Youth and attractiveness in the female are proxies for fertility potential: a symmetrically shaped face, clear skin, shiny hair, slim waist, and full hips and breasts are indicators of good health and fertility potential, indicating as they do that the woman is free of parasite infection and has not given birth before (pregnancies tend to increase the female waistline), that she gives reasonable attention to personal cleanliness, and that she has enjoyed good nutrition.
I believe I have thought of an iron-clad objection to these paeans to nubile fertility, as follows:
There's more to genetic propagation that just knocking some girl up. To wit: the bun has got to get out of the oven. When I was eight months pregnant I started reading the Science Times section with extra avidity in the hopes that they might invent and perfect Star Trek-style transporter technology in the next few weeks, sparing me the awful inevitability of a live human emerging from my nether regions (can I say p****** on this blog? [No. This is a family blog. - ed.. It turned out OK in the end, thanks to my having liquid Demerol injected into my spinal column. But what about on the veldt?
One of the salient differences between humans and our proto-human ancestors is head size: we've got great big noggins what can barely fit through our narrow pelvises. "Brain size tripled in our ancestors between two and a half million years ago and a hundred thousand years ago." We've gone as far as we can in this direction while still being able to get the babies out (even though they are born comparatively prematurely and with flexible heads). So much so, in fact, that often there is a lack of fit between baby's head and mom's pelvis and both die. Many other things can go wrong on the way to live birth: having a womb shaped in such a way that the baby presents breech, persistent miscarriages, and so on.
The first birth is the most dangerous, because if there is some real structural problem, it will show up at this point. Second labors are shorter and less likely to kill mother or child. Women who have borne many children (like ten) are at higher risk again.
I think you see where I am going with this. I think that the most attractive female, from this appropriately reconsidered Darwinian perspective, should be one who bears unmistakeable signs of having given birth. That is, stretch marks, a slight out-pouching of the formerly flat stomach due to weakening of the abdominal walls, and lower, post-breastfeeding breasts ought to be the apex of sexy (provided they are combined with the other indicators of health and fertility). So, clear skin, even teeth; I'll give you that. Shiny hair? I have some concerns about this since I think our African ancestors' hair probably tended towards the kinky rather than the Bardot-esque, Clan of the Cave Bear mane these researchers seem to be envisioning. Whatever. Favorable hip to waist ratio? Again, fine. Women's waists tend to thicken slightly after childbirth even if no weight is gained, but this is probably offset by slightly wider hips as well, so they still look as fertile as before.
I'm not denying that men would be attracted to fertile women. Sperm is cheap [I'll say. -ed..] The appropriate male evolutionary strategy is obviously to have sex with as many women as will let you (and perhaps some who won't). I'm just saying that, confronted with two women of equal attractiveness and the same age, one of whom has all the favorable features listed above but has obviously never given birth, while the other obviously has given birth, the latter ought to be the most attractive.
Absence of the baby or child is no evidence of genetic unfitness, since accidents will happen. But presence of a healthy child constitutes abundant evidence that the woman is fertile, has given birth to normal young without dying, can breastfeed sucessfully, and exercises optimal care of any children she has. If the baby is too young, she is likely not ovulating yet. So, the sexiest woman in the world ought to be the stretch-marked hottie above with a healthy, bright-eyed little person toddling around after her. And yet, I submit that this is not generally regarded as a description of the world's sexiest woman (except by my husband who has various vested interests). So perhaps, just maybe, there is a little more to current beauty norms than some potted ad hominid arguments would suggest.