Population benefits of sexual selection confirm that males are useful

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Biologists have long puzzled about how evolutionary selection, known for its ruthless requirement for efficiency, allows the existence of males — when in so many species their only contribution to reproduction are spermatozoa.

But research published…in Nature shows that sexual selection — when males compete and females choose over reproduction — improves population health and protects against extinction, even in the face of genetic stress from high levels of inbreeding.

The findings help explain why sex persists as a dominant mechanism for reproducing offspring.

Lead researcher Prof Matt Gage, from UEA’s School of Biological Sciences, said: “Sexual selection was Darwin’s second great idea, explaining the evolution of a fascinating array of sights, sounds and smells that help in the struggle to reproduce — sometimes at the expense of survival.

“Sexual selection operates when males compete for reproduction and females choose, and the existence of two different sexes encourages these processes. It ultimately dictates who gets to reproduce their genes into the next generation — so it’s a widespread and very powerful evolutionary force.

“Almost all multicellular species on earth reproduce using sex, but its existence isn’t easy to explain because sex carries big burdens, the most obvious of which is that only half of your offspring — daughters — will actually produce offspring. Why should any species waste all that effort on sons?

“We wanted to understand how Darwinian selection can allow this widespread and seemingly wasteful reproductive system to persist, when a system where all individuals produce offspring without sex — as in all-female asexual populations — would be a far more effective route to reproduce greater numbers of offspring.

“Our research shows that competition among males for reproduction provides a really important benefit, because it improves the genetic health of populations. Sexual selection achieves this by acting as a filter to remove harmful genetic mutations, helping populations to flourish and avoid extinction in the long-term.”

Phew! Had me worried for a while. 🙂

RTFA for details of the analysis.

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