Girls might have figured out that the world can't survive without them.
Anyway, I remember seeing on some TLC / discovery thing that In nature alot of female animals will go out and get knocked up by 'good breeding stock'... and then bring the surprise home to their mate that is more prone to stick around and provide her with security.
..... I'd be interested in knowing the statistic for number fathers who think a kid is theirs that isn't.
