0 from or referring to the period of time between about 22 and 2.5 million years ago, in which many modern mammals and the earliest forms of humans appeared:
1 the period of time between about 22 and 2.5 million years ago, in which many modern mammals and the earliest forms of humans appeared:
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.