High testosterone may mean shorter lives

A North Dakota State University study suggests males with higher levels of testosterone sire more children, but have shorter life spans.

Wendy Reed and colleagues followed a group of dark-eyed juncos, small mountain songbirds found across North America, through seven breeding seasons. The scientists injected males with elevated levels of testosterone and found they had shorter lives, but sired more offspring -- even with females who were mated with other males.

"The surprising result was that testosterone-treated males had a higher overall fitness than control males," write the authors in the May issue of American Naturalist.

"Although testosterone increased male fitness, as measured by lifespan and number of offspring, the extended effects on offspring and female mates were generally negative and may ultimately constrain the evolution of higher testosterone levels in males," said the authors.

Copyright 2006 by United Press International