about this, but with some concerted searching I think I’ve found something related to what I was talking about. I cannot for the life of me find the original article, and so this will have to suffice for now:
A page alluding to the storage issue, and also the relation of production to fat content.
I believe this is the primary source for some of the relevent points in the above page. A germane excerpt:
I’d pretty sure this must have something to do with the cite which I remember reading, but now cannot find. I’ll keep looking, but this is the best I can do right now.
I should have probably qualified my earlier post by stating that the idea is a hypothesis, rather than an accepted theory (and hence is not included in elementry textbooks on zoology). Zoology being a mostly observational science, it takes an exceptional preponderance of evidence before a theory is accepted into the mainstream (Darwin’s researches were nothing short of astonishing in their breadth and depth) and a mechanism that only shows up as a statistical nudge is going to require more than a few studies to validate it.
However, it is a mechanism by which the mean of a population can be pushed toward adopting a detrimental trait. Some traits, like the giraffe’s elongated neck, are obvious tradeoffs–longer nerves, more difficult balance, extra musculature against access to greater resources–and others are apparently neutral, like the color of plumage of various parrots. But the idea that a species would adopt a trait that is manifestly detrimental, without any outside pressures, is so confounding that it questions the very premises of natural selection. Once such a trait has been adopted, ornimental reproductive pressures might serve to exaggerate it (to the very limits of organism fitness), but something has to bring it into the phenotypical mainstream to begin with.
Your example of the short-tail fetish highlights the difficulty of introducing an extreme variation in characteristics into a population; if it is too far outside the norm, it will wither away, or perhaps break off into a seperate population, but will not influence the main pool of genes, unless it has an effect on reproductive fitness. Normal variation without outside impetus should keep a population centered roughly around its mean, allowing for random drift. Outside influences that affect fitness should prevent charateristics from drifting to detrimental extreme. A mechanism is thus (presumably) required to push toward ornimental excess.
And so, the mechanism put forward is that the ability to display ornimental excess indicates greater “wealth”, i.e. an ability to squander resources and spend more time on mating rituals at a cost of spending resources on organism survival. Peacock fans, overlarge genitalia, and complex mating rituals demonstrate that a creature is so fit in its environs that it doesn’t need to spend every waking moment searching for food or hiding from predators. Such a creature is likely to have genes that will better enable its offspring to have a life of Riley and/or attract other well-fit mates.
This is all bearing in mind, of course, that it is the individual genes (or partnerships thereof), and not the organism as a gestalt, which are determining fitness, based on the ability to make more copies of themselves. The genes themselves may have competing interests which lead to compromises in the resultant organism, and since they don’t actually have cognitive understanding of the intent of other genes (despite the whole “selfish” metaphor) they might drive an organism or entire species into an evolutionary dead-end in furtherence of their individual goals.
YMMV, of course. Not every evolutionary zoologist and paleontologist agrees with the concept (I believe the Gould camp suggested several alternate mechanisms which better supported his punctuated equilibrium hypothesis) and the evidence is so subject to interpretation that it’s impossible at this point to make a definitve statement on the issue, but it seems to me the most likely hypothesis for orimental excess in natural selection.
BTW, disclosure time: I’m not a zoologist or a paleontologist, and although I’ve read through the standard texts and have delved, but slightly, into the technical literature on the topic, I don’t claim to be an authority on the subject. If you’re interested, I’ll see if I can dig up some scholarly citations on the topic, but it’s been a couple of years since I’ve really read this subject, and if someone has a more extensive background or deeper understanding, by all means feel free to correct, debate, or condradict my statement on it.
You are making the assumpiton that the trait in question is “manifestly detrimental”; an alternate epxlanation which doesn’t req
This is all bearing in mind, of course, that it is the individual genes (or partnerships thereof), and not the organism as a gestalt, which are determining fitness, based on the ability to make more copies of themselves. The genes themselves may have competing interests which lead to compromises in the resultant organism, and since they don’t actually have cognitive understanding of the intent of other genes (despite the whole “selfish” metaphor) they might drive an organism or entire species into an evolutionary dead-end in furtherence of their individual goals.
