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Infidelity is easy to explain in males. By sleeping around, a guycan potentially impregnate more females and sire more offspringthan if he just had one mate. But females cheat, too, even though awoman will only be able to have roughly one baby per year no matterhow many male sex partners she has had. One leading evolutionary hypothesis suggests that a female whomates with multiple males ensures the genetic diversity and qualityof her offspring; having higher-quality offspring couldtheoretically give her more grandchildren later. A 17-year study , published in the June issue of The American Naturalist,challenges this hypothesis. "This is one of the most careful and most robust studies toexplore whether polyandry is adaptive in females," saysTommaso Pizzari, a University of Oxford biologist who was notinvolved in the research. "The answer is: not really." Previous studies tested the "quality" hypothesisindirectly. In socially monogamous species, researchers wouldcompare the legitimate and illegitimate offspring of cheatingfemales by asking: Which offspring were larger? Which lived longer?But a better way to understand why female promiscuity evolved, saysJane Reid, a biologist at the University of Aberdeen in Scotlandand author on the new study, is to determine whether thoseillegitimate offspring actually have more babies. Reid and her team studied the isolated population of wild songsparrows on Mandarte Island in Canada. Like their mainlandcounterparts, these birds are socially monogamous. Males andfemales pair up for an entire breeding season or for severalbreeding seasons, and work together to feed the hatchlings anddefend the nest. But they're not always faithful; blood testsshowed that in this particular population, 28 percent of hatchlingswere fathered by other males. The researchers studied three generations of song sparrows(including more than 2,300 hatchlings) to see whether the cheatingfemales' illegitimate sons and daughters would have higherreproductive success. It turned out that the bastard hatchlingsactually fared worse than their legitimate siblings, producingabout half as many offspring, on average. "It's not whatpeople expected," Reid says. David Westneat, a behavioral ecologist at the University ofKentucky, agrees. "It's essentially saying that there's noevidence for a hypothesis that's been very popular." But thetheory is not dead yet, because the results need to be confirmed inother populations and other species. Westneat and Pizzari alsoexpressed some concern over the fact that the study took place onan island—these small and isolated populations have atendency to evolve in weird ways. Nevertheless, the scientists agree that female promiscuity does notappear to have reproductive advantages for most of the female songsparrows on Mandarte Island. So what's the point of cheating, if itdoesn"t help them to have greater evolutionary success? Some theories blame it on the boys: Female promiscuity may be anecological by-product of male promiscuity. If males are understrong selection to mate with multiple females, then in a closedenvironment females might be forced to mate with multiple males. Reid is also investigating whether female promiscuity is a genetic by-product of the male version. If there are genes that encourage a male tobe promiscuous, he might pass those genes on to his daughters, eventhough they may not benefit from the behavior. A recent study in zebra finches found support for this hypothesis. If it turnsout that genetics have a heavy influence on feminine infidelity, Reid's team wouldlike to try to pin down which genes are contributing to promiscuousbehaviors. The e-commerce company in China offers quality products such as Pneumatic System Components , China Pneumatic Solenoid Valves, and more. For more , please visit Pneumatic Tube Fittings today!
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