Evolutionary Biology: Gender-Aware Guidelines

Research may embed gender-biased assumptions and stereotypical thinking. This method develops guidelines for research in evolutionary biology to guard against such biases when working with questions related to sexual reproduction and sexual dimorphisms in animals and other non-human organisms.

A workshop designed to approach gender-bias in evolutionary biology publications developed a critical axis to identify: 1) biased assumptions, 2) biased inferences and reasoning, and 3) gaps in the literature; and a constructive axis to advance good-research guidelines.

This workshop, held at Uppsala University, Sweden, in 2018, resulted in a set of guidelines aimed at reducing gender-biased assumptions in evolutionary biological sciences (Ahnesjö et al., 2020). These guidelines are reproduced in short form here.

“Gender-biased assumptions” are defined as assumptions applied to the sexes based on stereotypical, socio-culturally defined views of gender.

1. Be aware of your Assumptions.
Avoid gender-biased assumptions about a priori sex differences in animals, and reflect upon “taken-for-granted” views of female or male traits in each stage of the scientific process.
  • a. Gender-biased assumptions may have an impact on different stages of the scientific process and a critical reflection on a priori sex differences is thus recommended in all stages. Gender-biased assumptions may appear when conceptualizing ideas, making predictions, and framing theories. These assumptions often appear in introductory sections, where sex differences in animals often appear as general trends without sufficient literature support (for example, “competitive” males and “choosy” or “caring” females—when, in fact, both sexes can display these behaviors). It is crucial to be open to the diversity of outcomes in experimental and theoretical research, especially the diversity of what males and females of various species do in nature. We argue that even well-supported general trends may encounter exceptional behaviors in nature that should not be overlooked. We argue further that differences—as well as similarities—between and across the sexes is important to present in qualitative and quantitative ways (for balanced examples, see Clutton-Brock 2007; Rosenthal 2017; Hare and Simmons 2019).
  • b. In data collection and experimental design, use “naïve” experimenters (i.e., experimenters uninformed about predictions, treatments, and sex of the organism), whenever possible, to avoid introducing bias. This is especially important in behavioral studies, where observers may carry unconscious assumptions about expected male or female behaviors. Also be aware that, when collecting data, researchers may pay more attention to findings that confirm what they believe to be true. Dominant animal model systems may prompt confirmation biases (Zuk, et al., 2014).
2. Be Transparent. Support transparency as part of the scientific process and key to good research practice.
  • a. Provide scientific support for the assumptions made about the sexes, and acknowledge and address critical scientific debate that exists in the literature. Avoid fallacies, such as “appeal to authority” and confirmation bias, that may limit the ability to recognize diversity and variation among the sexes. For example, in evolutionary biology, the long established argument that female and male sexual traits and behaviors result from anisogamy, i.e., the fusion of a large egg and small sperm—as put forth in the Bateman-Trivers paradigm (Bateman, 1948; Trivers, 1972)—is an appeal to authority. Researchers should also openly present critical debates surrounding these arguments (Snyder & Gowaty, 2007; Tang-Martinez, 2005).
  • b. When designing an experiment, present your arguments for a chosen design, especially when only one sex is studied or when the methods differ for the sexes. This will allow the readers to assess whether the design embeds gender-biased assumptions. Where feasible, measure the same parameters in the same way in all sexes. If only one sex is studied, specify which sex and provide the rationale for why. When measuring sex-specific traits, reflect openly about the relevance and the comparability between sexes.
3. Be Aware of Language Usage.
Be aware of and careful in the choice of words, metaphors, and anthropomorphic terminology in relation to sex, as they may carry normative implications and may mislead a reader into gender-biased assumptions (see Method: Rethinking Language).
  • a. Language itself can be gendered (Beldecos et al., 1989), and its use is a powerful tool that requires care and precision. It has been well documented, for example, that, when describing similar behaviour, female animals often are described as passive while males are described as active (Bertotti Metoyer & Rust, 2011; Karlsson Green & Madjidian, 2011).
  • b. Language can embed metaphors that carry normative implications beyond what the evidence may show (Hankinson Nelson, 2017). To guard against this, use descriptive, neutral, and operational language, especially where metaphors or shorthand terms rely on readers’ cultural expectations—see Table 1. A simple self-test can be to switch male and female terms. If the meaning of the sentence is changed beyond the simple change of sex, the wording may be gender-biased.
Table 1. Two examples of anthropomorphic language and suggested terminological alternatives.

Anthropocentric terminology Recommended alternatives
(MacFarlane, Blomberg, & Vasey, 2010)
Use the descriptive term “same-sex” (Scharf & Martin, 2013)
“Sex-roles” or “reversed sex-roles” (e.g. Forsgren, Amundsen, Borg, & Bjelvenmark, 2004; Hare & Simmons, 2019; Lehtonen, Parker, & Schärer, 2016) Use “courters” and “choosers” as operational descriptors, independent of sex (Rosenthal, 2017) or just describe operationally what females and males do without ascribing them “sex-roles” (Ah-King & Ahnesjö, 2013)

4. Be Careful When Generalizing.
Be clear and careful when generalizing results. Scientific rigor should be applied to: 1) ensure representative sampling of the sexes; 2) unbiased trait measurements; and 3) evaluation of alternative hypotheses.
  • a. Both female and male animals should be used in representative numbers for data collection, and data should be analysed by sex (Shansky, 2019). Females have historically been understudied. In the study of animal genitalia, for example, female genitalia remains understudied (Ah-King et al., 2014). Studies can be designed to investigate the previously underrepresented sex, where relevant.
  • b. Studies done in one sex should not be generalized to other sexes.
  • c. Explanatory frameworks should not exclude less common findings in a particular sex; rather variations should be acknowledged. Sexual selection research, for instance, has historically focused more on males than females and focused on extravagant traits used in mating competition (both competition for access to mating partners and competition to be chosen as mating partners). This asymmetry can be seen in textbooks, where illustrations feature a higher number of male than female animals (Fuselier et al., 2018). Recent literature, however, has shown sexual selection is not confined to one sex (Clutton-Brock, 2007; Hare & Simmons, 2019).
For the fun research paper, see: Ahnesjö, I., Brealey, J. C., Günter, K. P., Martinossi-Allibert, I., Morinay, J., Siljestam, M., Stångberg, J. & Vasconcelos, P. (2020). Considering Gender-Biased Assumptions in Evolutionary Biology. Evolutionary Biology, 47(1), 1-5.

