Evolution, yes. Natural selection, not so much?

Last time, we looked at Timothy D. Wilson’s argument that evolutionary social psychologists have overstepped their evidence, claiming more of the territory of human behaviour than is their due. A while ago, we dissected Raymond Tallis’s similar criticism of cognitive psychology,  Aping Mankind. 

Now, Lynn Margulis, a noted veteran of the microbiology wars, has reemerged with guns blazing in a new interview on the edge.org. website, repeating her familiar claim that speciation comes from symbiosis, not natural selection.

Although by now it should go without saying, it doesn’t, so here it goes again: These writers all accept the fact of evolution. Period. End of story. Sorry, ID advocates. You can continue to misrepresent all you like, but they’re all evolutionists.

The bone they have to pick with their “neo-Darwinist” colleagues is over the extent to which natural selection explains the mechanisms of evolution. For Tallis, selection alone doesn’t explain the human “self”; for Wilson, selection alone doesn’t explain social behaviour. And for Margulis, who says that “natural selection eliminates and maybe maintains, but it doesn’t create,” natural selection is not the source of speciation:

All scientists agree that evolution has occurred—that all life comes from a common ancestry, that there has been extinction, and that new taxa, new biological groups, have arisen. The question is, is natural selection enough to explain evolution? Is it the driver of evolution?

Simpy put, Margulis answers “no.” For her, evolution is driven not by natural selection but by symbiogenesis. One short summary of the process of symbiogenesis can be found in a recent study in evolutionary computation (a mathematical subfield of biology):

When the symbiotic association leads to a long-term relationship that, say, converts an initially exploitive relationship into one of co-operative dependence resulting in a new species then the process is considered to be that of symbiogenesis. The core components include: (1) partners entering in a relationship from different species/ organisms; (2) partners adapting phenotypically under selection pressure as a result of the symbiotic relationship, and; (3) a long term association which facilitates the creation of a new species of organism(s). The first two points are sufficient for symbiosis, whereas all three points provide symbiogenesis.

Margulis claims that “there is no gradualism in the fossil record.” Suddenly, about 550 million years ago, most major types of organisms just “appeared.” Margulis argues that while natural selection can’t explain this sudden genesis, symbiosis can. Rather than species being produced through competitive selection, in her view the differentiation of species occurred primarily through cooperation, through the merging of separate organisms into new and more complex creatures which exist because their component parts have learned to live together.

Margulis concedes that natural selection is the cause of relatively small variations between different species of similar animals — differences in the beak sizes of Galapagos finches is a familiar example. However, she argues that selection does not account for major changes.

Margulis reiterates that the perceived inadequacy of selection to explain evolution is not an argument against evolution itself:

The critics, including the creationist critics, are right about their criticism. It’s just that they’ve got nothing to offer but intelligent design or “God did it.” They have no alternatives that are scientific.

Indeed, when ID advocates like Michael Behe claim that Margulis’s conflict with those who support natural selection shows that “the science isn’t settled,” they’re making as nonsensical an argument as would be the claim that automobiles don’t exist because you think that red car is a Buick and I think it’s a Ford.

Yet Margulis’s criticism of the neo-Darwinists continues to bounce around the religious and ID websites. In a short search, I encountered dozens of sites which twisted and turned her words in all kinds of creative (what else?) ways to make it look like evolution itself was in dispute.

One constant blogger who’s having none of it is Jerry Coyne, whose excellent book Why Evolution is True was reviewed here recently. His assessment of Margulis’s claim for symbiogenesis is expressed in his usual gentle style:

But where on earth does Margulis get the idea that artificial selection shows that “natural selection doesn’t create”?  Artificial selection, of course, does create, in that, as Darwin famously noted, humans can mold animals or plants into pretty much anything they like. This shows that combining different mutations can make something new: it can turn an ancestral plant into either a cauliflower, a kohlrabi, a Brussels sprout, or a cabbage (all derived from the same species).  And if those changes increased fitness in nature, as for example the combination of traits that turned an ancestral artiodactyl into a whale, why wouldn’t natural selection create something new?  The fossil record for the evolution of major taxa attests to this completely—unless Margulis thinks that flippers, feathers, and the like all arose by symbiosis or hybridization.  I suspect that she does, which would be a ludicrous and unsupported point of view.

Margulis is undaunted by this kind of reaction.  At the end of the edge interview, she says, “
I don’t consider my ideas controversial. I consider them right.”


2 thoughts on “Evolution, yes. Natural selection, not so much?

  1. Margulis puts the arguments back where they belong: based on evidence and reasoned conclusions, not wasting too much energy in being defensive.

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