YMMV, of course. Not every evolutionary zoologist and paleontologist agrees with the concept (I believe the Gould camp suggested several alternate mechanisms which better supported his punctuated equilibrium hypothesis) and the evidence is so subject to interpretation that it’s impossible at this point to make a definitve statement on the issue, but it seems to me the most likely hypothesis for orimental excess in natural selection.
BTW, disclosure time: I’m not a zoologist or a paleontologist, and although I’ve read through the standard texts and have delved, but slightly, into the technical literature on the topic, I don’t claim to be an authority on the subject. If you’re interested, I’ll see if I can dig up some scholarly citations on the topic, but it’s been a couple of years since I’ve really read this subject, and if someone has a more extensive background or deeper understanding, by all means feel free to correct, debate, or condradict my statement on it.
What the heck…? Ignore that last post. This is what was supposed to have been submitted:
It sounds like you are pushing awfully close to advocating the notion of orthogenesis…
Sexual selection is really just a special class of natural selection. A species can just as easily be evolving showy sexual displays as indicators of fitness, not as a deleterious advertisement which necessarily puts the individual possessing them at risk. Thus, the strongest and “bestest” peacocks would (should) have the showiest tails. The tail is not a diversion of resources, it’s a primary resource in and of itself! Only at extreme sizes would the tail itself become disadvantageous, which would result in stabilizing selection to maintain it at a workable size within the population (i.e., those individuals who happen to be “gifted” with a true excess of tail feathers would likely find themselves as lunch, rather than a real ladies’ bird).
This is probably not the place to get into this, but Dawkins proposed his “selfish gene” theory, not as an evolutionary panacea, but to specifically explain the evolution of altruism, and The Selfish Gene was essentially a treatise countering the concept of group selection. Selection operates at muiltiple levels, from genic to individuals to species. The selfish gene is a metaphor to aid understanding, not something which was meant to be taken literally.
There are problems with Dawkins formulation of genic selection as the only (or even primary) locus of selection. Just as much has happened in evolutionary biology since Darwin published Origin, much has happened since Dawkins published The Selfish Gene. See, for example, here for a critique of genic selection and a proposal which incorporates developmental aspects into overall evolutionary theories.
Punctuated equilbrium likely has little to do with the issue. PE is a theory which serves to introduce a catastrophic component to uniformitarianism, and further serves to explain the appearance of the fossil record as more than mere incompleteness, but as a natural consequence of the mechanisms which result in speciation.
6’2, 180 lbs. checking in. My son is 6’0, 170, daughter 5’6, 100. We’re real people, we didn’t work to get this way. There are many just like us. Runway fashions are meant for those who can wear them, just like Ferrari is meant for those who can afford it. I’m sorry there are those who make themselves unhealthy to fit a certain image.
I get the impession we’re debating whether the Pope is Catholic or Polish. I agree that the display is an indicator of fitness, but by “squandering” resources on maintaining, in this case, an enormous tail and the subsequent handicap to the bird, it demonstrates how otherwise fit it is. In some cases, like bright plumages that don’t act as camouflage, the direction that the species evolves is essentially immaterial; blue head, yellow wings or red head, green wings; either is as likely as the other and subject to random drift. But in the case of the peacock’s tail, it had to start out giving away more resources and accepting more risk; therefore, there should be some compensation, some impetus for it being selected more often that not. As you state, sexual selection is a subset of natural selection, but as with other measures of reproductive success, ornamental excess should correspond, at least initially, with some other aspect of fitness. Once established, of course, then it can be “assumed” as an indicator of fitness and exaggerations can fool potential mates as to the extent of fitness, leading to a pressure to evolve more and more exaggerated ornaments.
I understand, but one can look at the genes for the phenotype of the tail as being “selfish” as compared with other genes, riding on the back of genes that otherwise promote reproductive fitness and ultimately becoming an external marker of those genes, or as you put it, an indicator of fitness. Dawkins goes into further detail on this in The Extended Phenotype, which I imagine you’ve already read, and while I think he overreaches in a few places, the basic theory seems sound.
