[bermanoid]

Secondly, the author doesn't make a convincing argument that the fact that the reason why men get all the risk and all the reward is because of something innate, instead of a self-perpetuating social system that actively encourages one gender to risk it all and reap the rewards, while holding back the other gender to mediocrity and risk-free existences.

The author may not have gone into it, but the argument exists, based on what we know about genetics and reproduction.

Female reproduction is inherently limited, first of all by the time it takes to have a single child, second by the probability of death due to childbirth (relatively small, but not insignificant for most of human history), and third by the reduced fertility that comes with age.

Male reproduction is essentially unlimited; the potential maximum "genetic fitness" (measured by simple count of the branches you spawn on the tree of life) of becoming a king and impregnating an entire harem of women over your life is easily 10x the maximum "fitness" for a woman (though the probability is very low for such extreme situations), so it's to be expected that any preferentially male-expressed genes that would increase the probability of ending up in that situation would be more prevalent in the gene pool than the corresponding traits for women (which would be mostly neutral evolutionarily, since a woman with a male harem is not going to spread, on average, more copies of her genes than she would in normal life).

We don't need to assume that the dominant factor is the king + harem situation, either; it's enough merely that men, on average, see wider variability in reproduction than women do (cheating, cuckolding, etc. tend to make that happen).

The "leaps of faith" required to let this explain increased male risk-seeking are:

a) That the traits we associate with risk seeking correlate well with the traits that cause men to be highly genetically successful

b) That the way things actually transpired in history, the variance in male genetic success was, in fact, significantly higher than the variance in female genetic success. Note that we are not talking about averages (they're equal, quite trivially), but variances

If you accept a) (which is not much of a stretch - sleeping with other men's wives is definitely a risk-seeking behavior that increases genetic success for men), then it's absolutely 100% certain that the amount of genetically linked risk-seeking will be higher (or equal) in men than in women. It's very easy to make a similar argument that implies that any genetically linked risk-avoidance genes that are preferentially expressed in females will be more common than those that are expressed in males, at least to the extent that they would reduce male reproductive variance without a corresponding survival benefit.

Bear in mind that your comment about a "self-perpetuating social system" and the things that it encourages may not be entirely off-base, but that doesn't change the genetic imperatives: given what we've seen above, such a social system would align very well with the genetic best interests of its constituents, so it's hardly a stretch to imagine that the two factors have coexisted and reinforced each other quite strongly.

[geebee]

Female reproduction isn't as limited as it might seem at first glance, because you need to consider the reproductive success of her offspring as well. If we're going to see life as DNAs way of making more DNA, Genghis Khan's mother did just as much reproducing as his father.

I've read that female bonobos, for instance, take a great interest in the mating success of their male offspring:

"http://www.indstate.edu/news/news.php?newsid=1742

So having a high social status in the pecking order can absolutely translate in to "unlimited" reproductive potential for a female in this case.

An interesting quote:

"Scientists believe a bonobo mother's rank in the group has an impact on her son's reproductive rank because if she dies the son falls in rank and becomes unimportant."

[bermanoid]

If we're going to see life as DNAs way of making more DNA, Genghis Khan's mother did just as much reproducing as his father.

I absolutely agree with you about that, and in fact, the genes that made Genghis Khan reproduce so wildly may have even come from his mother. They may not have been linked to sex at all, and might be expressed equally in his male and female descendants.

None of which changes the conclusion, though, which is that if there are any sex-linkages (either by presence on the Y chromosome or by preferential expression) amongst the genes controlling risk (reproductive risk, especially), then they will tend to accumulate in such a way that the high risk male genes are much more strongly selected for than female ones (which will be mostly neutral if they're not deleterious).

Put another way, the "risk-seeking" phenotype is not the same as the "encourage male offspring to be risk-seeking" phenotype, and while the former is only beneficial to male genes, the latter is beneficial to everyone's. And the end result is that male risk seeking is encouraged in the gene pool in many ways - in fact, what you've suggested is that the social reasons that male risk-seeking is encouraged are actually quite strongly selected for individually, which puts the conclusion on even stronger genetic grounds (as opposed to what comes up often as the more PC theory, that it's just an accident of history that society decided to bring up males that way, not an evolutionary imperative).

The stuff about bonobos is quite interesting, I hadn't seen that before. They have a quite different power structure that makes things very unusual (almost inverted, in many ways), and it's very interesting to see that increased reproductive variance there is not linked to dominance, but to keeping a good position within the female hierarchy. It makes very clear the point that while a lot of (human) male traits may be evolved in order to increase reproductive variance, those traits do not necessarily achieve that goal (or any positive goal) in general, but only within the context of our other evolutionary peculiarities. As usual, it's difficult to evaluate anything in a vacuum.

