RICHARD DAWKINS—FREEMAN DYSON: AN EXCHANGE

As part of this year's Annual Edge Event at Eastover Farm in Bethlehem, CT, I invited three of the participants—Freeman Dyson, George Church, and Craig Venter—to come up a day early, which gave me an opportunity to talk to Dyson about his recent interesting and provocative article in New York Review of Books entitled "Our Biotech Future" in which he had written the following:

"The Darwinian interlude has lasted for two or three billion years. It probably slowed down the pace of evolution considerably. The basic biochemical machinery of life had evolved rapidly during the few hundreds of millions of years of the pre-Darwinian era, and changed very little in the next two billion years of microbial evolution. Darwinian evolution is slow because individual species, once established evolve very little. With rare exceptions, Darwinian evolution requires established species to become extinct so that new species can replace them.

"Now, after three billion years, the Darwinian interlude is over. It was an interlude between two periods of horizontal gene transfer. The epoch of Darwinian evolution based on competition between species ended about ten thousand years ago, when a single species, Homo sapiens, began to dominate and reorganize the biosphere. Since that time, cultural evolution has replaced biological evolution as the main driving force of change. Cultural evolution is not Darwinian. Cultures spread by horizontal transfer of ideas more than by genetic inheritance. Cultural evolution is running a thousand times faster than Darwinian evolution, taking us into a new era of cultural interdependence which we call globalization. And now, as Homo sapiens domesticates the new biotechnology, we are reviving the ancient pre-Darwinian practice of horizontal gene transfer, moving genes easily from microbes to plants and animals, blurring the boundaries between species. We are moving rapidly into the post-Darwinian era, when species other than our own will no longer exist, and the rules of Open Source sharing will be extended from the exchange of software to the exchange of genes. Then the evolution of life will once again be communal, as it was in the good old days before separate species and intellectual property were invented.

I also sent the link to the article to Richard Dawkins, and asked if he would would comment on what Dyson termed the end of "the Darwinian interlude".

Early the next morning, prior to the all-day discussion (which also included as participants Robert Shapiro, Dimitar Sasselov, and Seth Lloyd) Dawkins emailed his thoughts which I read to the group during the discussion following Dyson's talk. [NOTE: Dawkins asked me to make it clear that his email below "was written hastily as a letter to you, and was not designed for publication, or indeed to be read out at a meeting of biologists at your farm!"].

Now Dyson has responded and the exchange is below.

—JB

Link: "Our Biotech Future" By Freeman Dyson (in New York Review of Books, July 17, 2007)

RICHARD DAWKINS [8.27.07]
Evolutionary Biologist, Charles Simonyi Professor For The Understanding Of Science, Oxford University; Author, The God Delusion

"By Darwinian evolution he [Woese] means evolution as Darwin understood it, based on the competition for survival of noninterbreeding species."

"With rare exceptions, Darwinian evolution requires established species to become extinct so that new species can replace them."

These two quotations from Dyson constitute a classic schoolboy howler, a catastrophic misunderstanding of Darwinian evolution. Darwinian evolution, both as Darwin understood it, and as we understand it today in rather different language, is NOT based on the competition for survival of species. It is based on competition for survival WITHIN species. Darwin would have said competition between individuals within every species. I would say competition between genes within gene pools. The difference between those two ways of putting it is small compared with Dyson's howler (shared by most laymen: it is the howler that I wrote The Selfish Gene partly to dispel, and I thought I had pretty much succeeded, but Dyson obviously hasn't read it!) that natural selection is about the differential survival or extinction of species. Of course the extinction of species is extremely important in the history of life, and there may very well be non-random aspects of it (some species are more likely to go extinct than others) but, although this may in some superficial sense resemble Darwinian selection, it is NOT the selection process that has driven evolution. Moreover, arms races between species constitute an important part of the competitive climate that drives Darwinian evolution. But in, for example, the arms race between predators and prey, or parasites and hosts, the competition that drives evolution is all going on within species. Individual foxes don't compete with rabbits, they compete with other individual foxes within their own species to be the ones that catch the rabbits (I would prefer to rephrase it as competition between genes within the fox gene pool).

The rest of Dyson's piece is interesting, as you'd expect, and there really is an interesting sense in which there is an interlude between two periods of horizontal transfer (and we mustn't forget that bacteria still practise horizontal transfer and have done throughout the time when eucaryotes have been in the 'Interlude'). But the interlude in the middle is not the Darwinian Interlude, it is the Meiosis / Sex / Gene-Pool / Species Interlude. Darwinian selection between genes still goes on during eras of horizontal transfer, just as it does during the Interlude. What happened during the 3-billion-year Interlude is that genes were confined to gene pools and limited to competing with other genes within the same species. Previously (and still in bacteria) they were free to compete with other genes more widely (there was no such thing as a species outside the 'Interlude'). If a new period of horizontal transfer is indeed now dawning through technology, genes may become free to compete with other genes more widely yet again.

As I said, there are fascinating ideas in Freeman Dyson's piece. But it is a huge pity it is marred by such an elementary mistake at the heart of it.

Richard

FREEMAN DYSON [8.30.07]
Physicist, Institute of Advanced Study, Author, Many Colored Glass: Reflections on the Place of Life in the Universe

Dear Richard Dawkins,

Thank you for the E-mail that you sent to John Brockman, saying that I had made a "school-boy howler" when I said that Darwinian evolution was a competition between species rather than between individuals. You also said I obviously had not read The Selfish Gene. In fact I did read your book and disagreed with it for the following reasons.

Here are two replies to your E-mail. The first was a verbal response made immediately when Brockman read your E-mail aloud at a meeting of biologists at his farm. The second was written the following day after thinking more carefully about the question.

First response. What I wrote is not a howler and Dawkins is wrong. Species once established evolve very little, and the big steps in evolution mostly occur at speciation events when new species appear with new adaptations. The reason for this is that the rate of evolution of a population is roughly proportional to the inverse square root of the population size. So big steps are most likely when populations are small, giving rise to the ``punctuated equilibrium'' that is seen in the fossil record. The competition is between the new species with a small population adapting fast to new conditions and the old species with a big population adapting slowly.

Second response. It is absurd to think that group selection is less important than individual selection. Consider for example Dodo A and Dodo B, competing for mates and progeny in the dodo population on Mauritius. Dodo A competes much better and
has greater fitness, as measured by individual selection. Dodo A mates more often and has many more grandchildren than Dodo B. A hundred years later, the species is extinct and the fitness of A and B are both reduced to zero. Selection operating at the species level trumps selection at the individual level. Selection at the species level wiped out both A and B because the species neglected to maintain the ability to fly, which was essential to survival when human predators appeared on the island. This situation is not peculiar to dodos. It arises throughout the course of evolution, whenever environmental changes cause species to become extinct.

In my opinion, both these responses are valid, but the second one goes more directly to the issue that divides us. Yours sincerely, Freeman Dyson.