Parasites and the Red Queen's Race

The Red Queen is a character in Lewis Carroll's Through the Looking-Glass, who has to run as fast as she can just to stay in one place. Biologists use the term "Red Queen's Race" to refer to the process by which species must evolve and adapt just to cope with day-to-day threats which are evolving equally rapidly to overcome their countermeasures.

One of the most common sorts of Red Queen's Race is the battle between a host organism and its parasites. The host evolves new ways to repel or destroy the parasites, while the parasites come up with ways to evade the host's immune system. Of course, if the host devotes too much of its resources to stopping parasites, it becomes uncompetitive in other ways -- to change analogies, the host is like a country. Does it spend money coming up with weapons to fight its enemies, or spend it on economic development?

Here's a great example of one such race in action. Snails in New Zealand have to fight off parasites, which means they need to evolve as fast as the parasites do, even though the parasites probably have a faster reproductive cycle than the host snails do. But the snails can make use of a powerful ally:  SEX. (I did that to help our Google search results.)

Sexual reproduction is a great way to jazz up your genetic diversity, helping you evolve better. The snails which are afflicted with parasites are more interested in finding sex partners so they can perform sexual reproduction -- and thereby give their offspring a marginally better chance of fighting the parasites. Snails with no parasites aren't interested in the dating game, and reproduce asexually.

I don't know if this would help humans looking to attract a partner, but it might be worth a shot:  "Hey, sweetie! My genes may help your offspring avoid deadly parasites! Wanna go back to my place and watch Firefly reruns?" Try it and see!