Speciation as a prisoner’s dilemma

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This by Freeman Dyson was pretty cool. Not the stuff about how open-source biotechnology is going to change the world–maybe he’s right, maybe he’s wrong, but it comes across to me as generic science writing. The cool stuff was his discussion of the ideas of Carl Woese (whom I’d never previously heard of):

[Woese asks] When did Darwinian evolution begin? By Darwinian evolution he means evolution as Darwin understood it, based on the competition for survival of noninterbreeding species. He presents evidence that Darwinian evolution does not go back to the beginning of life. When we compare genomes of ancient lineages of living creatures, we find evidence of numerous transfers of genetic information from one lineage to another. In early times, horizontal gene transfer, the sharing of genes between unrelated species, was prevalent. It becomes more prevalent the further back you go in time. . . .

In his “New Biology” article, he is postulating a golden age of pre-Darwinian life, when horizontal gene transfer was universal and separate species did not yet exist. Life was then a community of cells of various kinds, sharing their genetic information so that clever chemical tricks and catalytic processes invented by one creature could be inherited by all of them. Evolution was a communal affair, the whole community advancing in metabolic and reproductive efficiency as the genes of the most efficient cells were shared. Evolution could be rapid, as new chemical devices could be evolved simultaneously by cells of different kinds working in parallel and then reassembled in a single cell by horizontal gene transfer.

But then, one evil day, a cell resembling a primitive bacterium happened to find itself one jump ahead of its neighbors in efficiency. That cell, anticipating Bill Gates by three billion years, separated itself from the community and refused to share. Its offspring became the first species of bacteria—and the first species of any kind—reserving their intellectual property for their own private use. With their superior efficiency, the bacteria continued to prosper and to evolve separately, while the rest of the community continued its communal life. Some millions of years later . . . nothing was left of the community and all life was divided into species. The Darwinian interlude had begun.

Now this is cool–the idea that speciation itself is a sort of prisoner’s dilemma, or killer app, so that once a species is formed, it can preserve its genetic identity and eventually outlast the faster-evolving but less walled-off organisms around them. Speciation has always been a mystifying aspect of evolution to me, so it’s interesting to see this (possibly false, but interesting) theory.

6 thoughts on “Speciation as a prisoner’s dilemma”

  1. I've heard Darwinian evolution defined as evolution by natural selection. I've heard Darwninian evolution defined as common descent. But I've never seen the two conflated in such a manner as done here. Natural selection is competition between individuals of the same species. Shared ancestry between different species is common descent. The quote above is just an absolute mess.

    And the concept of speciation is pretty shakey when it comes to asexually reproducing lineages.

  2. As far as I understand Richard Dawkins it is not the individual organism that is being "naturally selected" but rather the individual gene (gene selection). I guess horizontal gene transfer would still include gene selection? Maybe I got it wrong?

  3. I remember reading one or two years ago that non-darwinian evolution occurs even today. It was in a article that mentioned a dozen methods of non-darwinian evolution. Several purported to help explain the swift spread of drug resistance seen in bacteria.

  4. Ah, this happened even before bacteria. At some point, a group of molecules decided to build a wall around themselves and stop mixing with other molecules: the interaction with the rest of the molecular collective was then restricted to ingestion and excretion.

  5. Nowak's Evolutionary Dynamics has a couple good chapers on evolutionary game theory. Also, see this article in the NYT

    Myxococcus swarms lash their tails together and hunt in a pack, releasing enzymes to kill their prey and feasting on the remains. If the bacteria starve, they come together to form a mound of spores. It is a cooperative effort. Only a few percent of the bacteria end up forming spores, while the rest face almost certain death.

    This social behavior costs Myxococcus energy that it could otherwise use to grow, Dr. Velicer discovered. He and his colleagues allowed the bacteria to evolve for 1,000 generations in a rich broth. Most of the lines of bacteria lost the ability to swarm or form spores, or both.

    Dr. Velicer discovered that some of the newly evolved bacteria were not just asocial — they were positively antisocial.
    …
    During this experiment, one of Dr. Velicer’s colleagues, Francesca Fiegna of the Max Planck Institute for Developmental Biology, discovered something strange. She had just transferred a population of cheaters to a dish, expecting them to die out. But the cheaters were making seven times as many spores as their normal ancestors. “It just made no sense,” Dr. Velicer said. “I asked her I don’t know how many times, ‘Are you sure you marked the plates correctly?’ ”

    She had. It turned out that a single Myxococcus cheater had mutated into a cooperator. In fact, it had evolved into a cooperator far superior to its cooperative ancestors.

  6. As far as I understand Richard Dawkins it is not the individual organism that is being "naturally selected" but rather the individual gene (gene selection). I guess horizontal gene transfer would still include gene selection? Maybe I got it wrong?

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