Interestingly some researchers believe that sex is determined due to hormones (rather than genes - i.e. it's not possible to create a breed that biases one sex more than another), and that there is a bias in animal (including human) populations. It's not determined by a simple roll of the dice.
In some insects the female is able to select gender specifically by fertilising the egg with sperm or withholding it.
In others, it seems that it has to do with ambient temperature, abundance of food, etc. If there are enough resources to make a large offspring, the most optimal one is produced that can benefit by being largest. In turtles it's a female, in crocodiles a male is produced (IIRC).
Anyway, in humans, higher rankers typically have male offspring. Apparently American presidents have had a disproportionately large number of sons. Poorer families typically desire - and apparently some studies indicate produce - more girls. This can again be explained by what is most optimal. It's more common in human societies for males to inherit rank, whereas women can marry into it. So poorer families in some cultures bequeath more wealth to women for dowries so they can try to buy their way into higher classes. By contrast, higher ranking men can father more children.
I'm basically regurgitating what I've been reading in The Red Queen. Not my ideas - check out the book. It's very interesting.
Sample sizes have nothing to do with it. If you want to study the determinants of presidency in the US it's a 1:1 sample.
I keep repeating this on news.ycombinator: statistical analysis is predicated on the prior hypothesis that the stuff you're measuring is orthogonal to the stuff that you can't measure.
So: what are we measuring? What are we _not_ measuring? Is our theory that people exerting power have more testosterone and hence have more sons? That can be tested in wider populations, and including presidents might just be a huge confounding factors. Is it that presidents become powerful because they have the Mystery Factor, and that, too, is behind the excess sons?
If, by construction, only presidents have the Mystery Factor, we have to start from there. But then we need theories about the Mystery Factor to test. And controls, men who haven't become president by a matter of chance, and so on.
On the other hand: you can have huge datasets generated from website design tests and still end up doing "A/A testing" and such cargo cult statistics, complete with sacrifices to the gods of large sample sizes.
In some insects the female is able to select gender specifically by fertilising the egg with sperm or withholding it.
In others, it seems that it has to do with ambient temperature, abundance of food, etc. If there are enough resources to make a large offspring, the most optimal one is produced that can benefit by being largest. In turtles it's a female, in crocodiles a male is produced (IIRC).
Anyway, in humans, higher rankers typically have male offspring. Apparently American presidents have had a disproportionately large number of sons. Poorer families typically desire - and apparently some studies indicate produce - more girls. This can again be explained by what is most optimal. It's more common in human societies for males to inherit rank, whereas women can marry into it. So poorer families in some cultures bequeath more wealth to women for dowries so they can try to buy their way into higher classes. By contrast, higher ranking men can father more children.
I'm basically regurgitating what I've been reading in The Red Queen. Not my ideas - check out the book. It's very interesting.