Continuous traits: Breaking Down the Binaries

Essential Question: How should humans be grouped into categories?

Standards:

• LS3B: Variation of Traits

• Patterns (CCC)

A common way to start a genetics unit is to ask students to classify some of their own Mendelian traits. Ask students whether they have a widow’s peak, attached earlobes, and hitchhiker’s thumb, but then throw in some more challenging ones. Are they tall or short? Do they have dark skin or light skin? Lead into a discussion about how it felt to partake in the activity. Some traits might have been hard to categorize because they are influenced by the environment, are polygenic, or are hard to measure objectively. Use a data-based activity to introduce the idea of between-group and within-group difference, an important genetic idea that applies to speciation, biodiversity, and countless other topics. Discuss how science can (or should) influence how we categorize people and why we place them in categories in the first place. Why is it important to collect information about race and ethnicity on the census? Is sexuality fixed or fluid? How is our understanding of gender changing to reflect a spectrum rather than a binary? 

Image: Gabriel Liguori