More than two thousand years ago, Greek philosopher Aristotle observed that larger animals tend to live longer than smaller ones. On June 18 in the journal Developmental Cell, scientists report that it’s cell size, not body size, that intrinsically correlates with and perhaps affects lifespan. By examining the pancreases of 24 mammalian species—including shrews, humans, and tigers—researchers in Israel, Canada, and Germany found that animals with larger pancreatic cells tend to age faster, while smaller cells seem to go hand in hand with longer lifespans.