The Elephant in the Room is Female: Sex Bias in Behavioral Science

“You run like a girl!” is a (misogynistic) insult.

But what about “You strangle your male mate, beat yourself against rocks, and starve yourself to death like a girl!” – a female octopus, to be exact? (Wood, 2018)

Many female animals showcase behaviors that are violent, gruesome, or sexually promiscuous: decidedly un-“ladylike” behaviors (Cooke 2022). However, 20th century science (especially ethology, the study of animal behavior) was unfortunately steeped in sexism, coloring the achievements and findings of Western scientists. Some of these bizarre female behaviors therefore went undetected and unstudied. In response, a new generation of feminist scientists, including zoologist Dr. Lucy Cooke and biologist Dr. Zuleyma Tang-Martinez, are challenging the narratives proposed for centuries (Cooke 2025, Hunt 2022, Tang-Martinez 2017). They are starting with the father of evolution: Darwin himself.

Many may know Darwin as the ‘finch guy,’ or the man who coined “survival of the fittest,” also known as Darwin’s theory of natural selection. In fact, his doctrine was so widely accepted by the early 20th century that natural selection was deemed the basic mechanism of evolution, and the “unifying theory of the life sciences” (“Charles Darwin,” 2024).

Thus, Darwin paints a very clear picture: male animals aggressively vie for a passive female, who is then seduced and mated by the dominant male. However, this characterization isn’t the most complete. Darwin omits many nuances in the world of animal behavior, which is far from blackand-white.

One example of such nuance is bird song. Singing is traditionally thought of as a male bird trait: males sing to attract females, defend territories, and identify themselves to other birds (Thompson 2014). While generations of ornithologists noticed that female bird song did exist, male bird scientists were unwilling to study it. For example, out of 1,000 publications on the barn swallow, not a single paper studied female song until a group of female researchers released the very first study in 2020 (Wilkins et al. 2020). They found that female birds sing for many of the same reasons as males, and that it was actually easier to tell males and females apart by their songs rather than their colors, which indicates that song in female birds is distinct (Wilkins et al. 2020, Benedict and Wilkins 2021). They also found that song and plumage characteristics can better predict reproductive success in females, suggesting that a female’s song and feathers play an important role in finding a mate (Wilkins et al. 2020, Benedict and Wilkins 2021). If female bird song and color are important for reproduction, they must have an evolutionary purpose for these secondary sex characteristics—a finding that, according to Darwin, would have been impossible. New research also shows that female ancestors of modern-day birds probably also sang, indicating that song evolved commonly across birds of all genders, not just males (Omland et al. 2021, Wilkins et al. 2020). Now, scientists are questioning why females lost song, rather than why males evolved it. Thanks to the women who led these groundbreaking projects, scientists are reframing their studies of birds from new perspectives.

Another instance of black-and-white assumptions in animal behavior is the long-perpetuated stereotype of male promiscuity and female monogamy: the idea that males evolved to mate with as many females as possible, while females evolved to mate with only one male. Darwin noted that promiscuity in animals exists, but only mentioned male behaviors (Cooke 2022). Angus Bateman, a botanist, would ultimately support the theory of male promiscuity with data. Bateman found in reproductive experiments using Drosophila fruit flies that males have more offspring when they mate with multiple females, while the “peak of female reproductive success” is after mating with only one male (Bateman 1948, Cooke 2022, Tang-Martinez 2017).

Bateman used these results to argue that “males will be expected to show polygamous tendencies, whereas in females there would be selection in favour of obtaining only one mate, after which they would become relatively indifferent” (Bateman 1948, Cooke 2022, Tang-Martinez 2017). The problem is that this is only half of Bateman’s data. The other half, revealed by Cooke and TangMartinez, shows that the more times a female fly mates with a male, the more offspring she has: in other words, promiscuity also benefits the female (Cooke 2022, Tang-Martinez 2017). But Bateman’s second graph was largely ignored, and the promiscuity myth spread throughout the field of animal behavior.

Though there are certainly many animal species with promiscuous males and monogamous females, we now also know of cases where female animals are just as promiscuous as males. Female lionesses will mate with a male 20-40 times per day while in heat, with the female initiating these copulations and often mating with multiple male partners (Thornberry 2021, Cooke 2022). Many “monogamous” male and female birds will “cheat” on their partners; up to 40% of young in many North American birds are from other fathers (Stutchbury 2010). Patricia Gowaty, the first scientist to use paternity testing on bird eggs, found that birds of both sexes, not just males, are cheaters. She recalled in an interview with Cooke that her findings “…offended so many people that it was unbelievable. They couldn’t imagine that females were anything but benign” (Cooke 2022, Incorvaia 2023).

Gowaty’s experience highlights that even when data calls stereotypes and assumptions into question, scientists will ignore or even deny observations that go against the status quo. Darwin himself saw “exceptions” to the rules in his work, noting that calico coloring in cats is exclusive to the females, and that certain hen species are more aggressive and brighter-colored than roosters, but ultimately chalked these up to outliers and never investigated further (Darwin 2009). On birds specifically, a 1992 study on aggression expected to find aggressiveness in males. When they found instead that females engage in significantly more fights than males, the all-male team was perplexed. However, rather than investigating further, they completely dismissed the behaviors (Lawton et al. 1997, Tang-Martinez 2017). Thus, bias in science has actively prevented scientists from investigating interesting observations in the field.

Luckily, the rise of women in science is introducing all-new perspectives in animal behavior and other related fields. The new wave of feminism in science could be the key to understanding science in a whole new way, bringing justice for centuries of unexplored, yet important, female behaviors. Were it not for the female scientists who dared to challenge the norms of behavioral science, we likely would have never known that female birds sing and are promiscuous, too. Intersectionality between female scientists and queer researchers has even led to new studies on homosexuality in animals, disputing the idea that heterosexual behaviors evolved first (Lawton et al. 1997). The rise of new voices in science in the 21st century has highlighted the importance of bias removal in science. Being a good researcher means seeking the truth, even when the truth is uncomfortable or leads to more questions. As Darwin himself says, “The love for all living creatures is the most noble attribute of man” (Darwin 1871). That includes female creatures, too.

Those interested in learning more should read Bitch: On the Female of the Species by Lucy Cooke, and take Dr. Alison Pischedda’s Animal Behavior course at Barnard!

References

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