"When families of green plants and insects began living on the land, we followed them.
On the outside, we still had scales, but we looked like huge salamanders. We crawled out of the sea on legs, two on each side. We didn't stray far, and we returned to the water to lay our eggs. On the inside, we had lungs to breathe oxygen, like we do now.
As all of the continents on earth slowly joined into one, we left the water completely.
On the outside, we looked like hairy lizards. We hunted all day and had sharp teeth to tear our food. On the inside, our blood ran warm, almost as warm as it does today.
In one of the earth's darkest times, nearly all life went extinct, but many families survived. Ours was among them.
On the outside, we were small and furry. We hid or slept during the day, and we scurried about at night. On the inside, we made milk for our babies, the way we do now."