Your Cheating Heart

Scientists take a clinical view, reminding us that monogamy is rare in the animal world

• Mark Cheater
• Feb 01, 2003

VALENTINE'S DAY is a time for poets and romantics to wax eloquent about true love. Scientists take a more clinical view, reminding us that monogamy is rare in the animal world. A recent study of shorebirds points to a possible reason for infidelity: It's for the kids' benefit.

Scientists took a look at western sandpipers, common sandpipers and Kentish plovers in nesting grounds in Alaska, Sweden and Turkey. They examined the DNA of both parents and chicks, and found as many as 20 percent of offspring were the result of "extra-pair copulations," i.e., infidelity. When they compared the DNA of each set of mated pairs, they discovered that the more closely related mates were, the more likely they were to seek out other partners.

"What appears to be going on is that the infidelity is a direct result of avoiding inbreeding," says Brett Sandercock, a biologist at Kansas State University. Since inbreeding generally reduces the survival of offspring (avian and otherwise), infidelity may be a useful strategy to increase the odds of having healthy progeny.

Who says cheaters never prosper?