Last Friday, Andrew McDiarmid, our trusted Facebook page administrator, posted a quote on my behalf at my Facebook page from the eminent biologist Lynn Margulis. Margulis, who died in 2011, was a member of the U.S. National Academy of Sciences. She was also known for her outspoken skepticism about neo-Darwinian evolutionary theory — expressed succinctly in the quotation that we posted, which was this:
Natural selection eliminates and maybe maintains, but it doesn’t create … neo-Darwinists say that new species emerge when mutations occur and modify an organism… I believed it until I looked for evidence.
The quote is from an interview with Margulis in Discover Magazine published not long before her death. Our posting this resulted in a lively round of comments, with one commenter protesting that I had misrepresented Margulis. The contention was that I had conflated the words “evolution” and “Darwinism”:
Margulis was an ardent Evolutionist to her death. Here she literally means Darwin, as in the books he wrote over 100 years ago. Meyer often uses Darwinism as a by word for Evolution. He’s hoping you don’t know the difference.
Margulis was the author of endosymbiotic theory which is now the consensus theory of the origin of eukaryotic cells. However Margulis thought it was the main driving force for Evolution, much more than Darwinism (NS) and Neo-Darwinism (Genetic Mutation).
By distinguishing the terms “Darwinism” and “neo-Darwinism,” on the one hand, from evolution, on the other, our Facebook correspondent raised an important issue of definitional clarity. Nevertheless, it is our critics who typically use terminology in an equivocal way, failing to distinguish separate meanings of the same word. In particular, they often use the word “evolution” to mean several different things and fail to recognize that an “evolutionist” might affirm some but not all of the ideas associated with the term evolution. Recall that the term “evolution” can be used in at least three different ways.
- Evolution #1: Change over time — small-scale changes in a population of organisms (often called “microevolution”).
- Evolution #2: Universal common descent — the view that all organisms are related and are descended from a single common ancestor.
- Evolution #3: Natural selection and random mutation as the main cause or mechanism of change during the history of life — the idea that an unguided process of natural selection acting upon random mutations is sufficient to produce the new forms of life that appear during that history as well as the appearance of design that living forms manifest.
Neo-Darwinists affirm all three meanings of the term “evolution” and uniquely affirm the third meaning — the idea of the creative power of the mutation and natural selection mechanism. Sometimes, popularizers have conflated these definitions by treating evidence for small-scale change over time (evolution #1) as if it provided evidence for universal common descent (evolution #2) or the creative power of natural selection and random mutation (evolution #3).
Our Facebook commenter, on the other hand, protested the citation of Margulis as a critic of neo-Darwinism because he thought that I was concealing Margulis’s sympathy for evolution (in some sense) and that I was representing her comments as a critique of modern evolutionary theory when, in his view, they were only directed at Darwin’s version of the theory from 1859.
In fact, both claims are false. Note, first, that Margulis clearly identified “neo-Darwinism,” the modern textbook version of evolutionary theory with its reliance upon natural selection and random mutation (not classical Darwinism), as the object of her critique. As she said, “neo-Darwinists say that new species emerge when mutations occur and modify an organism…I believed it until I looked for evidence” (emphasis added). Secondly, note that in our description of Margulis, we referred to her as an “evolutionary biologist.” In addition, not only did we not make any attempt to conceal Margulis’s sympathies for evolutionary thinking, and thus her support for evolution in the first two senses of the word, but in Darwin’s Doubt I addressed six new (that is, post neo-Darwinian) theories of evolution — theories that proposed new mechanisms to either supplement or replace the reliance upon mutation and natural selection in neo-Darwinian theory. Readers may refer to Chapters 15 and 16 of Darwin’s Doubt. Those chapters reflect ample awareness of the distinction between the different meanings of “evolution” and neo-Darwinian theory, and show that many leading evolutionary theorists agree, as Margulis did, that the natural selection and random mutation mechanism lacks the creative power that neo-Darwinists have long attributed to it.
As noted, many of these contemporary evolutionary theorists have offered alternative mechanisms in an attempt to account for the origin of novel biological form in the history of life. In Darwin’s Doubt, I explain and critique these other theories. Indeed, I show that, although several of these new evolutionary theories offer some intriguing advantages over the orthodox neo-Darwinian model, they too fail to offer adequate explanations for the origin of the genetic and epigenetic information necessary to account for new forms of animal life — such as those that arise in the Cambrian period.
