Placental mammals -- the evolutionary lineage that includes humans -- co-existed with non-avian dinosaurs for a short time before the dinosaurs went extinct, according to new research.
Placental mammals — the evolutionary lineage that includes humans — co-existed with non-avian dinosaurs for a short time before the dinosaurs went extinct, according to new research. About 66 million years ago, a massive asteroid crashed into Earth near the site of the small town of Chicxulub in what is now Mexico. This impact unleashed an incredible amount of climate-changing gases into the atmosphere, triggering a chain of events that led to the extinction of non-avian dinosaurs and 75% of life on the planet. Debate has long raged among paleontologists over whether placental mammals were present alongside the dinosaurs before the end-Cretaceous mass extinction, or whether they only evolved after the dinosaurs were done away with. Fossils of placental mammals are only found in rocks younger than 66 million years old, suggesting that the group evolved after the mass extinction. However, molecular data has long suggested an older age for placental mammals. In the new study, University…