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.
Yvette Roubideaux decided she wanted to become a physician when she was 16. A member of the Rosebud Sioux Tribe in South Dakota, she had seen the delays and staff shortages at health facilities on the reservation as she was growing up. She felt there was a need for more American Indian doctors to help improve the situation.