Difference Between Humans and Animals, Part XXIV

First, the surprising similarity of all animals:

Though big and little creatures look very different, below the surface there is a surprising unity. Biologists have compared the heartbeats of mammals and discovered that on average (this won't apply to any individual, just to groups) elephants and shrews and most of the critters in between have a limit of about a billion and a half heartbeats in a lifetime and then they die.

That is, except for us:

Human beings used to fit into this pattern, but now that we have learned to drink safe water, wash and bathe and create medicines, we last longer than our size would predict.

You can hear the details at NPR's Krulwich Wonders.