The Debt We Owe Bacteria

Life has survived for nearly 4 billion years on the planet. This implies, according to neo-Darwinian thought, that conditions have fortuitously been within the range of values within which organisms could adapt through natural selection. Is this view correct? Not according to Lovelock.

Lovelock, in agreement with the neo-Darwinians, argues that the continuance of life on this planet necessarily demands that conditions be compatible with the integrity of the cell membrane. Unlike the neo-Darwinians, however, he also argues that the conditions compatible with the integrity of the cell membrane, being very restrictive or of a very narrow range of values in its relevant variables, are unlikely to have kept for as long as the neo-Darwinians apparently assume. He argues that life, through bacterial activity, must have intervened to maintain conditions hospitable to life. Otherwise, if bacterial intervention had not taken place and the planet evolved according to the laws of physics and chemistry alone, then “all possible chemical reactions capable of taking place from micro-level interactions” would have “taken place.” This would mean, “[f]or example,” that “two gases, such as oxygen and methane, that react with one another, could not be expected to indefinitely co-exist in the atmosphere.” Instead, we would expect to find “equilibrium gases of  a generally unreactive nature, such as carbon dioxide.”

What  we find on Earth, however, is “oxygen and methane co-existing with one another and carbon dioxide present only in trace amounts.” Such a state of remove from equilibrium conditions (which equilibrium conditions correspond to death or the absence of life) “argues the presence of processes” that maintain that remove – bacterial activity.

This bacterial activity, according to Lovelock, initiated “in the Archaean eon, spanning 3.7 to 2.5 billion years ago.” Through the reciprocal selective action of prevailing environmental conditions that they adventitiously improved, bacteria coordinated themselves “as cooperative communities of bacterial mats on lagoons or as communities on rocky substrates that were being transformed into structures called stromatolites (some of them as big as houses). Such bacterial communities continue to be found today.”

Through such cooperative communities, bacterial activity has been responsible for maintaining the far-from-equilibrium physico-chemical conditions of, for example, “ ‘temperature, salinity, acidity, redox potential, water availability,’ ” compatible with the integrity of the cell membrane. Thus, as concerns water availability, for example, “without the hydrogen sequestering action of bacteria that derive their metabolic energies from the synthesis of hydrogen sulphide; and without the oxygen released by photosynthesizing bacteria that combine with available atmospheric hydrogen to form water, hydrogen released from the reaction of water with rocks (in the presence of carbon dioxide) would, in a period of 1 or 2 billion years, have caused all the water in the oceans to have effectively evaporated through eventual escape of hydrogen into space.”

Bacteria may, therefore, be rightly viewed as the pillars of life on this planet. It must and should be an embarrassing object lesson for our species, however, that bacteria, without benefit of brains, spontaneously cooperated to achieve this desirable end. Meanwhile, our species, in competition with each other and other species, is precipitating the sixth great extinction episode on this planet.

(References: Lovelock, James. 1991. Healing Gaia: Practical Medicine for the Planet. New York: Harmony Books; Velasco, Horacio. 2008. “Sustainability: The Matter of Time Horizon and Semantic Closure”. Ecological Economics, 65, pp. 167-176)