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Lizard Dicks Evolve Remarkably Fast

New research confirms a long-held belief that genitalia evolves more quickly than other body parts.
January 14, 2015, 9:45am
​A giant Anole lizard. Image: ​Geoff Gallice/Flickr

You may have missed this story, especially if your inbox filters out news concerning penis evolution, but there's been a recent discovery ​on that front. Researchers have found the penises on some species of lizards evolve six times faster than other body parts, according to a study pub​lishe​d in this month's Journal of Zoology.

The belief that genitalia evolve more quickly than other body parts in many animals has floated around the​ biology world for decades. This is partly due to ​the observation that some animals have species that are similar in almost every other way but differ in their genitalia. But as the paper points out, there isn't a lot of quantitative data to back up this idea.

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So Harvard researcher Julia Klaczko and her team decided to take a look at 25 Caribbean Anoli​s lizard species and compare the evolution of their junk—technically called a hemipenis—to their legs and neck flaps, called dewlaps.

The researchers found the lizard penises were evolving six times faster than their legs and dewlaps and that evolution rate was consistent across three measurements of the lizards' wangs: length, width at the bottom, and width at the top.

Some of the variations in lizard schlong shape and size. Source: ​Journal of Zoology

In the paper, Klaczko muses the difference could be explained by sexual selection. There are theories that sug​gest the female members of some species seek out mates whose genitalia naturally fits better with their own, causing the species to evolve more male species with that size and shape wiener.

But there's also evidence of a kind of genital evolutionary arms race in some species, like the Musc​ovy duck. Researchers found the ducks' genitals were quickly evolving to give each sex the upper hand, respectively. The male ducks were evolving more flexible penises in order to force mating on unwilling females. The female ducks responded by evolving more intricate, sensitive vaginas that gave them control over which partner actually managed to fertilize their eggs.

This arms race, which Klaczko and team mention in the paper, could be another possible explanation for the rapid evolution of the Anolis lizard penises, but research would need to be done on the female lizards to determine their genital evolution patterns. Although understanding the female anatomy of these species would offer great insight into why and how these schlongs are evolving so damn fast, research on female genitalia is seriou​sly lacking, and even new studies like Klaczko's focus on only the male goodies.

Now that we've got some solid evidence that penises are evolving faster than legs, at least in some species, I'd say it's high time we take a look at some vaginas and find out the other half of the story.