By Abby Weber, PhD Student, Department of Evolution, Ecology, & Behavior, at the Anderson Evolutionary Biomechanics Lab of the University of Illinois Urbana-Champaign
Can sexual diversity be accurately captured by a male-female binary? Sara Lipshutz of Loyola University Chicago explored alternative models of animal sex in her talk “Multimodal models of animal sex: breaking binaries to better understand reproductive behaviors” at SICB 2023 as part of the Sexual Variation and Diversity symposium. Her co authors on this paper are J.F. McLaughlin, Kinsey M. Brock, Isabella Gates, Anisha Pethkar, Marcus Piattoni, and Alexi Rossi. Graphics in this blog were also created by J.F. McLaughlin!
Dr. Lipshutz’s talk advocated that biological sex is a construct that operates at multiple biological levels, meaning sexual diversity cannot be accurately captured by a male-female binary. Variation in gametes, genetics, anatomy, behavior, hormones, and brains are some of the characteristics she argues should be included when categorizing sexual differences in organisms. The graphic below demonstrates the diversity of gametic sex in the animal kingdom! Not every animal fits within an XX female XY male binary.
A compelling example of an organism that does not fit into a male-female binary model is the Northern Jacana. Northern Jacanas phenotypically present in ways anatomically, behaviorally, and hormonally that are difficult to classify into two sex categories. ZW sex chromosome females can exist in two phenotypes, breeder or floater. Breeder females have large follicles and lay eggs daily, while floaters have small follicles and do not lay eggs. A massive contradiction to the traditional sex roles of the binary system is that female-female competition largely drives mating success in Northern Jacanas. Females mate with many males and males do 100% of parental care. Another example that falls outside of this binary is that ZZ sex chromosome males doing parental care have similar hormone levels to the breeding ZW females.
In this case, we still refer to them as female and male for ease of identification, but it is important to acknowledge the diversity present within and between gametic sexes. Attempting to fit these birds into a sex binary fails to capture the complexity of their sex characteristics. Jacanas are just one example of many that we can use to shift our way of thinking. Dr. Lipshutz suggests that instead of trying to fit organisms into two boxes we instead ask the following two questions: “What specifically are the sexual phenotypes?” and “Are these phenotypes discrete or continuous?” The graphic below demonstrates different models of sex characteristics: A) bimodal discrete, B) bimodal continuous, C) multimodal continuous, the model Dr. Lipshutz and colleagues are in favor of.
Dr. Lipshutz expressed that biologists must start using specific language when discussing sexual variation instead of defaulting to binaries that we as a society have an internalized bias toward. She argues that simplifying to teaching sex binaries in the classroom doesn’t prepare students to understand sexual diversity. Another point she raises is that if biologists perpetuate this binary thinking, then society might misconstrue our work to perpetuate and justify discrimination toward people who exist outside of sex binaries.
I had the opportunity to chat with Dr. Lipshutz about this topic a little further:
Abby: What would you suggest to young biologists that want to start addressing how their biases might shape their work?
Dr. Lipshutz: “First ask yourself what your biases might be. When I started my graduate studies, I thought there was some objective point that I could reach where I would just know all the facts. Over time, I realized there is no objectivity in science. The field I work in, genetics, has a really harmful past that is full of bias. I’d say start off by recognizing there is no such thing as objectivity in your work.”
Abby: How do you think shifting to a multimodal model of describing sex variation in non-human research will affect the way we view sex and gender in humans?
Dr. Lipshutz: “I actually came at this article from a political place, which is scary because I’m supposed to be the objective and neutral scientist. I was really upset at some of these policies aimed at harming transgender people. A lot of people try to justify this hate with science. I felt like not enough scientists were speaking out. This article is a letter to other biologists about how we might expand our framework of sex, including what paradigms we uphold and for whose benefit. I’d also like to acknowledge Hans Lindahl and Alicia Weigel, who also spoke at the symposium. We need to hear more about the perspectives of intersex people!”
Connect with Dr. Lipshutz via:
Read Dr .Lipshutz’s previous ICB work:
Neuroendocrinology of Sex-Role Reversal
Sara E Lipshutz, Kimberly A Rosvall
Integrative and Comparative Biology, Volume 60, Issue 3, September 2020, Pages 692–702, https://doi.org/10.1093/icb/icaa046
Connect with writer, Abby Weber