The propagation of every animal on the planet is the result of sexual activity between males and females of a given species. But how did things get this way? Why two sexes instead of one? Why are sperm necessary for reproduction and how did they evolve? These as-yet-unresolved issues fascinate Timothy Karr, a developmental geneticist and evolutionary biologist at Arizona State University's Biodesign Institute. To probe them, he uses a common fruit fly, Drosophila melanogaster -- an organism that has provided science with an enormous treasure-trove of genetic information.

"My research focuses on the evolution of sex and in gamete function," Karr says. "I focus primarily on the sperm side of the sexual equation. I'm interested in how they originated and how they are maintained in populations."

Read more at E! Science News.