Female Zebra Finches May Inherit Infidelity Gene From Cheating Fathers

Weiner, Schwarzenegger and ... Zebra Finches?

A new study published in the current edition of Proceedings of the National Academy of Sciences shows that monogamy might not even be for the birds.

For eight years, behavioral psychologist Dr. Wolfgang Forstmeier and his colleagues at the Max Planck Institute for Ornithology in Seewiesen, Austria, observed the mating habits of over 1500 zebra finches in the Institute's aviaries.

What they learned was surprising. Although birds are natural monogamists, pairing off with one mate for life, that doesn't prevent them from cheating with other birds.

"[Finches] find a partner and stick with it forever," Forstmeier told The Huffington Post. "But it appears that [while this partnership exists] on a social level where they build nests together, it has nothing to do with copulation."

This is no big deal for the male finches; promiscuity only increases their chances of reproductive success. The lady finch, on the other hand, potentially loses more than she gains by sleeping around -- unlike the male, she can only reproduce with one bird at a time (her mate or another partner), and her cuckolded partner might abandon her chicks.

When Forstmeier's team conducted paternity tests on each bird, things got even more interesting. They found that male finches with a penchant for "cheating" had daughters with a proclivity for infidelity as well, suggesting that female songbirds may inherit what the scientists deemed a "Casanova gene" from their fathers.

This study suggests that even though "unfaithful" behavior is risky for female birds, infidelity persists in both sexes because the biological advantages for the female finch's father and male offspring outweigh any disadvantages for the female herself.

One question the research raises is whether humans might also blame unfaithfulness on the sins (or underlying genes) of their fathers.

There's no conclusive evidence of a gene that predisposes human beings to infidelity, but a study published in the online science journal PLoS One last year suggested the possibility. That study, headed by Justin Garcia, an evolutionary biologist at Binghamton University, found that individuals with a certain variation of a gene responsible for dopamine receptors were more likely to participate in uncommitted sex, including infidelity.

Garcia said he is excited by the results of the songbird study.

"It is very promising and very interesting, because we are getting closer to understanding the biological foundation of mating and reproduction," he said.

Still, Garcia warned that humans cannot blame their behavior entirely on their genetic makeup.

"As humans, we are never imprisoned by our biology," Garcia said. "We have brains to make decisions. But it does provide evidence that biology can contribute to sexual behavior."

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