Why Limit Life Span?
Why, then, do animals have a gene such as daf-2, whose apparent purpose (when not mutated) is to limit life span? Try considering that question from a different point of view. The daf-2 gene seems to be just one cog in an extended genetic system that allows worms to regulate their development according to their circumstance. Thanks to this system, those aspects of growth and development that are necessary for reproduction can be put on hold if environmental conditions are poor. Indeed, growing worms are actually able to suspend their own development in a phase known as dauer. This allows them to wait—for months, if need be—for better times. Long before Kenyon’s work, other researchers linked daf-2 and daf-16 to this arrested form of development. In fact, the genes’ names derive from the phrase “dauer formation.” Moreover, experimentally “knocking out” the activity of daf-2 sends a developing worm right into the dauer state, whether or not nutrients are scarce. But is this sort of insul
