World-renowned UT Animal Behaviorist Weighs Role of Beauty in Evolution

Mike Ryan knows a lot about how circumstances can lead to a change of perspective. Take, for example, the tiny túngara frog, which lives in the jungles of Panama. He may not seem like much, with his mottled brown skin covered in bumps and whiney song. But put this little amphibian at the center of decades of research, and it turns out he can open up a world of discovery, both for Ryan and for dozens of scientists he's helped to train over the years, with new insights into how animals become beautiful – at least to each other. These lessons may also help humans better understand how our own ideas of beauty correspond with those in the animal kingdom.

Circumstance also matter for the frog's chances of landing a mate. During mating season in the Panamanian jungle, male túngara frogs gather in mud puddles and sing beautiful songs to attract female mates. Well, the frogs think they're beautiful, especially when the females hear a male add low-pitched "chucks" to the end of their whines. The more chucks, the more the ladies like it, to a point. But if the song is too sexy, the males risk attracting the attention of carnivorous bats and becoming meals instead of mates. (And humans think online dating is rough.)

All this detail was enough to initially confound Charles Darwin. Back in the 1850s, Darwin developed the theory of sexual selection, identifying mate choice and competition for mates as the two key components, to help explain why beauty exists in the animal kingdom. This shows up from the peacock's tail to birds' songs. But Darwin struggled to explain the mechanisms of mate choice: why females choose one male over another. He understood that it was happening, but not how it was happening.

"Bright colors in fishes, songs in song birds, big manes in lions, none of this stuff is good for survivorship," said Mike Ryan, an animal behaviorist and professor of integrative biology at the University of Texas at Austin. His new book, A Taste for the Beautiful, seeks to pick up where Darwin left off. "What Darwin realized right away was that beauty kills. These traits that are involved in courtship can be neutral, but if anything, they tend to decrease survivorship. Then he came up with this idea of sexual selection."

Ryan has been studying túngara frogs – and other animals – for decades. In A Taste for the Beautiful, he describes his work and that of other scientists to explain the how of sexual selection and answer questions about why animals perceive certain traits as beautiful and others not.

The answer, he argues, lies in a combination of circumstance and the female brain.

"We often say that beauty is in the eye of the beholder, so this kind of expands on that theme and says beauty is in the brain of the beholder," Ryan said. "For humans, we often think our brain is the most important sex organ, but the brain often has other things to think about than sex. In animals, the way the brain evolves to handle multiple tasks influences, perhaps, the kind of things that appear to be beautiful to females."

Mate choice can be fickle in animals and, especially, humans, but Ryan's research points out how context comes into play. In experiments in Ryan's lab with the túngara frogs, his team of scientists found this out. When male túngara frogs are ready to mate, they gather in mud puddles and sing for several nights in a row. The females only show up on the night they are fertile. However, if they don't find a mate by the end of the night, their eggs fall into the water and will not be fertilized.

An experiment was designed to discover if the females preferred different males at the beginning and end of the night. They synthesized a mating call that was supremely unattractive because it was mixed with the mating call of a different frog species. At the beginning of the experiment, the female Tungara frogs ignored the call. But by the end of the night, with the egg-drop approaching, the females were more likely to respond.

It turns out, humans do the same thing. It's called the "closing time" phenomenon, and it was developed by James Pennebaker, a psychology professor who now also works at UT.

Back in 1979, Pennebaker asked humans to rate members of the opposite sex in a bar in Virginia on a scale of 1 to 10 at the beginning, middle and end of the night. As the night went on, the women became more attractive to the men and the women found the men more attractive, too. (Visibly drunk people were left out of the study.)

A Taste for the Beautiful is the culmination of Ryan's 30-year career and is full of these kinds of stories, but it's a book that almost didn't happen.

In October 2015, Ryan was hosting a party for his lab colleagues at his home when he fell from his three-story deck.

"I'm very lucky to be alive," he said.

He suffered a spinal cord injury and spent about six weeks in the hospital. He finished the book from his hospital bed.

"Finishing this book was important to me because I'd worked so hard on it," he said.

Ryan now uses a wheelchair to get around, but it hasn't slowed him down. He's teaching more classes than ever. His upcoming book tour will take him all over the country. He still lectures internationally, having recently returned from Toronto, and is planning a trip to Munich. Graduate students in his lab accompany him on these journeys and, he says, are a great source of support. (As thanks, he often arranges for lab tours and meetings with scientists for students who go on the road with him. His current crop of students drew straws to see who would get to go on the upcoming Munich trip.)

While field work propelled much of Ryan's career – he spent part of every year in Panama for nearly 30 years leading up to the accident – today his students have taken over a lot of the work he initiated. But not all. Ryan still has a lot of questions and a lot of curiosity. He's even planning to return to Panama this summer for the first time since his accident. While he has no immediate plans for a second book, he hasn't ruled it out.

“I only want to write another book if it's going to be as much fun as this one.”