Humans, animals delay reproduction during food scarcity

July 2nd, 2009 - 3:39 pm ICT by IANS  

Washington, July 2 (IANS) Humans and animals delay reproduction during food scarcity, so that they may live longer to boost chances of reproduction later, says a new study.
The discovery by University of Minnesota (U-M) researchers, which explains why starvation can lead to longer life, has important implications for improving human health and lengthening lifespan.

Conversely, if bad times turn to good times and the population is on the verge of a boom, reproducing sooner rather than later will help their genes thrive.

“If the population is decreasing, future kids make a bigger splash in the gene pool than current kids,” explained Will Ratcliff, a U-M College of Biological Sciences (CBS) student who came up with the idea for the study.

“So, if there are tradeoffs between current and future reproduction, delaying reproduction can be a good idea, even if it reduces the number of kids you have during your lifetime.”

Fluctuations in testosterone levels provide an example of how the environment and organisms interact to guide reproduction, explained R. Ford Denison, professor at CBS.

Testosterone suppresses the immune system. So when environmental conditions trigger high levels, reproduction is high but longevity drops.

Environmental factors also control the age of puberty.

In African countries with chronic food shortages, girls experience puberty much later than in the U.S., where rich diets trigger early puberty, said a U-M release.

Food scarcity is a signal that the population is likely to decline, so reproduction is delayed, while an abundance of rich food signals an increase, causing reproductive age to drop.

“Our hypothesis may explain hormesis, the mysterious health benefits of low doses of toxins - including those that plants like broccoli make to defend themselves from insects,” said Denison.

These findings were published in the June 25 issue of PLoS One.

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