Scent of Family Guides Girls' Maturation

Hundreds of millions of years of evolution have given us one great reproductive insight: Incest is icky.

Inbreeding is the king of evolutionary no-no's. Related parents are more likely to have similar genetic mutations, so children of incest are at a high risk for birth defects and disease.

A natural aversion to incest is not the only mechanism that may have evolved to prevent inbreeding. A new paper published in the American Journal of Human Biology concludes that having a male in a household can affect the timing of menarche, when a young woman first gets her period.

The Pennsylvania State University team who performed the study attributes the effect to pheromones that evolved to thwart inbreeding. Yes: In a sense, the constant smell of dad is enough to stall puberty.