Lynn Margulis has an interesting interview in Discover Magazine, where she puts forth symbiogenesis as the most important mechanism in marcoevolution.

I find her claims about AIDs implausible, to say the least.

Nonetheless, her arguments for symbiogenesis stand. I'd been aware of the way many organisms intertwined with others, but had never taken this to challenge evolution as tree shaped before. She's lead me to challenge much of what I'd taken for granted in evolution.

Natural selection eliminates and maybe maintains, but it doesn’t create.

Punctuated equilibrium” was invented to describe the discontinuity in the appearance of new species, and symbiogenesis supports the idea that these discontinuities are real.

The point is that evolution goes in big jumps.

Long-term symbiosis leads to new intracellular structures, new organs and organ systems, and new species as one being incorporates another being that is already good at something else. This major mode of evolutionary innovation has been ignored by the so-called evolutionary biologists.

The evolutionary biologists believe the evolutionary pattern is a tree. It’s not. The evolutionary pattern is a web—the branches fuse, like when algae and slugs come together and stay together.

From the very beginning the Russians said natural selection was a process of elimination and could not produce all the diversity we see. They understood that symbiogenesis was a major source of innovation,...

In 1924, this man Boris Mikhaylovich Kozo-Polyansky wrote a book called Symbiogenesis: A New Principle of Evolution, in which he reconciled Darwin’s natural selection as the eliminator and symbiogenesis as the innovator.

Sensory cilia did not come from random mutations. They came by acquiring a whole genome of a symbiotic bacterium that could already sense light or motion. Specifically, I think it was a spirochete [a corkscrew-shaped bacterium] that became the cilium.

If I’m right, the whole system—called the cytoskeletal system—came from the incorporation of ancestral spirochetes. Mitosis, or cell division, is a kind of internal motility system that came from these free-living, symbiotic, swimming bacteria.


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I'm a skeptic at heart, especially when it comes to stuff that's related to the scientific method of inquiry.

Symbiogenesis is nowhere close to being a well-established scientific theory.

He're a good counter read on the subject:

Lynn Margulis (1938-2011). 

"The evolutionary pattern is a web—the branches fuse, like when algae and slugs come together and stay together." 

The Micro-structure

"As the passing of the great biologist Dr. Lynn Margulis is mourned worldwide, let us not forget what she has done. The endosymbiotic theory was first proposed by her in the 1960’s. At first many were skeptical but when evidence turned up, it was accepted. Without it, our knowledge of cells would not be what it is."
~ Fractal Explorer

@Ruth: I have heard others question the role of HIV with AIDS. Can you define your thought of implausibility? 

She's best known for her work eukaryotic cells and the endosymbiotic theory, but her assertions on symbiogenesis are far from well-founded. She also ran into quite a bit of controversy within the scientific community in recent years:

Oh yes! Margulis ran into a lot of controversy about her theory ... but so did 

Galileo Galilei

Nicolaus Copernicus

Alfred Wegener

Robert Koch

J Harlen Bretz

I could add more, but you get the idea. Now, that established, can you give reasons why "her assertions on symbiogenesis are far from well-founded." I don't know anything about biology. 

"I greatly admire Lynn Margulis's sheer courage and stamina in sticking by the endosymbiosis theory, and carrying it through from being an unorthodoxy to an orthodoxy. I'm referring to the theory that the eukaryotic cell is a symbiotic union of primitive prokaryotic cells. This is one of the great achievements of twentieth-century evolutionary biology, and I greatly admire her for it."

~ Richard Dawkins

Lynn Margulis

Joan, AIDS deniers don't have evidence for their different views about HIV virus. Some, like Dr. Margulis, claim another kind of infection, most commonly syphilis, is the true cause. At the beginning of the AIDS crisis (then known as GRID - gay-related immunodeficiency disease) many patients had a history of syphilis too. The problem is the great majority of patients never had syphilis. The early finding was sample bias, or the fact that the clusters of men first recognized were noticed because they all came from small geographical and social communities who spread more than one STD among themselves. Later versions of this such as Dr. Margulis' writings posit opinion as facts. Her statement about syphilis as "The Great Imitator" is true as far as it goes. The problem with that is you can claim virtually any disease as being syphilis because it's symptoms are so varied.

As a physician on the frontlines of the epidemic I can give you more about how the identification of HIV as the cause came about, changed everything about how patients were cared for, and led to the current anti-retroviral drugs extending the lives of many people, and preventing fetal transmission of the virus. This understanding also led to safe-sex practices as routine, testing of all blood products, and developing ways to protect healthcare workers from getting blood-borne illnesses. Other AIDS deniers say it's a plot by western nations, or pharmaceutical companies, or because victims of the disease have poor behaviors. One only has to look to Asia and especially Africa to see the terrible results when governments deny AIDS and the RC Church denies condom use.

Jessica, thank you for this information. Certainly, the complexity of the disease and its social implications require more than opinion. There is a newscaster who adamantly declares there is no connection between HIV and AIDS. I haven't had a TV for several years and don't remember his name, however, if anyone knows of whom I speak, please invite him to check his sources. 

I'm not familiar with the research, but the molecular structure of HIV is well known. I can't believe the original researchers failed to use standard protocols for verifying an agent as a cause of a disease. Nor is it plausible to me that so many scientists could fail to notice syphilis or another spirochete, even if it were usually in a dormant state. The genetic code would still be in infected cells even if the spirochete form were no longer maintained. To me that particular claim isn't plausible at all, that she looked for evidence and didn't find any.

What do you suppose was Margulis' motive for looking and not finding any?  

The standard protocol for identifying an agent as the cause of a particular disease is to extract the disease agent from an infected animal, and then put the agent (and only that agent) into healthy animals, then extract same agent from them after they come down with the disease. If the HIV retrovirus can cause AIDS in healthy specimens, and then we find them full of that same retrovirus, that's fairly solid evidence. Perhaps they didn't do exactly this protocol because you can't experiment on human beings, but there are animal equivalents of HIV. There are so many AIDS researchers, working with so many different experimental designs. How could all of them have missed a spirochete? The only argument I saw in the article was that syphilis was the cause was that it has similar symptoms and can look like other diseases, which is superficial and not evidence of cause.

Her claim that the entire cytoskeleton evolved from spirochetes is far more plausible.

Thanks Ruth. What seems plausible to an uninformed one such as myself, and your clarity and Jessica's, and the Pauling effect from Lightnin' helps to understand why it is not something that stands up to scrutiny. I appreciate you all. 

Thanks for that link Lightnin'. I like the term "Pauling Effect". Dr. Margulis was a very well respected scientist whose work about symbiogenesis and evolution, with certain early bacteria becoming mitochondria and chloroplasts used in all multicellular organisms, is well accepted as true and has led to rethinking how different modes of evolution work together. She had strong self-belief that meant she continued that work despite ridicule. Her later writings supporting the Gaia hypothesis and AIDS denial as a continuation of symbiogenesis go against scientific facts and Lightnin's link is an excellent summary of many great scientists who later in life get strange ideas that get taken as proved because of their reputation.

Two sites with excellent resources about these and other evolution questions are and and both also debunk anti-evolution and Intelligent Design arguments.

Lynn Margulis died last November, not too long after that interview was published. The NYT had this obituary:

She was married to Carl Sagan at one time.

Thanks for introducing me to the Pauling Effect, Jessica. I didn't realize she'd been married to Carl Sagan.


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