Everything that lives will die. That's the fundamental fact of life. But not everyone dies at the same age: people vary wildly in their patterns of aging and their life spans – and that variation is nothing compared to what's found in other animal an...

The landscape of southwestern Wyoming around the ghost town of Fossil is beautiful but harsh; a dry, high mountain desert with cool nights and long, cold winters inhabited by a sparse mountain desert community. But during the early Eocene, more than...