[seigenblues]

First, i agree with basically all of your logic & reasoning as you've laid out. However, you lost me at the conclusion:

  If you accept a) (which is not much of a stretch - sleeping with other men's wives 
  is definitely a risk-seeking behavior that increases genetic success for men)

The reverse is true as well: sleeping with people not your husband is a risk-seeking behavior that also increases genetic success for women. But the way you've phrased it is so loaded in "the way things are" that it's hard to see just how prevalent the cultural norms are ingrained.

For instance, imagine a world where it's all switched around: women are assumed to be the risk-taking, sexually aggressive gender, and society is organized in a pretty clear matriarchy, women make 30% more than men, etc. A woman who sleeps with another woman's husband, while certainly "more obvious" ("how is she pregnant, again!") could be just as 'culturally accepted' as men sleeping with other men's wives are here. There are certainly examples in the animal kingdom -- female dominant, where females maximize their genetic 'success' by successfully having children of many males. "female dominant animals" is a very rich google vein ;)

So a better question to ask is "why did that not happen with homo sapiens sapiens?"

Please note also the huge amount of cultural assumptions about behaviors, norms, & risks, in the tiny sentence fragment "sleeping with other men's wives". Which implied pronouns are the active ones there, which are the passive objects acted upon, etc.

[bermanoid]

sleeping with people not your husband is a risk-seeking behavior that also increases genetic success for women. But the way you've phrased it is so loaded in "the way things are" that it's hard to see just how prevalent the cultural norms are ingrained.

Sleeping with more than one man may decrease a woman's time-spent-not-pregnant by a small factor. But no matter how many women a man is already sleeping with, adding one more will always increase his reproductive success by the same amount. The potential gain due to "cheating" is much higher for a man's genes than for a woman's because he has no downtime.

That has nothing to do with cultural norms, it's just biology.

There are certainly examples in the animal kingdom -- female dominant, where females maximize their genetic 'success' by successfully having children of many males.

Yes, the inverted world scenario could have happened with humans, as it has in a few cases (lemurs, bonobos, and hyenas).

But I think you're misinterpreting why it comes about in those cases. There is no suggestion that it emerges because it in any way increases the probability of a woman getting pregnant; to the contrary, that's the easy part, most researchers think female dominance is more related to ensuring that adequate resources are available to ensure the survival of the mother and offspring, which is a different issue altogether.

In those types of societies, we should (and do!) find that male reproductive risk seeking is more muted, because such risk seeking no longer carries with it significant evolutionary benefit - with females in control of the hierarchy and (limited) resources, and quickly impregnated when they're able, a male maximizes his potential success by staying alive, playing nice, and working to make sure the children survive. There's no contradiction there with what I've suggested: if you change the environmental constraints (social, developmental, and physical), the optimal evolutionary responses to those constraints change, too.

Such a society would be quite different in many ways, and the evolved differences between the sexes would be much smaller (lemurs display very minor sex differences compared to most mammals). But we should not pretend that the very real evolutionary pressures humans evolved in response to are not there just because things worked out the opposite way for a tiny fraction of mammals, and in the absence of a female dominant social structure, male risk seeking tends to have a significant evolutionary payoff. When we see evidence of it in humans, I don't see anything wrong with recognizing the incentives that lead to its expression.

So a better question to ask is "why did that not happen with homo sapiens sapiens?"

To put it bluntly, we can ask the question, but it's trivial to answer: female dominance is such an aberration in the mammalian world that it's probably selected against. 3 known examples out of more than 5000 species is under .1%, small enough that we can assume that in the evolutionary space and ecological habitats that we exist, female dominance has not been an optimal reproductive strategy. Even if it was neutral, we should be seeing more instances due to drift.

That's not a moral value judgment, or a justification, or anything like that - we're not slaves to our genes, we have the ability to overcome our instincts and emotions, and we should do so whenever they lead us astray. I think most reasonable people these days agree that dominance in any form is a primitive trait whose expression we should be trying to eradicate from our society.

But the current trend in some circles is to claim that in humans, most sex differences are purely social constructs, and hence are not influenced in any meaningful way by our genes or evolution. Which is bollocks - genetics and society are highly intertwined in most species, performing a delicate coevolutionary dance where one can't move without the other compensating accordingly, and this is something that any evolutionary biologist sees every day. Like nature vs. nurture, socialization vs. genetics is an argument for the fools, they happen together, and it's supremely naive to argue for one to the exclusion of the other.