In a scientific first, researchers captured lice attempting to have sex on camera. The research was part of a new University of Utah experiment designed to show how natural selection can cause new species to form. “No one has filmed lice mating before, I guarantee you that,” Scott Villa, one of the biologists, said in a press release.

The biologists split a selection of parasitic feather lice into two groups, and placed them onto two different pigeons—one large, one small. Sixty generations of lice later, the scientists had two groups of lice—one oversized and one undersized.

This evolutionary development led to the male lice’s failure to perform: They physically could not mate with the females, who now dwarfed them in size. It was evidence of “ecological speciation,” a theory Charles Darwin once championed, which stated that different populations within a species will adapt to their environments, and sometimes those adaptations will lead to the creation of an entirely new species.