Just reading that bit about the extinction of the X chromosone. Budgies select the sex of their chicks based on the availability of food. Where there is more food, they have females so that they can stay and produce more birds there. Where there is less food, males are born to fly off and populate other areas.
I wonder if the same is happening to humans, only more slowly due to our size. In the western world, there is an abundance of food for most people. I don't know where his studies took place, but there's every chance he only looked at the average citizen. Those of us with plenty of food may be having more females, while people who are going hungry would be more likely to have males. Those without food may never be in a position to have children, so the extra males aren't born.
I'm taking a complete stab in the dark that most of us here had few problems with food and such in their childhood. I'm curious: just for a small study here at the forums, how many males and females are in your family, including yourself and siblings but not your parents? There's one female and two males in mine.
