 So, if you're going to claim that sex increases genetic diversity with the goal of reducing susceptibility to parasites, then you'd have to somehow make the link between what people find sexy and whether or not that actually indicates parasite free-ness. And it's true, they found that old boy Peacock here has his amazing, gorgeous feathers if he had parasites. Then he... all of his food, all of his energy, all of his time is going to be spent eating to feed his parasites. And he's not going to have the energy or the resources to build that phenomenal tail. They've looked at Peacock immune systems and found that, yeah, the cooler your tail is, the stronger your immune system is. And the ladies use the tail as evidence for the strong immune system that's resistant to parasites. This encourages a genetic, what? Like, set of cards or genetic compilation that encourages that parasite free immune system. They've looked at some fish and these fish or even our little birds here who are building their crazy tunnels or their crazy displays for the ladies. If you are having to maintain a population of parasites in your gut, then, dude, you're not going to have the energy to go around and find all those blue things to make the pretty little display for the ladies to impress them. So, you're not going to have the energy to pull it off. The ladies that or the fellows that are most attractive to the ladies, it has been confirmed, are the displays that they're putting forth are correlated with lower parasite infections. Isn't that phenomenal? Okay, so let's just take a little moment to look at the parasites. What are parasite strategies and how are the parasites involved in this whole thing? And then we're going to look at a parasite runway where we're going to give a big shout out to the cool parasites out there because there are a bunch of them.