When she and her team conducted paternity tests on bluebird nestlings, they hit “pay dirt,” she said: Some chicks had DNA that aligned with mom’s DNA but not with that of her nesting partner.

As many as 20 percent of nestlings in Gowaty’s field sites are sired by one father and raised by another, contradicting scientists’ previous estimates that in 90 percent of socially monogamous songbirds, females were sexually monogamous. Within a decade of Gowaty publishing her findings, other scientists were estimating that female sexual monogamy occurred in just 10 percent of those species. (See bluebird sidebar.)

In studying mate-choice consequences, UGA researchers (L-R) Yong-Kyu Kim, Patricia Gowaty and Wyatt Anderson have shown that mutual attraction between mom and dad fruit flies leads to healthier young that are more likely to survive.

As Gowaty pondered the effects of females seeking extra partners — what scientists call “extra-pair paternity” — she saw potential evolutionary advantages. For one, a songbird mom who mates with multiple partners could broaden genetic variation among her nestlings. The greater the genetic dissimilarity between mom and a partner, the greater the possibility that young from that union will be better equipped genetically to withstand attacks from pathogens and parasites, for example. And that ultimately could spell the difference between life and death among step-siblings. Additionally, while some male sexual partners could lead to higher innate fitness in offspring, others might offer better parenting behaviors that could increase nestling success.

At that time, scientists generally considered male behavior patterns to be the primary determinant of a couple’s success and survival. But Gowaty reasoned that if female behaviors have effects on fitness, such as the number of kids produced, they also could influence natural selection. In 1994, she voiced her ideas — most of them not previously entertained by other scientists — at an international ecology meeting. The response was a buzz of skepticism. Undeterred, she organized a symposium to explore the interface between feminism and evolutionary biology and to examine evolutionary consequences of male and female behavior. Seizing the opportunity to develop a “more inclusive evolutionary biology,” Gowaty compiled a diverse collection of papers and essays — some from the symposium and others in response to it — for the book Feminism and Evolutionary Biology, published in 1997.

Gowaty also became even more convinced she must show that both sexes contribute to natural selection through mate-choice behaviors. However, she faced a problem of numbers: Polygamous males can sire many families during a breeding season, but females lay about the same number of eggs regardless of how many partners they have. How would female and male mate choice make an evolutionary difference?

As 1994 drew to a close, she had the answer: Forget about the number of offspring and find out whether mating with a partner of choice affects offspring quality. “At the time, I didn’t know the answer and nobody else did either,” Gowaty said. And to get it, she would need something other than bluebirds. She needed a wild, and therefore genetically diverse, creature that matures quickly and thrives under laboratory conditions. The lowly but serviceable fruit fly seemed perfect. For advice on raising these diminutive insects, she turned to Wyatt Anderson, a UGA Distinguished Research Professor of Genetics, whose fruit-fly genetics studies had spanned more than three decades.