Boy Meets Girl...
SciWorks Radio is a production of 88.5 WFDD and SciWorks, the Science Center and Environmental Park of Forsyth County, located in Winston-Salem.
What was it that attracted you to your mate? How did they impress you? Humans aren’t the only animals that work hard to attract a partner, in fact it happens throughout the animal kingdom. Often it works like this: Boy meets girl, boy hisses, flaps, or rams his horns against another boy to impress girl. Girl either accepts or rejects boy.
Baby animals are made… or not. How has evolution produced these often strange and sometimes beautiful mating rituals? To find out I spoke with Dr.Matthew Fuxjager, Assistant Professor of Physiology in the Department of Biology at Wake Forest University.
I study how birds perform elaborate dance routines for courtship and other social interactions. How those behaviors evolve and how the physiology of the bird has evolved to accommodate some of those unusual behaviors that they show that they wouldn't otherwise normally perform in the wild to fly or to forage or do anything like that. In particular I study manikins. These are tropical birds and there's about sixty species within the family and all the species produce very different kinds of elaborate kinds of displays. These animals perform these displays for two purposes. One is to attract a mate, and the second is to fight with other males. They all come together and they display, and a female will come along and she'll look at a lot of these different males and see who she likes the best based on his display performance. If it's just males at these large groups in the forest, they’ll actually display to one another, and have these little display-offs that you'll see in the forest. We think it's a competitive thing but it's also sexual thing.
With natural selection, the the lineage of a species is determined by its ability to adapt to its environment. You probably learned about this in school. Another evolutionary force, which receives less attention, is sexual selection. This is where the lineage of a species is driven by what individuals find attractive. If I am born with beautiful purple feathers, and females prefer that, future generations are more likely to have beautiful purple feathers, like mine. So, how can sexual selection influence the type of mating rituals found in animals?
What we think is happening is that of evolutionary time sexual selection is shaping the neuromuscular system in a way so that it corresponds to hormones that control sex and reproduction. This is one way we think that evolutionary forces are able to influence gestural motor movements and shape them in sexual context.
And if you’re wondering why it's often males working hard to impress females, here’s some possible insight.
Testosterone seems to be an important part of this evolution, and of these acrobatic displays. The species with the more complex displays have muscles and spinal cord tissue that's more sensitive to testosterone. So testosterone is more likely to act there, and has a greater effect on those tissues. And that seems to be underlying some of the diversity and the variation in terms of behavior that we’re seeing. The testosterone can turn up or turn down the regulation of certain genes in these muscles. And ultimately that changes the composition of the muscles and you can start to produce substances in the muscles that allow the muscle to actually contract and relax faster than it would otherwise. We also are finding that testosterone is changing the molecules and the proteins in the muscle that allow the muscle to grow and to get stronger and bigger and those sorts of things.
In fact, Dr. Fuxjager has found that these muscular adaptations are also passed on to female manikins. They don’t perform mating dances in the wild, but when testosterone is added to their bodies in the lab they move like males do during courtship. This shows that the traits are passed down through both the males and females of the species.
So, what about animals that aren’t birds?
I use birds as a model but this is what's so exciting about the work, looking at how evolution can shape neuromuscular systems to influence movements in sex. We see these elaborate displays across all different kinds of animals where the males perform these crazy movements We find this in mammals we find it in frogs we find it in birds we find in fish. We see this everywhere in all sorts of different animals.