The April, 2010 edition of Discover Magazine profiles biologist Lynne Margulis, famous for her well accepted suggestion that eukaryotic bacteria did not evolve in linear fashion, solely as as a result of natural selection. Rather,
mitochondria and plastids–vital structures within animal and plant cells–evolved from bacteria hundreds of millions of years ago, after bacterial cells started to collect and interactive communities and live symbiotically with one another. The resulting mergers yielded the compound cells known as eukaryotes, which in turn gave rise to all the rest-the protoctists, fungi, plants and animals, including humans.
There was a shocking idea at the time (1967), but, as described in this article by Dick Teresi, the more recent ideas of Margulis are even more controversial. The Discover Magazine article documents her arguments that symbiosis is “the central force behind the evolution of new species.” This position runs counter to the holding of modern conventional scientific wisdom, that new species arise through “gradual accumulation of random mutations, which are either favored or weeded out by natural selection.” Margulis holds that random mutation and natural selection play a minor role and that the big leaps in the evolutionary record “result from mergers between different kinds of organisms, what she calls symbiogenesis.”
The Discover article takes the form of an interview, in which the dominant theme is that “natural selection eliminates and maybe maintains, but it doesn’t create.” Margulis argues that the laws of genetics “show stasis, not change.” She was prompted by the fact that there is no record of major fossil change until 542 million years ago, yet all of a sudden we see the Cambrian explosion. Stephen Jay Gould coined this phrase, “punctuated equilibrium,” “to describe a discontinuity in the appearance of new species.” According to Margulis, her explanation of symbiogenesis explains these discontinuities and should thus be considered the primary mechanism for evolution.
Margulis carefully distinguishes her approach from arguments based on “intelligent design.” She holds that those who advocate for “intelligent design” have nothing meaningful to offer to the scientific conversation.
In the Discover article, Margulis points out that “all visible organisms are products of symbiogenesis, without exception. The bacteria are the unit. . . . Symbiogenesis recognizes that every visible life form is a combination or community of bacteria.” She gives examples of mitochondria and chloroplasts.
Margulis describes how bacteria could become part of the cell of another organism:
At some point an amoeba ate a bacterium but could not digest it. The bacterium produced oxygen or made vitamins, providing a survival advantage to both itself and the amoeba. Eventually the bacteria inside the amoeba became the mitochondria. The green dots you see in the cells of plants originated as cyanobacteria. This is been proven without a doubt . . . I believe in acquired genomes.
She argues that evolutionary biologists “are basically anthropocentric zoologists.”
They’re playing the game while missing four fifths of the cards. The five are bacteria, protoctists, fungi, animals, and plants, and they’re playing with just animals–a fifth of the deck.
How important are bacteria?
We couldn’t live without them. They maintain our ecological physiology. There are vitamins and bacteria that you could not live without. The movement of your gas and feces would never take place in the bacteria. There are hundreds of ways your body wouldn’t work without bacteria. Between your toes is a jungle; under your arms is a jungle. There are bacteria in your mouth, lots of spirochetes and other bacteria in your intestines.… Bacteria are our ancestors.
What else does Margulis have to say that is controversial? Quite a bit. She holds that HIV is not an infectious virus “or even an entity at all. There is no scientific paper that proves the HIV virus causes AIDS.” She also holds that penicillin does not kill syphilis. “If you really get syphilis, all you can do is live with the [oftentimes dormant] spirochetes. She argues that “consciousness is a property of all living cells. She holds that human beings are “mammalian weeds… Like many mammals, we overgrow our habitats and that leads to poverty, misery and wars.
I found this to be a well-written article about a thoughtful and provocative scientist.