Female ducks can thank evolution for avoiding becoming impregnated by undesirable but aggressive males endowed with large corkscrew-shaped penises: vaginas with clockwise spirals that thwart oppositely spiraled males. That's right, males are literally screwed.
The research on this evolutionary 'battle of the sexes' at the genitalia level were described in the December 23 issue of the journal Proceedings of the Royal Society B.
"In species where forced copulation is common, males have evolved longer penises, but females have coevolved convoluted vaginas with dead-end cul-de-sacs and spirals in the opposite direction of the male penis," said Patricia L.R. Brennan, lead author of the paper and postdoctoral researcher in the Yale Department of Ecology and Evolutionary Biology. "This coevolution results from conflict between the sexes over who is going to control fertilization."
The research builds upon a 2007 Yale study that first described the strange morphology of a duck's sexual organs. While most birds have no phalluses, ducks turn out to have relatively large, flexible penises—up to 20 centimeters—tucked inside their bodies. During sex, male ducks extend, or evert, their phalluses inside the female. Brennan and her Yale colleagues used high-speed video to document the erection of the duck penis for the first time and found the whole process takes less than half a second—an act the Yale team described as "explosive."
Such large phalluses are supposed to give males a reproductive advantage when there is much forced mating. However, the Yale team hypothesized that females could make copulation difficult for the males with their complex genitalia. And, they wondered, do the convoluted vaginas of some waterfowl help those females exclude forced copulation?
To test the hypothesis, Brennan and colleagues examined duck penis eversion in a set of glass tubes with different shapes. A straight tube or a tube that spirals in the same counter-clockwise direction as the male penis doesn't slow down the eversion process. But glass tubes that mimic the female vaginal shapes with a clockwise spiral or a sharp bend can completely stop the penis from everting. These results suggest females have evolved anatomical mechanisms to impede forced copulation, and provide new insights into the evolutionary consequences of sexual conflict over reproduction, say the scientists.
The anatomical evolutionary race to control reproduction is one of the more dramatic examples of sexual conflict in nature.
"Although we predict that sexual conflict should be ubiquitous, finding a system where the 'arms race' between the sexes is so dramatic is exceedingly rare. Ducks are providing us with an incredible opportunity to understand the evolutionary consequences of conflict," said Brennan.
Other authors on the paper are Christopher J. Clark and Richard O. Prum, both from Yale. The study was funded by Yale University.
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Why An Extra Planet Can't Be Hidden Behind The Sun Or Above The South Pole
- My Applied National Security Paper. Being President Isn't For Idiots.
- Why Has Organic Farming Flatlined?
- Hugh Hefner's Wife Was Not Poisoned By Breast Implants
- Top Scientists Chastise Greenpeace
- SYRINA: A Trojan Horse For Endocrine Disrupting Chemicals?
- The Daily Physics Problem - 5
- "So what was the precipitating event which caused your re-evaluation?..."
- "I try this one... I am a bit rusty, so my solution can be dramatically wrong. Given that B is uniform..."
- "wow! with a name like Wilhelmina Pelegrina, she can't do no wrong. also,some of the problems in..."
- "This is the best you could do? Golden Rice is in the public domain - the lack of any corporate..."
- "Dylan, okay first TL:DR, the answer is that for anything of 10 km upwards, months or a year or..."
- Happy World Hepatitis Day!
- Ovarian Cancer – Redux
- New York Is Second In Health Care Premiums, Last In Hospital Quality
- USPSTF Advisory on Skin Cancer Screening Provokes Concerns from Docs
- Cancer As Modern Lifestyle Disease? Only If There Was Processed Food 2 Million Years Ago
- Blood Test for Alzheimer’s: Close Or Hype?