Tuesday, 7 October 2008

Human evolution has slowed down, says Steve Jones

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In a lecture to be delivered tonight at UCL, the geneticist Steve Jones (who contributed to our "Dinner with Darwin" feature earlier this year) will say that modern human population and reproductive patterns mean the evolution of our species has slowed dramatically.

The lecture is entitled "Human evolution is over", and this is how the media have been framing Jones' findings, although he's not quite saying that the process has stopped completely. Rather, he says that several factors have led to a slow-down, most strikingly the huge fall in the number of fathers over the age of 50, particularly in Western societies:
“Every time there is a cell division, there is a chance of a mistake, a mutation, an error. For a 29-year old father [the mean age of reproduction in the West] there are around 300 divisions between the sperm that made him and the one he passes on – each one with an opportunity to make mistakes. For a 50-year-old father, the figure is well over a thousand. A drop in the number of older fathers will thus have a major effect on the rate of mutation.”
Other factors are the increased life expectancy of humans, which has lowered the capacity for natural selection, and the sheer size of the human population:
"Humans are 10,000 times more common than we should be, according to the rules of the animal kingdom, and we have agriculture to thank for that. Without farming, the world population would probably have reached half a million by now – about the size of the population of Glasgow. Small populations which are isolated can evolve at random as genes are accidentally lost. World-wide, all populations are becoming connected and the opportunity for random change is dwindling. History is made in bed, but nowadays the beds are getting closer together. We are mixing into a global mass, and the future is brown."
You can listen to a recording of Jones discussing this on the Today programme this morning.

3 comments:

Fred Garnett said...

Hi, I am a fan of Steve Jones work and a great admirer of his public anti-creationism position. He is very consistent and thoughtful scientist. However this view, which I see he has been expounding for several years, reminds me most of Francis Fukuyama's triumphalist End of History position - which Richard Sennett neatly took apart in The Craftsman recently. Steve Jones seems to be arguing that from the perspective his intellectual tools offers him evolution is at an end. Perhaps he needs to broaden his frame of reference; it would be a pity to have his voice devalued in our fundamentalist times.

FSMichael said...

I don't think he is claiming evolution is stopping, merely slowing down. Evolution can't come to a halt unless there is a constant environment, in which case there is no need to adapt. I do believe it is possible that human evolution has slowed down, though. Many factors can cause this, but at the same time there are factors that can speed up evolution, such as our large brains...

Janet said...

Perfect cartoon for this: Red state science