'Women living in stressful times give birth to more girls than boys. '
When times are tough -- during drought or famine, for instance, or even during a more modern-style calamity such as massive layoffs from a large company -- stress hormones in a woman's body have an influence on the sex of her child or children, should she have them at this time: Thanks to evolution, there's a slightly higher chance she'll have a girl, since daughters stand a better chance to reproduce during hard times than men do. Recently, UC Berkeley researchers discovered that stress hormones make the uterus slightly more hostile to a male fetus during tough times, and further, that the body will spontaneously abort more boys than girls.