Phylogenetically distant animals sleep: why do sleep researchers care?

Abstract

Philosophers examining mechanistic explanations in biology have identified heuristic strategies scientists use in discovering mechanisms. This paper examines the heuristic strategy of investigating phylogenetically distant model organisms, using research on sleep in fruit flies as an example. At the time sleep was discovered in flies in 2000 next to nothing was known about mechanisms regulating sleep in flies and what they could reveal about those in us. One relatively straightforward line of research focused on homologous genes in flies and humans, using those in flies to understand what roles their homologs played in controlling sleep in us. But other research focused on a higher level of organization—the neural networks involved in homeostatic and circadian control of sleep. This raises a puzzle—given that fly and vertebrate brains are organized very differently, how could sleep regulation in flies serve as an informative model of vertebrate sleep? I argue that the basic design of mechanisms such as those regulating sleep can be conserved even as the composition of the mechanism changes and that researchers can hope to use the designs deciphered in flies as heuristic models for understanding sleep in humans.