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This is Scientific American's 60-Second Science. I am Karen Hopkin, this will just take a minute.

If you’ve ever given any thought to the life style of the hermaphrodite, it’s probably occurred to you that being both male and female¹ doubles your chances of having a date on the Saturday night. Yeah it’s an old joke, but it's sort of true. Because most hermaphrodites do have to date. In other words, they can't simply fertilise themselves. If they could, I am sure they would. So what actually stops them? I mean what keeps hermaphrodite from mixing together its own sperm² and eggs and then staying home to watch TV? In the March 20 online issue of Science, researchers from Japan revealed³ the answer. They were studying the sea squirt, an animal that reproduces⁴ by spewing sperm and eggs into the water and leaving the rest to chance. Combing through the sea squirt genome, the Japanese scientists discovered two sets of genes⁵, one produces a protein found on the egg’s surface, the other makes a similar protein on sperm. When these molecular⁶ calling cards held from different animals, the proteins come together and allow fertilization to occur. when they are from the same animal, they politely shake hands and go to separate ways. Now if only humans had such a simple system for figuring out who to bring home to mother.

Thanks for the minute, for Scientific American's 60-Second Science, I am Karen Hopkin.