The whole web of life in a single cell

November 12, 2014

Dominant evolutionary theory—“neo-Darwinism”—says that new species occur when genes mutate. Usually mutated genes make an organism less likely to survive and reproduce, but once in a great while, mutations provide an advantage.


The high school biology example is the peppered moth. Before the Industrial Revolution, most peppered moths were white. Once coal darkened the surfaces where the moths rested, birds found and ate them more easily. Darker moths lived to breed, and later generations were all dark. As the air became cleaner, the moths became light again.


But changes in moth coloration are just refinements. They aren’t a new species. In fact, we have never observed the beginning of a new species. The Darwinist idea remains dominant, but Lynn Margulis was somebody who had a better idea.

 

Margulis was born Lynn Alexander in 1938, and entered the University of Chicago at age 14. She was the first Mrs. Carl Sagan and published the groundbreaking On the Origin of Mitosing Cells.


Several journals rejected the book before it finally found a publisher in 1967. In it, Margulis describes the process by which bacteria combined, billions of years ago, to form the more complex cells of modern life.


For a couple million years, the only life on the planet was prokaryotes—cells that have no nuclei. One in particular, cyanobacteria, used sunlight to turn carbon dioxide and water into food and oxygen.


This was a disaster for a lot of other prokaryotes, because cyanobacteria were making a lot of deadly oxygen. But some prokaryotes liked oxygen. Other microbes preyed on these, but some of the oxygen-lovers survived, resulting in a partnership between the two organisms: One moved around and ate; the other handled all that nasty oxygen.


The oxygen-lovers became mitochondria, which help modern life forms, like us, breathe and metabolize food. You might say we are all naturally GMOs.


Margulis believed this endosymbiosis—not mutation—was the engine driving evolution, but biologists were slow to adopt her ideas, viewing them as a form of creationism.


New Age thinkers probably fueled this skepticism by embracing Margulis’ ecological unity without fully understanding it. In fact, Margulis collaborated with James Lovelock in developing the “Gaia Hypothesis,” a theory favored by New Age thinkers in which the totality of life on Earth maintains conditions optimum for itself—another, albeit macro, perspective on the unity of life.


Jan Sapp, a biologist at Toronto’s York University, gives four reasons for scientific reticence. One was the germ theory of disease. Scientists knew that some bacteria did useful things, but they remained suspicious.


Second, genetic theory held that inheritance happened through chromosomes. It hadn’t integrated the notion that other cellular odds and ends carry genes.


Third, evolutionary symbiosis happens in random spurts, conflicting with the orthodox idea that evolution happens gradually through the selection of mutations.


And, finally, 50 years ago, scientists lacked the technology to test Margulis’ ideas, which were not popular. She felt that science ignored 85 percent of evolution by focusing on only the last half billion years, but the late 20th century was a time in which science learned a lot about cells and about genetics.


Support grew, especially after scientists comparing mitochondrial RNA with nuclear RNA found that the mitochondria were more like contemporary prokaryotes than the nuclei in the cells where they lived.


The idea that species appear because of symbiosis still seems radical. A scientist named John Maynard Smith was at a conference and listening skeptically. He “commented that the phenomena discussed were not about macroevolution unless one could show that the behavior of the organism is changed.


“The next speaker...talked about microbial symbionts in weevils, which when experimentally removed, rendered the weevils unable to fly! We all turned to Maynard Smith. Good enough?”


Margulis financed her research with the honoraria from her lectures. She was warm and energetic, and entertained many friends in her Amherst home.


She championed the work of other thinkers, notably Robert Whitaker’s taxonomy, in which there are five kingdoms—bacteria protoctists, fungi, plants, and animals—rather than two.

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