The earliest mammals might have been cold-blooded Magdalena Rehova / Alamy Stock Photo
Our mammal ancestors were cold-blooded for tens of millions of years after their first appearance. In this respect, the early mammals remained similar to the cold-blooded reptiles from which they evolved.
The finding comes from an analysis of fossils of two early mammal species, which suggests the animals lived relatively long lives and had slow metabolisms – both reptile-like traits.
Mammals are animals that have hair and make milk. The first mammals evolved during the dinosaur era. The oldest known mammal-like animals, like Tikitherium, lived about 230…
