Serial Endosymbiosis Theory

From P2P Foundation
Jump to navigation Jump to search

= Thesis on biological evolution by Lynn Margulis: qualitative jumps in evolution depends on symbiosis with other living beings



(from an interview conducted by Caroline Picard)

Graham Harman:

"The usual pseudo-cutting edge model in which everything is in a constant flux of becoming. This merely levels out everything in such a way that all moments become equal, which does not match what experience teaches us. In Immaterialism I try to identify five or six particular moments that were crucial for the life of the Dutch East India Company. My major source here is the Serial Endosymbiosis Theory (SET) of the biologist Lynn Margulis, who is only just starting to catch on in the humanities: Luciana Parisi at Goldsmiths in London and Myra Hird at Queen’s University in Canada come to mind as two authors working in neighboring areas to my own who have grasped the importance of Margulis for all of us. For those who haven’t read her but are interested, the book Symbiotic Planet is a good starting point.

Margulis had an important idea in the 1960s, during her years as a graduate student and assistant professor, that life forms evolve primarily not through a gradual process of survival of the fittest, but through intermittent symbiosis with other life forms. Consider the human cell and its numerous organelles. Her theory was that these organelles did not originally belong to the human cell, but came from the outside. Originally, there was the prokaryotic cell, which has no nucleus or internal membranes. According to Margulis, these organisms were probably infected by cellular parasites that fed on the nutrients inside the cell. Eventually, the parasites became important for our cells to survive when atmospheric oxygen drastically increased.

Margulis hypothesized that if we were ever able to run adequate tests to analyze the DNA in the nuclei of human cells, we would find that the cellular DNA does not code for all the organelles, thereby proving their extra-cellular origin. In the 1980’s those tests became possible and it turned out that Margulis was right. What she had proposed went from being a laughingstock of a theory to standard textbook biology.

* CP: Is there another example of how that would work?

GH: Yes. Around the same time, Margulis asked, “Have we ever seen evolution happen in a laboratory?” They told her there was one such case, and it involved fruit flies in a tank, if that’s the proper term. Researchers split the tank down the middle, slowly turning the heat up on one side and down on the other. After however many generations, the two sets of fruit flies could no longer mate., and thus had effectively become different species. After dissecting them, they found that there was a virus in the hot fruit flies. The orthodox reaction to this might have been: “Damn it. The experiment is contaminated by a virus. It’s useless.” But the reaction of Margulis was different: “No. That’s the whole point. The point is that the virus allowed the fruit flies to survive in the heat.”



H.J. Spencer:

"Even though Margulis writes that the central idea of SET is that new species arise from symbiotic mergers among members of old ones she is correct in stating that this aspect is not even discussed in polite scientific society: a fact confirmed in the Oxford Dictionary of Biology entry on 'Endosymbiont Theory' that totally ignores this radical feature. Margulis describes the four stage mergers, each involving symbiogenesis, in the evolution of plants, with their large cells and observable organelles to finally produce green algae. She begins with the mobile spirochetes (corkscrew body) absorbing the heat-loving archaebacterium (oldest forms of bacteria) to form the nucleocyto-plasm - the principal substance of the ancestors of animal, plants and fungal cells. The next merger was a swimming protist (nucleated micro-organisms)that is an anaerobe (poisoned by oxygen), merging with an oxygen-breathing bacterium; this then was absorbed by the modified spirochete from the first step, now thought to have occurred about 2,000million years ago. The final merger occurred when the 'triple combo' incorporated with swimming green algae that have become blue/green cyanobacteria (both forms contain chlorophyll, capable of photosynthesis). This final contribution eventually became the chloroplast organelles in plants. A similar evolution occurred in the ancestors of animals: the 'trapped' bacteria became animal organelles."