New paper out: Remodeling Male Coercion

New paper published in Evolution! Our study uses quantitative theoretical modeling to explore a new evolutionary possibility for systems involving sexual conflict over mate choice. Rather than evolving resistance traits that directly interfere with male coercive strategies, potentially leading to a co-evolutionary arms race, we show that females may evolve additional mate preferences that “remodel” male coercive capacity in order to expand and promote their own freedom of mate choice, or sexual autonomy.

A ket aspect of this work is that it demonstrates the importance of allowing female reproductive traits and behaviors greater complexity and biological realism when we build theoretical models to guide our intuition about the evolution and diversity of mating interactions.

Read on for more:

Sexual conflict is often characterized by the evolution of female resistance that directly interfaces with the male coercive strategy. A now-famous example is duck genital biology, wherein the vaginal tract of female ducks (shown on the left) is a convoluted anti-corkscrew, co-evolved with the male morphology (here on the right), seemingly allowing females to block unwanted fertilizations and retain the benefits of mating with their social partners in the face of violent coercive attempts by other males.

As you can see, these dynamics can potentially lead to a costly co-evolutionary arms-race, where the evolution of female resistance selects for more effective coercion, and so on.

In our paper, we explore a novel alternative to this arms race scenario, which we are calling “remodeling.”

Suppose females, faced with male coercion, could evolve an additional preference for a new male trait that enhances female freedom of mate choice?

Let me show you a heuristic example from nature where we think this might be going on:

This is the courtship display arena of the Tooth-billed Bowerbird (Scenopoeetes dentirostris) from Australia. A female that arrives at one of these leaf piles has never been observed longer than 3.8 seconds before being accosted by the male. Not so easy to evaluate a mating display in that time.

This, on the other hand, is a Satin Bowerbird (Ptilonorhynchus violaceus) courtship arena. It’s not a nest, but a structure built by the male called a bower. When the female comes to visit, she sits right in the middle.

The male displays out front and she will often spend several minutes evaluating his display. If the male wants to attempt mating, he has to go around to the back of the bower, giving the female an opportunity to escape out the front. Fascinatingly, it appears that the bower structure functions specifically to protect females from coercive mating.

We suggest that, instead of evolving direct resistance to unwanted male advances and touching off an arms race, females can actively remodel males, that is, change the males themselves, by evolving mate preferences for male traits such as the protective bowers that enhance freedom of mate choice – even though the bower is likely costly to males and hinders their coercive mating opportunities.

To explore this, we built a theoretical, proof-of-concept model where females can evolve to first choose what kind of bower to visit in order to then evaluate a male’s display

We show that, under certain sets of conditions, when male bowers are protective to females, bowers, and the female preferences for them, can invade and persist in the population in spite of the costs due to their utility in enhancing females’ sexual autonomy. Indeed, you can see in that in this model simulation, the attractive male display trait in the population, shown as the warmness of the color, concurrently increases because females are getting what they want more often.

Obviously, a striking aspect of this is the oscillations.

As bowers come into the population, fewer matings are coerced, and females with a preference for bowers get an advantage by mating more often with attractive males, as shown by the orange line. However, the protective bowers are out there in the population now, and can act as a “public good.” Females without a preference for protective bowers (the blue line) can freeload, reaping the benefits of increased freedom of choice without paying any of the costs of specifically seeking out bowers, and so they become favored briefly until bowers decrease again. Eventually it converges on an equilibrium where overall males rarely coerce and females have substantially increased ability to choose mates.  

Although the bowerbirds are a useful example, the “remodeling” process could gain purchase in any scenario where preferences can act on multiple scales allowing females to avoid direct coercion. For example, in the paper, we speculate that such a process could represent an alternative (or complementary) underlying mechanism for hominid “self-domestication,” wherein females forming friendship coalitions or choosing to associate with males with outward traits uncorrelated with aggression could have led to modern levels of reduced coercion and infanticide, and reduced sexual dimorphism in traits such as body size and canine teeth.

Photo Credits: 

  • Duck genitals: Dr. Patricia Brennan
  • Tooth-billed Bowerbird court: Macaulay Library ML278241221
  • Satin Bowerbird Bower: Dr. Hazel Parry
  • Satin Bowerbird Courtship video: Carlo Ferraro (
  • Chimpanzee: Ronan Donovan

New paper out! An anomalous Red-winged Blackbird song

In this natural history note published in the Canadian Field-Naturalist, colleagues and I describe a “highly anomalous” song we heard while out birding in a marsh around Ottawa, Ontario. The very strange two-note song piqued our interest, and we were surprised to see it coming out of a male Red-winged Blackbird doing a typical territorial display, but sounding not at all typical! We recorded it on two separate occasions- you can listen to what it sounded like here on left, recorded by lead author Brandon Edwards and accessioned in the Macaulay Library. Compare the sound and spectrogram to a more typical song on the right:

The anomalous Red-winged Blackbird song

A “typical” Red-winged Blackbird song

In the paper we review the various possible causes for aberrant bird song known in the literature, including malnourishment while young. We speculate that in this case, however, the bird was likely deaf from a young age. Though this is possibly just one idiosyncratic example, this highlights the importance of always being on the lookout for new and strange things around you- each little natural history note contributes to a constellation of data points that can show us how the world is changing or how our original thinking might be wrong!

New Position at IAST, France

In September 2021, I made a big move across the ocean to the Institute for Advanced Study in Toulouse (IAST) for a Postdoctoral Research Fellowship. The IAST, a part of the Toulouse School of Economics, is a broadly interdisciplinary institute with the unified goal of studying and understanding human behavior, evolution, and our place in the world. Faculty, fellows and visitors include Economists, Political Scientists, Psychologists, Anthropologists, Historians, Sociologists, and of course, some Evolutionary Biologists! I’m excited to contribute to and learn from this fantastic community of diverse scholars over the next couple of years in beautiful Toulouse! I will be continuing to work on sexual selection and sexual conflict theory, while also building collaborations and new applications for dynamic social network models.

Check out this fantastic interview video the media team put together where I talk a bit about my research and about Toulouse!

My PhD Defense!

I am pleased to announce that I successfully defended my PhD dissertation on October 19, 2020! After a leave of absence due to a traumatic brain injury (I’m doing a lot better now!), and then delays due to COVID, I am so, so grateful to have arrived at the point of finishing my doctorate.

At first I was disappointed that it had to happen over Zoom in classic pandemic style, but I have to say that there are several advantages to the increased accessibility that comes along with the format. Friends, colleagues, and loved ones from all over the world were able to attend (far more than would have been able to make the trip to New Haven on a weekday!), and as an added bonus, my public talk could be recorded and now shared here!

Thanks so much to my PhD advisor Dr. Richard Prum for his flattering introduction and to my committee, Drs. Maria Servedio, Suzanne Alonzo, David Vasseur, and Tom Near, as well as to my collaborators on the featured Sage Grouse work: Drs. Gail Patricelli, Alan Krakauer, and Anna Perry, Ryane Logsdon, and Dr. Carter Butts.

For sexual behavior, math, networks, and birds: