Reconstructing Lost Worlds With Poop

Forty years ago, the great tropical ecologist Dan Janzen noticed something funny about the plants in Costa Rica. Many species invested a lot of their energy in producing huge fruits with tough seeds and seed pods, which no animals seemed to eat. With nothing to consume them, the seeds and pods just fell to the jungle floor and rotted, or died in the shade of their parent trees.

In a now legendary cowritten with Paul S. Martin (“Neotropical Anachronisms: The Fruits the Gomphotheres Ate”), Janzen speculated that there was a good reason for this: The jungle plants’ original partners had all gone extinct. They identified a long list of plants, such as the jicaro and guanacaste in South America and honey locust, pawpaw, persimmon, and Osage orange in North America, which seem to have lost their original dispersal agents. These species had evolved over millions of years to have their seeds eaten and spread around by ground sloths, glyptodonts, gomphotheres, (a family of mastodon-like creatures from South America), extinct horses, and other