Richard Dawkins, at the end of this video illustrates the span of geological time by holding out his arm.
He explains: if the whole of time from the development of the first life form (primitive bacteria) were his tie, multi-cellular creatures developed around his wrist, dinosaurs (65 million years ago) in his palm, and mankind would be at his fingertips.
The whole of recorded human history would be the dust created by a single stroke from a nail-file on his fingernail.
This timeline, to me at least, indicates that the rate of evolutionary change (simple becoming more complex) is accelerating. It is taking less and less time for organisms to become more complex.
Why is that? And does that mean that we are aproaching a time when the time-frame for evolutionary change will be observable in a human lifetime?