My main interest is the study of copulatory traits and the selective forces that shape their
morphology and function.
In particular I look at vertebrate genitalia, specially female genitalia and its coevolution with male genitalia. I am also and advocate for science education and science funding particularly in the field of organismal biology.
Genitalia are often the battleground of warfare between the sexes, and they are wildly diverse structures!
Female mallards have twisted vaginas that make intromission by unwanted males difficult. The male penis spirals in a counterclockwise direction while the female spirals in a clockwise direction
MY RESEARCH HAS BEEN FEATURED IN several BOOKS
Zimmer, C. (2010). The tangled bank. An Introduction to Evolution.
Long, J. (2011). Hung like an Argentine duck: a journey back in time to the origins of sexual intimacy. HarperCollins Australia.
Zimmer, C., & Emlen, D. J. (2013). Evolution: making sense of life. Macmillan Higher Education.
Schilthuizen, M. (2014). Nature’s nether regions. Viking, New York.
Gray, P. B., & Garcia, J. R. (2013). Evolution and human sexual behavior.
Birkhead, T., Wimpenny, J., & Montgomerie, B. (2014). Ten thousand birds: ornithology since Darwin. Princeton University Press.
Bondar, C. (2016). Wild Sex: The Science Behind Mating in the Animal Kingdom. Pegasus Books
Prum, R. O. (2017). The Evolution of Beauty: How Darwin's Forgotten Theory of Mate Choice Shapes the Animal World-and Us. Doubleday. One of 2017’s NYT Best books.
Willingham, E. (2019). Phallacy: Life lessons from the animal penis. Features my research in one chapter after extensive interviews and one in person lab visit
Cooke, L. (2022). Bitch. Females in nature. Features my research in one chapter after extensive interviews and one in person lab visit.
Gross, R. (2022). Vagina obscura. Features one chapter on my research after several in depth interviews and one in person lab visit.
Dever, J. (2023). Female Biology. https://pressbooks.pub/femalebio/ . An online textbook.
Hall, S. (2025) Slither. How nature’s most maligned creatures illuminate our world.
York, Carly Ann (2025). The Salmon Cannon and the Levitating Frog: And Other Serious Discoveries of Silly Science.
Poole, Megan (2025). Listening to Beauty. Rhetorics of Science in Sea and Sound.
WHY SO MUCH INTEREST? Genital evolution is amazing!
Genitalia are some of the most diverse structures in nature, and this diversity goes beyond what is needed for simple transfer of male gametes into the female. Because genitalia are structures that interact directly during copulation, coevolution between males and females is likely. Male genitalia can evolve through selection for males to either seduce females, outcompete rival males who also copulate with the female, or to directly counteract female interests bypassing her choice or directly harming her to increase male success. Females of course evolve genital features that allow them to prevent such male imposed costs. I have discovered that ducks are a great example of this arms race, and this discovery has had an important effect on understanding the role of sexual conflict in evolution. Males have evolved explosive penis eversion that allows them to inseminate females quickly despite their resistance, females have evolved convoluted genitalia that prevent males from everting their whole penis in the female oviduct, and species with different levels of male coercion have different genital morphology: from simple genitalia when no coercion takes place, to very convoluted when coercion is common. In other groups, females can evolve to detect subtle differences between males, and to manage sperm from preferred males. In my lab we study vertebrates: Ducks, Bats (in collaboration with Dr. Teri Orr, a prior postdoctoral fellow in my lab), dolphins (in collaboration with Dr. Dara Orbach), and more recently sharks and alpacas. My latest project is on the evolution of snake genitalia, thanks to an NSF grant. We are developing methods to study male and female morphology in 3D. My previous post-doc Dr. Rachel Keeffe, and I are still collecting and analyzing data!
Great tinamou may not be very attractive, but their breeding biology is fascinating.
Tinamou mating system and egg color
Tinamous are poorly studied neotropical birds with exclusive male parental care. They are close relative to ostriches and other flightless birds. They lay incredibly colorful eggs that are somewhat paradoxical given that they are laid directly on the ground. I found that despite the presence of exclusive male care and very high incubation constancy, great tinamou males take care of up to 30% of chicks that they did not sire. This is likely the result of high predation pressure that increases the demand for eggs. Females are always moving between males and they can easily carry sperm from previous matings. Rather than waiting for sperm from previous matings to become unviable, a process that could take many days, male tinamous simply mate with the females and take her eggs quickly to complete a clutch. The female then moves on and lays eggs. We also discovered that the visual system of tinamous allows them to see ultraviolet spectrum.
The eggs of the Great Tinamou are a beautiful turquoise color that sharply contrast the brown leaves where they are laid
Defending basic science
In 2013, my research was attacked by extreme right wing media after a story was published about how I got federal funding to study duck penises. I have since started a campaign to support scientists who are similarly attacked, and to educate other scientists about how we can act to prevent these unfounded political attacks from being a viable strategy in the first place. I wrote an op-ed in Slate, and have written 2 papers about the importance of basic science defense.