What happened 50-40 millions years ago?

Answer 1

In Canada and Scotland, not much. It was the middle of the most recent ice age and both those areas were covered in thick ice even in winter: no trees, no grass, no people. The tropics were more interesting.

Answer 2

It was the middle of the Paleogene, the period that followed the Cretaceous. The world grew warmer, and there were forests all the way to the poles. The animal life became smaller, probably because small animals have relatively more surface area and are better able to shed body heat. The dinosaurs were of course all gone by then and mammals began to diversify, developing many of the features seen today.