This activity explores the content and research presented in the short film The Making of the Fittest: Evolving Switches, Evolving Bodies, which illustrates how mutations in gene regulatory regions can play a role in the evolution of major anatomical features.

Many freshwater populations of stickleback fish lack the long spines that project from the pelvis of their marine relatives. These spines are important in the ocean for fending off large predators, so why were they lost in freshwater populations? The film tells the story of how David Kingsley, Michael Bell, and other scientists have identified key genes and genetic switches responsible for the evolution of this remarkable body transformation. Scientists have even documented similar evolutionary changes that occurred in the past, by studying a remarkable fossil record from the site of what was an ancient lake ten million years ago.

The “Student Handout” probes students’ understanding of the key concepts addressed in the film. The “Educator Materials” document provides suggested pause points in the film with questions for students, background information, and detailed discussion points; a list of related resources and references; and an answer key for the “Student Handout.”