HOW LIVES BECOME LONG

It is easy to feel sorry for the gastrotrich. This invertebrate animal, the size of a poppy seed and the shape of a bowling pin, swarms by the millions in rivers and lakes. After it hatches, it takes only three days to develop a complicated body, complete with a mouth, a gut, sensory organs, and a brain. Having reached maturity in just seventy-two hours, the gastrotrich starts laying eggs. And after a few more days, it becomes enfeebled and dies of old age.

To squeeze a whole life into a week seems like one of nature’s more cruel tricks. But that’s only because we are accustomed to measure our lives in decades. If the ancient animals and plants