For me, evolution is a given. I see the evidence for evolution all around – in plants and birds and domestic animals; in life-threatening diseases and the limited ways in which we treat them. But I have also believed that Homo sapiens had probably stopped evolving: we have developed the ability to change our environment rather than be changed by it.
Dye too accepted evolution – the change in species through heritable adaptation in response to natural selection – as a given: he gave lots of examples and observations to support Darwin’s theory. But he also gave lots of evidence to prove my supposition that man had stopped evolving was wrong.
I wasn’t alone in my belief. Dye quoted Stephen Jay Gould, who believed there had been no biological change in humans in 40,000 years, and Steve Jones, who reckoned that with medicine reducing deaths before reproductive age and the modern reduction in human fertility – both necessary for differential reproduction through which evolving can occur – that humans were outside the process of evolution. (A fascinating corollary is that many of the diseases that plague modern life – those of old age – can never be eradicated through evolution: by the time they are active, humans have stopped reproducing: resistance to most cancers or Alzheimer’s disease can convey no reproductive advantage.)
In a fascinating discourse, Dye presented much evidence indicating the contrary: that in much of the world, the death rates of children and the evidence of differential reproduction demonstrate that indeed the survival of the fitter – natural selection – is still active: worldwide, ten million children die before the age of five years every year (often from illness which it is in our power to stop); it is just that most evolutionary scientists are in the privileged position of working in developed nations, where childhood mortality is greatly reduced and fertility is generally below or at the replacement rate. Similarly, some individuals in the developing world produce many more children than others.
But it is not entirely a process limited to the developing world. Different parts of England have significantly different childhood mortality rates, which have been stable in terms of the relative pattern since the 1860s.
Dye presented much data to support his view that there had been extensive selection pressure in the last 80,000 years – and that the rate of change – the rate of evolution – had increased in the last 40,000 years, and particularly in the last 10,000 years: modern man is still evolving, probably as a result of increased population growth in recent times.
I was going to go into a lot more detail, but you can read Dye’s lecture notes for yourself: I would just be regurgitating his thoughts. (You can also read some of what he said in the Independent; but they seem to have posted only some of his lecture, and messed that up, too.) But he definitely convinced me that man is still evolving.
Instead, I want to say what an excellent institution I think Gresham’s is. In the last month, I have been to two events they have organised, and both have been fascinating. They seem to attract an eclectic and interested audience – and a large one, too. I anticipate I shall go frequently to their lectures when I can.