Peacocks might not shake those tail feathers for the reasons you think

February 2, 2016
A provocative study by evolutionary biologists at McMaster University takes on one of Charles Darwin’s central ideas: that males adapt and compete for the attention of females because it is the females who ultimately choose their mates and the time of mating. Credit: Wikipedia/Jebulon

What if Darwin was wrong?

A provocative study by evolutionary biologists at McMaster University takes on one of Charles Darwin's central ideas: that adapt and compete for the attention of because it is the females who ultimately choose their mates and the time of mating.

Instead, new research using fruit flies as a representative species indicates that females do not have specific preferences, suggesting that 150 years of evolutionary theory around mating choice may need to be tossed out.

"Darwin's female-choice theory has become the foundation for explaining the presence of exaggerated secondary sexual traits in many males, such as the peacock's tail feathers," says evolutionary biologist Rama Singh, an author of a paper in the journal PLOS One that explains the findings.

"It has also led to a cottage industry based on the idea that female choice is based on the genetic quality of the males, known as the 'good gene hypothesis'," Singh says. "Sexually exaggerated traits are said to be male advertisements to females of their good genes, when in fact they may simply be a means of making the male more visible to females or intimidating other males."

Did Darwin get it right? Could it be that the Victorian values of his time, when men tipped their hats and made other exaggerated displays of sensitivity to women, subtly affected Darwin's scientific thinking, leading him to attribute a veto power to females in matters of sexual negotiations? Is female choice more apparent than real?

When a female seems to "choose" a large male over a small male, how do we know if she really prefers the large male or she is making the "choice" under coercion or threat, or if the large male has eliminated others from the competition?

Singh and his co-authors designed a simple trick to answer these questions. Using a garden variety of fruit fly, Drosophila, they sexually aroused a female with a male (large or small), then removed the male and offered the female two fresh males – one small and one large. The results were clear-cut and unambiguous: the aroused females did not show any particular preference for large males and mated as if randomly, leading the authors to conclude that once sexually aroused, females have no preference in terms of mates.

The key to understanding the question of choice may be in the longer time it takes female fruit flies reach a state of arousal – a lag that is often misinterpreted as females exercising mate choice.

In matters of and mating, there is no such thing as pure male charm, Singh says. All male moves can be seen as tinged with direct or indirect coercion or threat of physical force.

This may be so because the physical strength and aggressive behaviors that males develop through male-male competition can also be used in male-female sexual interactions, which are all lumped into "male sex drive" a term proposed by Singh as a complement to Darwin's "".

In the case of humans, Singh says, things are different. Sexual behaviors are not hard wired; we assume that they can be modulated and moderated through rules of social interactions imposed by the brain's veto power over the body.

Explore further: Female mice do not avoid mating with unhealthy males

Related Stories

Female mice do not avoid mating with unhealthy males

March 13, 2015

Female mice are attracted more strongly to the odour of healthy males than unhealthy males. This had already been shown in an earlier study by researchers from the Konrad Lorenz Institute of Ethology at the Vetmeduni Vienna. ...

Male squid unfazed by costly sex

January 15, 2016

Sex is costly. It can be time consuming, energetically demanding, and resource depleting. So, it makes sense to choose your mates wisely.

Recommended for you

Finding a lethal parasite's vulnerabilities

December 15, 2017

An estimated 100 million people around the world are infected with Strongyloides stercoralis, a parasitic nematode, yet it's likely that many don't know it. The infection can persist for years, usually only causing mild symptoms. ...

Loose skin and 'slack volume' protect Hagfish from shark bites

December 14, 2017

Chapman University has published new research showing how hagfishes survive an initial attack from predators before they release large volumes of slime to defend themselves. Because the slime is released after they are attacked, ...


Adjust slider to filter visible comments by rank

Display comments: newest first

3 / 5 (2) Feb 02, 2016
So hundreds of research studies on vertebrates are wrong because one upon the peculiarities of how female flies get aroused after a brief encounter with two male flies of different sizes? Darwin's theory might be wrong and reflect attitudes of the Victorian period but this work is irrelevant to whether that is or is not the case.
not rated yet Feb 03, 2016
There's another theory - the feathers are used to deter predators. If eyes are considered repulsive and "dangerous" to predators (butterflies, blue-ringed octopus), why not peacock feathers? Nearly every study has been done on captive birds with the assumption peacocks are polygamous. With predator pressures in the wild, this may not be the case. Yes, sexual selection is still involved (because females may choose healthier dominant males).

Consider that these animals have been in an evolutionary arms race with reptiles (snakes and lizards). Indeed, the sound created by shaking their quills may mimic snake hissing.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.