Oh holy crap man, you *know* that they've figured out what causes it, dont you?
Myself, we have a 5 year old boy, and when he was 2 my wife and I decided we wanted a girl, like having a matched set. We ended up having *twin* girls, who are now 3 years old. And I'm done. Out. Finito.
And in response to the above post... you mean they get *more* complicated as they age? Oh lordy, someone pass me the Makers Mark...