Kay Frydenborg introduces her middle-grade book, Wild Horse Scientists, about the horses of Assateague Island and the people who study and work with them.

The 2.8 million-year-old mandible and teeth push back the origin of the human genus by nearly half a million years.

A tiny, furry-tailed creature was the earliest ancestor of the placental mammals—a group excluding marsupials and egg-laying mammals—and lived after the extinction of the dinosaurs, according to a study in the 8 February Science.

The origins and early evolution of placental mammals have long been a matter of debate.