Letter to The New York Times
by Frank P. Ryan

Re: Mark Ridley's review of my book, Darwin's Blind Spot


Mark Ridley protests at my linking Darwinism with eugenics. In fact, in the words of Hawkins¹, "it is both perverse and inaccurate to deny his (Darwin's) status as a social Darwinist." His cousin and close confidante, Galton, co-founded the British Eugenics Society and Darwin's son, Leonard, was one of its presidents. That isn't to say Darwin would have approved of the extreme consequences, such as the eugenic policies of the Nazis. I'm certain he would have been horrified.

Most biologists, Ridley writes, will be surprised to learn that "the majority of Darwinians resist the notion that symbiosis has played an important role in complex life-forms." In this, I am actually quoting the opinion of John Maynard Smith², one of the greatest living Darwinians. In my book I challenge this assumption, redefining symbiosis to take on board modern genetics and genomics and showing how symbiosis - like its societal parallel, cooperation - has played, and is still playing, a vital role in higher life forms, and in particular in human evolution. Ridley goes on to dispute my view that symbiotic evolution is a separate force from natural selection. In his Origin of Species, Charles Darwin acknowledges that natural selection is not the only force in evolution. He is specific in excluding sudden evolutionary change - "saltations" - as incompatible with natural selection. When two different life forms combine their genomes (endosymbiosis), a new life-form emerges in what amounts to the evolutionary equivalent of the blink of an eye. I respect Darwin's opinion that this is indeed evolution beyond natural selection.

Ridley further claims that I merely enumerate examples of symbiosis and fail to discuss its relative importance. On the contrary, I examine its role in the major transitions in evolution, where, for example, it helped to create all five kingdoms of life and many (Margulis believes all) of the major subdivisions, known as phyla. This is not to downplay the fundamental importance of natural selection. I don't, as he claims, see natural selection and symbiosis as rivals. I see them as complementary forces. Symbiotic evolution will inevitably be further adapted by natural selection, working not at the level of individuals but the relationship as a whole (Maynard Smith). It is natural selection that has honed the beak of the hummingbird to fit the flower. But in all such symbioses, natural selection is secondary to the main innovative step, which is the coming together of two or more life-forms, with radically different evolutionary inheritances, to share their behaviors, chemistries or genomes.


1. Hawkins M, 1997. Social Darwinism in European and American Thought. Cambridge Univ Press; 36.

2. Maynard Smith J, 1991. Chapter 3: A Darwinian View of Symbiosis, in Symbiosis as a Source of Evolutionary Innovation, ed. Margulis and Fester; 30.

Hypertext by Terrence Berres
Revised March 13, 2004.

Top