Time available for evolution?

I am a retired physicist and was fortunate to find a copy of “Faith of a Physicist” while searching the shelves of a bookstore some years ago. It was my introduction to Dr. Polkinghorne’s work – I have since read several more – and I find his use of a “bottom up” approach attractive; it helps me in the struggle to rationalize my Christian faith. I have a rather simplistic question of a practical nature. In common with most scientists I believe the evidence for evolution is overwhelming.

My problem is with the time available for the development of the world, as we see it today, from the initial single celled organism that was created. An important link in human evolution appears to be “Lucy”, alive about 3 million years ago. She is thought to have been a close relative of homo sapiens, exhibiting bi-pedalism, and yet it took 3 million years for the relatively small changes necessary for her evolution into what we know today as humans. If we take those 3 million years and divide it into the full life of the earth of 4.5 billion years we arrive at the number 1500. So there has only been time, even in the full life of the earth, for 1500 evolutionary “Lucy” steps to have taken place to get us from a single celled organism to the complexity we see now. The number of steps is surely too few to achieve this; even if evolution were 10 or 100 times more rapid, the steps available would still be insufficient. How are we to resolve this dilemma? Does this mean that God has had a more active role in evolutionary development than we think?

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This is an interesting point.

The timescales in evolutionary development are complex and ill-understood: my friend and collaborator Martin Nowak is a pioneer of the field of Evolutionary Dynamics, but it’s a rapidly evolving field. However the natural unit of evolutionary time is generations rather than years: there may be roughly only 15,000 human generations since “Lucy” but millions of ant-generations and billions of bacteria-generations.

Nevertheless it appears that it took about 1.8bn of the 3.5bn years since the origin of life on earth for even multi-cellular organisms to form, and another c1.2bn years for vertebrates. Much remains to be understood!