Boys Take Energy

摘要

A study of 18th and 19th century Finnish farmers and fishermen provides new evidence that nature finds it more costly to produce the male mammal.rnSome studies have suggested that having sons takes more out of a mother, as shown, for example, by lower birth weight in succeeding offspring. Now a multigenerational analysis by researchers at the University of Sheffield in the U.K. indicates that being next in line to a brother reduces one's reproductive success.rnEvolutionary ecologist Ian Rickard and colleagues, using data from population registers of Lutheran churches, tracked the births of children and grandchildren of 653 women born between 1709 and 1815. They found 1653 surviving children born after their mothers had produced a son. These people were significantly less likely to have offspring-62%, versus 67% for those born after a sister-the researchers report this week in the Journal of Evolution and Human Behavior.