Sons and Mothers

A really interesting study from Finland, discussed in the October issue of Scientific American, shows that:

• sons reduce a mother's life span by an average of 34 weeks.
• girls from mix-gender twin pairs are 25% less likely to have children, had at least two fewer children, and were about 15% less likely to marry than those born with a sister.
• mothers of opposite-sex twins end up with 19% fewer grandchildren than moms of same-sex twins.
• 100 to 150 years ago, 40% of babies died before they reached adulthood.