As a result, the very first mammals and dinosaurs evolved.

But eventually mammals evolved to a point where sleep could be modified by changed circumstances.

Certain mammals at this time evolved the ability of allowing their eggs to hatch while still in the body.

It was at this epoch that the "true" mammals evolved.

But the little mammals evolved after that, and we have their bones to prove it.

Researchers are interested in figuring out how mammals evolved such large and complex brains.

The tree allowed researchers to estimate the rate at which mammals have evolved into new lineages.

In this epoch "true" mammals evolved from a group of cynodonts.

Mammals evolved roughly 200 million years ago, either before or during the Early Jurassic period.

Meanwhile, on the Crucible, dinosaurs and mammals had long been evolving alongside one another.