A tropical shrub called Chrysobalanus icaco pushes up through Brazil's white sandy beaches. The plant's leathery oval leaves and tough silver bark give it the distinct appearance of a mangrove species, adapted to a life buffeted by saltwater. Strangely, though, C. icaco also turns up more than a thousand miles inland, in the forests of the western Amazon. "We find fossil mangroves and associated coastal plants in the middle of the Amazon," says paleoecologist Carina Hoorn, at the University of Amsterdam in The Netherlands. The shrub's appearance inland with an assemblage of mangrove plants, noted in a 2019 article, is among the latest lines of evidence hinting that the Caribbean Sea flooded into the western Amazon during the Miocene, sometime in the last 10 to 20 million years (1). If it did, the region could have been awash in shallow saltwater for hundreds of thousands of years after the New evidence, including geophysical modeling, supports the contentious notion that the Caribbean flooded into the western Amazon during the Miocene.