Of course, our friendly critic on Facebook is entirely correct to point out that Professor Margulis herself offered an alternative evolutionary theory, her endosymbiotic hypothesis. Specifically, she promoted endosymbiotic theory as an explanation for the emergence of eukaryotic cells (cells with a nucleus) from prokaryotic cells (cells without a nucleus), proposing that two different one-celled organisms came into a close, integrated, symbiotic relationship with one-another. She believed that eukaryotic mitochondria were once free-living bacteria that were engulfed by other one-celled organisms.
Margulis’s ideas aren’t completely implausible. We can today, for example, observe that corals host different types of algae inside their cells in a symbiotic relationship. The algae helps produce energy for the coral, and the coral provides a safe habitat for the algae, including chemicals upon which the algae feeds. That’s all fine, but endosymbiosis, in the best of cases, can only explain a limited range of biological observations. It certainly does nothing to help explain the origin of animals and animal body plans in the Cambrian period, which is why I didn’t discuss the endosymbiotic hypothesis in Chapter 15 and 16 of Darwin’s Doubt. Nevertheless, endosymbiotic theory has many scientific problems even as an explanation for the origin of eukaryotic cells.
That aside, here are a couple of other quotations from Margulis expressing in more detail her skepticism about neo-Darwinism, and the adequacy of the neo-Darwinian mechanism:
This is the issue I have with neo-Darwinists: They teach that what is generating novelty is the accumulation of random mutations in DNA, in a direction set by natural selection. If you want bigger eggs, you keep selecting the hens that are laying the biggest eggs, and you get bigger and bigger eggs. But you also get hens with defective feathers and wobbly legs. Natural selection eliminates and maybe maintains, but it doesn’t create…. [N]eo-Darwinists say that new species emerge when mutations occur and modify an organism. I was taught over and over again that the accumulation of random mutations led to evolutionary change — led to new species. I believed it until I looked for evidence.Quoted in “Discover Interview: Lynn Margulis Says She’s Not Controversial, She’s Right,” Discover Magazine, p. 68 (April, 2011).
“But many biologists claim they know for sure that random mutation (purposeless chance) is the source of inherited variation that generates new species of life and that life evolved in a single-common-trunk, dichotomously branching-phylogenetic-tree pattern! ‘No!’ I say. Then how did one species evolve into another? This profound research question is assiduously undermined by the hegemony [of those] who flaunt their ‘correct’ solution. Especially dogmatic are those molecular modelers of the ‘tree of life’ who, ignorant of alternative topologies (such as webs), don’t study ancestors. Victims of a Whiteheadian ‘fallacy of misplaced concreteness,’ they correlate computer code with names given by ‘authorities’ to organisms they never see! Our zealous research, ever faithful to the god who dwells in the details, openly challenges such dogmatic certainty. This is science.”Lynn Margulis, “The Phylogenetic Tree Topples,” American Scientist, 94 (3) (May-June, 2006).
“We agree that very few potential offspring ever survive to reproduce and that populations do change through time, and that therefore natural selection is of critical importance to the evolutionary process. But this Darwinian claim to explain all of evolution is a popular half-truth whose lack of explicative power is compensated for only by the religious ferocity of its rhetoric. Although random mutations influenced the course of evolution, their influence was mainly by loss, alteration, and refinement. One mutation confers resistance to malaria but also makes happy blood cells into the deficient oxygen carriers of sickle cell anemics. Another converts a gorgeous newborn into a cystic fibrosis patient or a victim of early onset diabetes. One mutation causes a flighty red-eyed fruit fly to fail to take wing. Never, however, did that one mutation make a wing, a fruit, a woody stem, or a claw appear. Mutations, in summary, tend to induce sickness, death, or deficiencies. No evidence in the vast literature of heredity changes shows unambiguous evidence that random mutation itself, even with geographical isolation of populations, leads to speciation. Then how do new species come into being? How do cauliflowers descend from tiny, wild Mediterranean cabbagelike plants, or pigs from wild boars?”Lynn Margulis, Dorion Sagan, Acquiring Genomes: A Theory of the Origins of the Species, (Basic Books, 2003), p. 29.