The animal's placenta is packed with proteins called growth factors which stimulate the production of cells that make up hair follicles — bulb‑like roots in the skin hairs grow from.

Male pregnancy evolved in these species to increase reproductive success. By shifting gestation to males, females can produce ...

So what is an animal anyway? In our inaugural episode of Crash Course Zoology, we’ll endeavor to answer just that because as it turns out, it’s complicated! But before we get there we’ll ...

at around the time that the animals of the Messel Pit were alive, the mammal placenta was changing. Natural selection was ...