(left to right): THE JOHN CARTER BROWN LIBRARY AT BROWN UNIVERSITY; ROGER HART/UNIVERSITY OF MICHIGAN PHOTOGRAPHY; JULIO LACERDA/STUDIO 252MYA

Top stories: Science and the slave trade, tweeting and (not) flying, and Snowball Earth’s thaw

Historians expose early scientists’ debt to the slave trade

The progressive nature of science has made it hard for historians to take a critical look at its past. But researchers are starting to uncover new connections between science and the slave trade that show just how deeply intertwined they once were. In order to gain access to Africa and the Americas, for example, most early naturalists hitched a ride on a slaving ship. Now, modern scientists and historians are grappling with the horrific origins of some of the world’s most extensive natural history collections.

Tweeting while flying kills migratory birds

Texting while driving can be deadly. So can tweeting while flying, a new study finds—among some species of migratory birds. Researchers have found that birds using faint, high-frequency vocalizations known as flight calls during their nighttime migrations are losing their bearings, crashing into buildings, and possibly luring more birds to their untimely ends.

Ancient ‘Snowball Earth’ thawed out in a flash

More than half a billion years ago, our planet was a giant snowball. Glaciers blanketed the globe all the way to the equator in one of the mysterious “Snowball Earth” events geologists think occurred at least twice in Earth’s ancient past. Now, scientists have found that the final snowball episode likely ended in a flash about 635 million years ago—a geologically fast event that may have implications for today’s human-driven global warming.

Our mysterious cousins—the Denisovans—may have mated with modern humans as recently as 15,000 years ago

The elusive Denisovans, the extinct cousins of Neanderthals, are known from only the scraps of bone they left in Siberia’s Denisova Cave in Russia and the genetic legacy they bequeathed to living people across Asia. A new study of that legacy in people from New Guinea suggests that, far from being a single group, these mysterious humans were so diverse that their populations were as distantly related to each other as they were to Neanderthals. The study also implies that one of those groups may have survived long enough to have encountered modern humans.

Does your cat know its name? Here’s how to find out

For the first time, researchers have experimentally shown that cats have some understanding of what we’re saying to them. Japanese scientists played recordings of different words before playing a recording of a feline’s actual name. The random words evoked no response, but as soon as the cats heard their name, most moved their ears and heads; a few even got up. But whether the cats understand what their name means—and that it’s just not another word for “treat”—remains unclear.