Why do we age? For evolutionary biologists and geneticists, it's still a mystery. One of the leading theories, called "antagonistic pleiotropy," has it that a single gene might control for two traits: one that makes you more reproductively successful when you're young, while also setting the stage for your death when you're older. For example, high testosterone is good for men while they're oat sowing, but worse when they're older because it confers a greater risk of prostate cancer.
A new study published online this week in Nature explains a particularly fun and straightforward example of the phenomenon: horn size among male rams. The researchers, from the University of Edinburgh, looked at Soay rams, a primitive breed found on a remote island off the coast of Scotland. They found that rams with two copies of the gene for big horns fathered twice as many lambs as rams with two copies of the gene for small horns, but were also significantly more likely to die each winter. It was the rams in the middle, though, who were the real winners- males with one copy of the big horn gene and one copy of the small horn gene had big horns, made a lot of babies, and lived for a long time. Win. Win. Win.
The study helps to explain why we find such diversity within a species, even when some traits clearly make individuals more sexually competitive than others. In the club, it helps to be big like Shaq or beautiful like Brad Pitt, and on the elementary school playground, no one wants to be the pipsqueak. But if, when school starts, your child finds himself the target of a big, bad bully, you could teach him this retort (which is an unproven extrapolation from the rams study): Sticks and stones may break my bones, but I might live longer than you.
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Leon Neyfakh is the staff writer for Ideas. Amanda Katz is the deputy Ideas editor. Stephen Heuser is the Ideas editor.
Guest blogger Simon Waxman is Managing Editor of Boston Review and has written for WBUR, Alternet, McSweeney's, Jacobin, and others.
Guest blogger Elizabeth Manus is a writer living in New York City. She has been a book review editor at the Boston Phoenix, and a columnist for The New York Observer and Metro.
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Guest blogger Joshua Glenn is a Boston-based writer, publisher, and freelance semiotician. He was the original Brainiac blogger, and is currently editor of the blog HiLobrow, publisher of a series of Radium Age science fiction novels, and co-author/co-editor of several books, including the story collection "Significant Objects" and the kids' field guide to life "Unbored."
Guest blogger Ruth Graham is a freelance journalist in New Hampshire, and a frequent Ideas contributor. She is a former features editor for the New York Sun, and has written for publications including Slate and the Wall Street Journal.
Joshua Rothman is a graduate student and Teaching Fellow in the Harvard English department, and an Instructor in Public Policy at the Harvard Kennedy School of Government. He teaches novels and political writing.