Evolution accelerates. History shows that next steps in life development take less and less time to happen.
It took about 3B years to evolve from simple life-forms to multicellular organisms. Craniates appeared few hundred million years ago, mammals ten million years ago and so on.
We, as species, emerged some hundred thousand years ago. Civilization started a few thousand years ago.
The reason for this shortening of the evolution time spans is probably the fact that each sequential step is based and uses the development of all previous steps. It is easy to evolve, once you have done the hard part - start the life and sustain it for a long period of time.
This pattern of shortening the time of development is most likely to continue, unless something disruptive happens, like nuclear war, global warming (already happening), or the Moon decides to leave us (which, in fact, is also happening). Each new development requires a fraction of the time required for the previous one. More...