Sex can be classified in many ways depending on the species and context. The one fundamental method of classification that applies to all living things is to look at the size of the gametes. This article summarizes the concept of anisogamy (having two gametes of different size) and its evolutionary origins.
Other, Neither, Both - Talk by Sam Sharpe
Biological sex takes on so many diverse patterns across species, but discussion of human sex often consists of an oversimplified and incomplete binary. Biologist Sam Sharpe discussed this issue in a five-minute INSPIRE talk at the Ecological Society of America annual meeting in 2020.
The Unbelievable Secrets of Sex-Changing Animals
In Interesting Engineering, Trevor English surveys the common phenomenon of animals changing sex, and its physiological and genetic basis. For student-facing use, we recommend prefacing this article with a language distinction: Animals “change sex” meaning there is a change in their production of sex hormones and a physical change in their reproductive organs. Humans instead undergo “gender transition”, with “sex change” being an outdated term for this process.
Are There “Transgender” Proclivities in Animals?
In JSTOR Daily, Juliet Lamb discusses non-human species that gain advantages by project an opposite-sex appearance which has parallels to transgender humans.
Why does Homosexuality Evolve?
This video by Soliloquy outlines several hypotheses for why same-sex sexual behavior has persisted rather than becoming extinct in human and nonhuman species. Although not all of these hypotheses are supported by data, the video demonstrates how a behavior that appears deleterious to an individual can actually be neutral or beneficial when considering the complex social interactions within a population.
The Evolutionary Puzzle of Homosexuality
In BBC News, William Kremer discusses how homosexuality in humans and animal species may fit in with the theory of evolution.
The Evolutionary Mystery of Homosexuality
In The Chronicle of Higher Education, evolutionary biologist David P. Barash reviews six leading hypotheses for the evolution of homosexuality as a behavior.
Teaching the Biology of Gender, Sex, and Sexuality Leads to a Marked Increase in Acceptance of the Theory of Evolution by Natural Selection
This research by Nathan H. Lents finds that undergraduate students are more likely to accept evolutionary concepts after learning about the biological basis of reproduction and sexuality. The authors suggest that the topics of reproduction and sexuality may be opening students’ minds to accepting the ideas of evolution, or that these topics are high-interest and they make tangible and striking examples of evolution.