Finnish Scientist: Grandma Good, Grandpa Bad

Do yourself a favor and read this extremely interesting article from Scientific American about a Finnish scientist's demographic evolution study of 200 year old birth and death records. Highlights:

• Grandma's increase the reproductive success of grandchildren because they take care of their grandchildren. Certainly seems to be true to me, as I can site innumerable real-world examples of this.
• Grandfathers, meanwhile, harm grandchildren's reproductive success, probably because old men get preferential treatment in most societies, thus distracting grandmas from their real job, coddling children. This is why there is no selection pressure for men to live as long as women.
  
• The reproductive success of female twins with male twins is less than females without male twins (including female-female twins). This is chalked up to testosterone. Incidentally, my mom has a male twin, but she also had three kids, so perhaps in this case my anecdotal evidence is not so statistically significant. Not that such things ever are.
• Raising boys takes a greater toll than raising girls. This is again chalked up to testosterone contamination, which harms the immune system, although it could equally likely be due to all those hours chasing sons around with rolling pins if you ask me.