I agree that selection can also take place on the individual level. I’m a little more dubious about selection at the species level–what “motivation” would drive an entire species, en masse, toward a particular evolutionary path?–but I’m willing to keep an open mind about it. Thanks for the cite; I read the intro and plan on reading the body shortly.
I didn’t mean that PE actually had much of anything to do with the topic at hand, just that Gould (or rather, evolutionists of Gould’s camp) had put forth some theories on the purported rapid phenotypical changes in species to explain PE that also could be considered alternate or competing theories. I was just illustrating that it isn’t a set-in-stone idea but rather a hypothesis (one of many) to explain the otherwise strange adoption of exaggerated features.
It’s an interesting topic, and as I said, I’m not an expert. Perhaps I should start another thread on this. Anyway, thanks for responding so cordially and providing that cite.
but what makes you prefer any particular women has a “great” bod and face? A frog would prefer another frog, a gorilla another gorilla. You are programmed either through conditioning or instinct to choose big bazookas, tight derriere, and clean skin. The question in this thread is whether that preference is instinctual, and if so whether the instinct arose because the traits have some evolutionary advantage. Some traits like the peacocks tail do not appear to have any evolutionary adavntage, and are usually thought of as arising from sexual selection, which can be blind and directionless.
one theory which has done the rounds is that a big tail peacock is announcing that he is “better”, as he must be also be more resistant to disease and parasites. Still tentative though
"Moller’s theory was that these ornaments signal different aspects of the male’s quality to a female.
Indeed, the results from the study seem to support his hypothesis. He and Petrie discovered that the condition and length of the peacock’s tail was related to the production of B-cells, and the size of the eye spots to T-cell production"
“Our main finding is that females are looking at different aspects of a male’s immune competence,” said Moller. Males, in effect, are walking billboards advertising their health and status."
> Runway fashions are meant for those who can wear them, just like Ferrari is
> meant for those who can afford it.
I’ve never seen anybody wear runway fashions, including people as thin as runway models. In so far as there are changes in the styles of clothing that nearly anybody wears, they happen very slowly and don’t appear to be following the runway fashions. Indeed, I suspect any influence goes the other way. Every once in a while some fashion designer will copy some street fashion.
The same thing appears to me to be happening with fashions in body style. It was claimed that there was a trend for “heroin chic” in women in the 1990’s, while today there is a trend for women being pumped up. I don’t see any evidence that such a thing has actually happened anywhere except in the minds of the several dozen fashion czars who control what image of women is shown on fashion runways, women’s magazines, TV shows, movies, etc. In so far as there is any real change in what most people’s bodies look like, the statistics say there has been a trend among American men and women for putting on weight (and not muscle) over the past twenty years.
I think the assumption that the ornaments correlate wth increased risk is not a given. Clearly, if having grand tails were a significant risk, selection pressures would drive the trait to more modest proportions. Some researchers have found that the elongated tails even aid in protecting peacocks, as inexperienced predators will often leap upon the tail, rather than the body of the bird, giving it a chance to escape. My point here is that assumptions about preceived negative risk, or squandering of resources, or however one might wish to phrase it is based more on human perceptions about what “should” be than what really is. The simplest explanation is that the peacock’s tail is of sufficiently large size to act as an advertisement for health and vigor (i.e., for “good genes”), and not as burdensome as human sensibilities might expect. The tail did not evolve in isolation as a sexual display, at the cost of anything.
This can only work if the ruse is successful, in which case the individuals fooling their prospective mates with their false ornaments will still be found out in subsequent generations. If the specimen is truly not up to par, then even if he does manage to attract a mate over his more “fit” rivals, his offspring will suffer for it.
Note, however, that the key to natural selection is that on average, such individuals will ultimately not be successful. It matters not if one, or even a few, individuals manage to fool their mates with grand displays which, in their cases, do not accurately signify their true genetic stature (so to speak). Those who are the real deal will still get the goods more often (especially since there is very often more to successful mating than mere display; you have to be able to walk the walk, not just talk the talk, when rivals come a-courtin’).
It’s not a matter of motivation, it’s simply a matter of differential survival among species, rather than individuals. Mass extinctions, for example, are an obvious instance of such differential survival - some species weather the environmental changes, some die off.
