Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
In 1909 the Russian botanist Konstantin Merezhkovsky introduced the theory of symbiogenesis. Merezhkovsky viewed living organisms as the result of a combination of two plasms: “mycoplasm” (stuff such as bacteria and fungi) and “amoeboplasm” (basically, eukaryotic cells without a nucleus). Merezhkovsky believed that mycoids were the food of amoeboids, and that one fateful day a mycoid managed to become the nucleus of an ameboid rather than its meal.
A fascination with the wonders of the bacterial world led the US biologist Lynn Margulis (since “The Origin of Mitosing Eukaryotic Cells”, 1966) to believe that no other single force has shaped evolution in a more important way. Everything the Earth is today, and everything that we and other living forms do today, is due to conditions that have been created and maintained by bacteria.
Margulis' fundamental thesis is that our bodies are amalgams of several different strains of bacteria. Endosymbiosis of bacteria is responsible for the creation of complex forms of life.
Margulis follows the US biologist Ivan Wallin, who (“Symbionticism and the origin of species”, 1927) was the first one to propose that bacteria may represent the fundamental cause of the "origin of species" (Darwin's unsolved mystery) and that the creation of a species may occur via endosymbiosis.
Margulis noted that not all the DNA is contained in the nucleus of the cell. As originally outlined by Wallin, The "mitochondria" are organelles of the cell that function as its "power plants": they convert sugar into energy that the cell can use. Mitochondria have their own DNA, separate from the DNA of the cell. While most DNA is organized as double sets of chromosomes in the nucleus, the DNA of mitochondria stands apart. Margulis believes that the presence of "extra" DNA in the cell is a fossil of an ancient evolutionary event: it attests to the fusion of at least two different kinds of organisms that together formed a "eukaryiotic" cell.
Margulis believes that such symbiotic merger, or "symbiogenesis", has been common in the evolutionary history of life on Earth, and actually accounts for life as we know it today. The ancestors of all life are bacteria. They fused into "protists" (algae, amoebas, etc) which fused into multicellular organisms. Margulis tracks their evolution into plants, animals and fungi.
Margulis emphasizes that the Earth is still dominated by bacteria, which not only account for the vast majority of life, but also maintain the conditions for life on the planet.
All life is either bacteria or descends from bacteria. Life "is" bacteria. Bacteria are also closer to immortality than animals with bodies: cell division generates identical bacterial copies of a bacterial cell. Bacteria can be killed but they do not really die, because countless clones exist of them. The life of a multicellular creature is far more fragile.
Bacteria can also reproduce at amazing rates, compared with "higher" forms of life.
Life can even be viewed as a plan for bacteria to exist forever: bodies are desirable food sources for bacteria, so one could view the evolution of bacteria into such bodies as a plan by bacteria to create food for themselves.
The biosphere is controlled mostly by bacteria, it is, in a sense, "their" environment, not ours. Margulis emphasizes that not only the atmosphere but even the geology of our planet is due to the work of bacteria (mineral deposits have been shaped by the work of bacteria over million of years, or by the reaction with the waste gas of bacteria).
We are allowed to live in it, thanks to the work of bacteria, which maintain the proper balance of chemicals in the air. If all bacteria died, everything would die. It is their world. Every other form of life exists because they exist.
On a smaller scale, if you "fumigated" your body and destroyed all bacteria that live in it, your body would not be able to perform vital functions, such as synthesizing vitamins, and would die.
The mitochondria, which dot all cells of all living beings, are former bacteria, using oxygen to generate energy.
The property of bacteria that intrigues Margulis is that they trade genes, rapidly and easily. DNA is loose inside bacteria's "bodies". Bacteria reproduce by simply splitting their DNA in two. This yields two offspring identical to the parent (same genes). Exchange of genes occurs only when genes are traded among bacteria. Bacterial sex ("conjugation") is about making a new bacterium out of an existing bacterium by adding genes donated by another bacterium.
The new bacterium resulting from the "engrafting" can even change sex, if the "sex" gene is received from the other bacterium (the "sex" gene specifies whether a bacterium is a donor or a receiver).
This process is not really related to our “sex”: sex is about two beings making a new being that partially inherits genes from each parent.
When bacteria "create" a new being, they do so by splitting (there is only one parent and the new being is identical to the parent). When bacteria trade genes, a being is changed into another being. Humans do not have either of these processes. I cannot split myself into identical copies of me, and I cannot mutate into another being by absorbing somebody else's genes. (Incidentally, bacteria can also trade genes as plasmids and viruses).
This process of "recombination" occurs even among bacteria of different species. It is as if I could absorb genes from an eagle and turn into a human with wings, and making children who will also be humans with wings. The genetic material of bacteria is extremely flexible and versatile.
Margulis thinks that this is the process that enabled life to evolve rapidly. Scale is crucial: what Margulis realized is the extent to which bacteria rule the planet. They account for a vast portion of the atmosphere and the geology of the planet.
They spread in ancient times and are still spreading today at fantastic speed. Any phenomenon that involves bacteria is involving billions of rapidly moving and mutating beings. Once life was created, once the first bacteria appeared, things happened quickly and on a massive scale. Bacteria spread quickly, thanks to their reproductive efficiency and to their ability to feed on ubiquitous organic compounds.
The first bacteria were "fermenters", feeding on the sugars available on the surface of the planet. They were followed by photosynthesizers: photosynthesis enabled these bacteria to feed on light. Then came bacteria ("cyanobacteria") that could tolerate oxygen, and could therefore feed on water (extract hydrogen atoms from water).
Each new type of bacteria was "polluting" the Earth and therefore changing the environmental conditions for future generations of bacteria. Pollution is an integral part of the evolution of life. The power of bacteria is that their "gene trading" habits made it relatively easy to adapt to whatever new conditions the climate and their own doing were producing.
The history of life is the history of a planet blanketed with rapidly reproducing and rapidly changing beings: the bacteria.
Protoctists were born about 2 billion years ago from the fusion of bacterial cells.
Eukaryotes (living beings whose cells have a nucleus and whose DNA is confined in that nucleus) evolved from those protoctists.
Mitochondria are visible remnants of this process of endosymbiosis.
Experiments by the Korean biologist Kwang Jeon showed that even virulent pathogens can become organelles (“Change of Cellular Pathogens into Required Cell Components”, 2006). Margulis concludes that predators can become symbionts, that a deadly infection can become a bodily part.
Margulis extends this paradigm to bodies made of several organs, and suggests that those organs also were accumulated the same way, that they are also due to the fusion with independent organisms by endosymbiosis.
While Darwin was emphasizing competition as the driving process of evolution, Margulis is emphasizing cooperation.
For Margulis life has "free will", and has used it to influence its own evolution. It is not only humans who can affect their environment to direct their own evolution: the whole environment is doing the same. Living beings make decisions all the time and are thus responsible in part for their own evolution, as first speculated by Samuel Butler.
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