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War has rarely had a significant effect on populations, certainly nothing like the effect of disease. Although many men in the ancient world died by violence (a

War has rarely had a significant effect on populations, certainly nothing like the effect of disease. Although many men in the ancient world died by violence (as they do in pre-political societies and failed states today) killing with stone tools is pretty difficult and dangerous, so constant warfare that killed enough men to account for a 17:1 reproductive ratio for long enough to leave its mark today would have made agriculture almost impossible. So it isn't all that likely. Social constraints on reproduction are considerably more likely. All human societies are mildly polygynous, with high-status males having more mates and low-status males having fewer. This is why human males are somewhat bigger than human females: bigger men were more successful in mate competition, despite the obvious disadvantage of a larger size for a tool-using opportunistic hunter-gatherer-scavenger []. The remarkable thing about this finding is that the level of social control was high enough to sustain such an effective* exclusion of most men from mating opportunities. In every modern human society cheating ("extra-pair copulations") is a significant factor in reproductive statistics, and a 17:1 ratio suggests a system that was capable of actually excluding, not just nominally excluding, the vast majority of men from reproducing. It's difficult to see how that could happen in a modern human population, but then again: men and women today are descendents of the 5% of males who were successful in reproducing under those circumstances, so it's not entirely implausible that we are considerably fiercer mate competitors than our pre-agrarian ancestors. [*] Bigger, more muscular bodies require more fuel, so bigger men starve to death more frequently than smaller men during bad years, which all the data we have on pre-political peoples suggest were not infrequent.

dragonwriter 12y ago
> and a 17:1 ratio suggests a system that was capable of actually excluding, not just nominally excluding, the vast majority of men from reproducing. It doesn't actually imply that, because many of them could have reproduced, but not had offspring that survived to reproduce for sufficient numbers of generations. Modern DNA won't distinguish that from didn't reproduce. So, the fact that the vast majority of men of the time weren't successful in reproducing in the long term (viewed by having descendants survive to the modern day) doesn't mean that they were effectively excluded from reproduction.
- tjradcliffe 12y ago
  That's a fair point. Thinking about limit-case scenarios, if the bottleneck lasted long enough, this could be a matter of 5% of the men having 1+epsilon male offspring and 95% having 1-epsilon male offspring. For even relatively modest values of epsilon that would give quite a large deviation in the population, given enough time. The article suggests this went on for about 2000 years (8000-6000 BCE) which is 100 generations, so if epsilion was 0.05 then the favoured class would have fathered 99.5% of the male population at the end of that time (most of whom would have fallen into the unfavoured class over time, of course.) Because all women reproduced (more or less) I think they just fall out of the calculation. So you are correct. [Edit: the article actually suggests it was as much as 4000 years, so an even smaller disparity could work.]
brc 12y ago
You don't have to survive long to pass on your genes. You don't need to make it past 30 to produce a big range of offspring.
deciplex 12y ago
> Bigger, more muscular bodies require more fuel, so bigger men starve to death more frequently than smaller men during bad years, which all the data we have on pre-political peoples suggest were not infrequent. Take a group of ten males. Restrict their access to food such that eventually a few of them will die. What are some characteristics that the surviving males will share? One of them is not "they are physically weaker than the dead males".

dragonwriter 12y ago

> and a 17:1 ratio suggests a system that was capable of actually excluding, not just nominally excluding, the vast majority of men from reproducing. It doesn't actually imply that, because many of them could have reproduced, but not had offspring that survived to reproduce for sufficient numbers of generations. Modern DNA won't distinguish that from didn't reproduce. So, the fact that the vast majority of men of the time weren't successful in reproducing in the long term (viewed by having descendants survive to the modern day) doesn't mean that they were effectively excluded from reproduction.

tjradcliffe 12y ago
That's a fair point. Thinking about limit-case scenarios, if the bottleneck lasted long enough, this could be a matter of 5% of the men having 1+epsilon male offspring and 95% having 1-epsilon male offspring. For even relatively modest values of epsilon that would give quite a large deviation in the population, given enough time. The article suggests this went on for about 2000 years (8000-6000 BCE) which is 100 generations, so if epsilion was 0.05 then the favoured class would have fathered 99.5% of the male population at the end of that time (most of whom would have fallen into the unfavoured class over time, of course.) Because all women reproduced (more or less) I think they just fall out of the calculation. So you are correct. [Edit: the article actually suggests it was as much as 4000 years, so an even smaller disparity could work.]

brc 12y ago

You don't have to survive long to pass on your genes. You don't need to make it past 30 to produce a big range of offspring.

deciplex 12y ago

> Bigger, more muscular bodies require more fuel, so bigger men starve to death more frequently than smaller men during bad years, which all the data we have on pre-political peoples suggest were not infrequent. Take a group of ten males. Restrict their access to food such that eventually a few of them will die. What are some characteristics that the surviving males will share? One of them is not "they are physically weaker than the dead males".