Works Cited

Ahnesjö, I., Brealey, J. C., Günter, K. P., Martinossi-Allibert, I., Morinay, J., Siljestam, M., Stångberg, J. & Vasconcelos, P. (2020). Considering Gender-Biased Assumptions in Evolutionary Biology. Evolutionary Biology, 47(1), 1-5.

Ah-King, M., & Ahnesjö, I. (2013). The “Sex Role” Concept: An Overview and Evaluation. Evolutionary Biology, 40(4), 461–470. https://doi.org/10.1007/s11692-013-9226-7

Ah-King, M., Barron, A. B., & Herberstein, M. E. (2014). Genital Evolution: Why Are Females Still Understudied? PLoS Biology, 12(5), 1–7. https://doi.org/10.1371/journal.pbio.1001851

Bateman, A. J. (1948). Intra-sexual selection in Drosophila. Heredity, 2, 349–368.

Beldecos, A., Bailey, S., Gilbert, S., Hicks, K., Kenschaft, L., Niemczyk, N., … Wedel, A. (1989). The importance of feminist critique for contemporary cell biology. Feminism and Science, 3(1), 172.

Bergvall, V. (2014). Rethinking language and gender research: Theory and practice. Routledge.

Bertotti Metoyer, A., & Rust, R. (2011). The Egg, Sperm, and Beyond: Gendered Assumptions in Gynecology Textbooks. Women’s Studies, 40(2), 177–205. https://doi.org/10.1080/00497878.2011.537986

Clutton-Brock, T. H. (2007). Sexual selection in Males and Females. Science, 318(5858), 1882–1885. https://doi.org/10.1080/09540121.2012.701726

Daly, M., & Wilson, M. (1983). Sex, evolution, and behavior (2nd ed.). Boston: Willard Grant Press.

Forsgren, E., Amundsen, T., Borg, A. A., & Bjelvenmark, J. (2004). Unusually dynamic sex roles in a fish. Nature, 429(6991), 551–554. https://doi.org/10.1038/nature02562

Fuselier, L., Eason, P. K., Jackson, J. K., & Spaulding, S. (2018). Images of Objective Knowledge Construction in Sexual Selection Chapters of Evolution Textbooks. Science and Education, 27(5–6), 479–499. https://doi.org/10.1007/s11191-018-9978-7

Hankinson Nelson, L. (2017). Biology and Feminism, a philosophical introduction. Cambridge University Press.

Hare, R. M., & Simmons, L. W. (2019). Sexual selection and its evolutionary consequences in female animals. Biological Reviews, 94, 929–956. https://doi.org/10.1111/brv.12484

Karlsson Green, K., & Madjidian, J. A. (2011). Active males, reactive females: Stereotypic sex roles in sexual conflict research? Animal Behaviour, 81(5), 901–907. https://doi.org/10.1016/j.anbehav.2011.01.033

Lehtonen, J., Parker, G. A., & Schärer, L. (2016). Why anisogamy drives ancestral sex roles. Evolution, 70(5), 1129–1135. https://doi.org/10.1111/evo.12926

MacFarlane, G. R., Blomberg, S. P., & Vasey, P. L. (2010). Homosexual behaviour in birds: Frequency of expression is related to parental care disparity between the sexes. Animal Behaviour, 80(3), 375–390. https://doi.org/10.1016/j.anbehav.2010.05.009

Rosenthal, G. G. (2017). Mate choice. The evolution of sexual decision making from microbes to humans. Princeton, New Jersey: Princeton University Press.

Scharf, I., & Martin, O. Y. (2013). Same-sex sexual behavior in insects and arachnids: Prevalence, causes, and consequences. Behavioral Ecology and Sociobiology, 67(11), 1719–1730. https://doi.org/10.1007/s00265-013-1610-x

Shansky, R. M. (2019). Are hormones a “female problem” for animal research? Science, 364(6443), 825–826. https://doi.org/10.1126/science.aaw7570

Snyder, B. F., & Gowaty, P. A. (2007). A reappraisal of Bateman’s classic study of intrasexual selection. Evolution, 61(11), 2457–2468. https://doi.org/10.1111/j.1558-5646.2007.00212.x

Tang-Martinez, Z. (2005). The Problem with Paradigms: Bateman’s Worldview as a Case Study. Integrative and Comparative Biology, 45(5), 821–830. https://doi.org/10.1093/icb/45.5.821

Trivers, R. L. (1972). Parental investment and sexual selection. In B. Campbell (Ed.), Sexual selection and the Descent of Man, 1871-1971 (pp. 136–179). Chicago: Aldine.

Zuk, M., Garcia-Gonzalez, F., Herberstein, M. E., & Simmons, L. W. (2014). Model Systems, Taxonomic Bias, and Sexual Selection: Beyond Drosophila. Annual Review of Entomology, 59(1), 321–338. https://doi.org/10.1146/annurev-ento-011613-162014



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