Musings on a commentary

Over at Treehugger, a commenter on the CBC documentary The Disappearing Male wrote:

No wonder there are so many females at high schools and universities (especially Ohio State). Not that that's a bad thing, but in order for a population to sustain itself, the sexes need to be in balance as much as possible.

I understand that this might have been a facetious comment, but to the point of "in order for a population to sustain itself, the sexes need to be in balance as much as possible" I have to say, "Ummm.... No." In order for a population to maintain itself, it has to have enough source from the limiting gamete-type. In most cases in nature, it is usually eggs that are limiting. In humans, especially, eggs are the limiting factor (roughly only one egg per woman per month). If there was only one man in a population of multiple women (lets use a ratio of 1:10 here), there is a possibility for continued population (possibility of up to 10 children per ~nine months). However, if the future ratio of males to females doesn't change, inbreeding will likely occur, since all offspring in the first generation will be 1/8 related to each other.

If there is only one female in a condition with multiple males (say 10 males to 1 female), then that population is limited in the number of possible offspring produced to one per woman per ~9 months (assuming no complications) for the entire population. Again, if the ratio of males to females doesn't change, then inbreeding will become a problem in future generations. This rate is up to 10 times slower than in the previous condition (assuming no complications in either).

In order for a population to reach, say, 30 people, in the first scenario, one would only need two additional sets of offspring, while the second would require twenty sets of offspring. The first condition provides additional sets of stability, since birth-spacing would be possible in order to reach that target population (in this case 30 people). However, the second condition would require that the female be constantly making babies, and would unlikely be able to produce enough on her own before reaching menopause. (Therefore, assuming that she only produces girls, and the girls reach sexual maturity at 15, then to reach 30 people would take a minimum of 17 years, with the first daughter having two children, and the second daughter having one child).

Now, societal mores are all that keep us from having a condition where it is "okay" for one man to have several wives. However, imagine - if you will - a condition where there is only one male in a population otherwise comprised entirely of females. One has to ask oneself if - in such a condition - would all females decide that the "normal" social more of one-man and one-woman is adequate, or would some of the population see the male as a source for fertilization? I doubt that the first alternative would be the one followed in the long run if the group feels that their situation is unalterable.

Of course, this doesn't mean that I'm proposing that this whole problem of disappearing males is not a problem. Of course it is, and the social impacts will be much greater than what I outline in my very simplistic thought model above. However, I'm only discounting Ken's statement that a balance of the sexes is what is important to sustain a population. (Again, though, I haven't looked at the implications of a 1:10 ratio with regard to future inbreeding/bottlenecking.)