A big step for bacteria

Bacteria, the simplest of the single-celled organisms, dominate almost all environments, surpassing all other living things in their habitat range and biochemical absorption capacity. The number of cells of the E. coli bacterium in each person's stomach exceeds the number of all humans who have ever lived * writes Stephen J. Gold

By: Stephen J. Gould

The textbooks of my youth described our current era as the age of man. Current linguistic preferences favor the "age of mammals". More generous people, and those with less curmudgeon tendencies, often choose to honor a most dominant multicellular group—numbering more than a million classified and described species (compared to the paltry 4,000 species of mammals)—and speak of the Age of Insects.
But all those suggestions are little more than the prejudiced and biased opinion of multicellularists. Today we are, as our planet has been for 3.5 billion years, in the age of bacteria.
Bacteria, the simplest of the single-celled organisms, dominate almost all environments, surpassing all other living things in their habitat range and biochemical absorption capacity. The number of cells of the E. coli bacterium in each person's stomach exceeds the number of all humans who have ever lived.
Bacterial life sprung up on Earth almost as soon as environmental conditions allowed it. About 3.9 billion years ago, the Earth's crust hardened. Undisputed bacterial life appears in the oldest rocks from 3.6-3.5 billion years ago.
From this short period we can only conclude that life of the bacterial variety has no difficulty developing on planets if only the appropriate conditions are at their disposal. The origin of life can be a virtually automatic result of carbon chemistry and the physics of self-organizing systems, in comfortable environments and when the inorganic components necessary for the process are present.
We have known for years that in the early history of Mars the appropriate conditions prevailed, which is characterized above all by evidence of water flowing on the planet. So if bacterial life developed at such a speed on Earth, and if similar favorable conditions existed on Mars at the time - we should have expected the discovery of the development of a certain form of bacterial life on Mars as well. With a little luck, evidence of such life could be preserved in the form of fossils in the rocks of the Red Planet.
This argument is prevalent among paleontologists already. Therefore I am extremely pleased - but not surprised - by the report on evidence of the existence of such bacterial life in fossils that was recently presented to the astonished world. Given this gap in response between me and most of you, I must ask why some seem to think that a standard and routine expectation of paleontologists now represents the greatest scientific revolution since Copernicus or Darwin.
I don't want to be grumpy, sour and suppress joy. While I'm not surprised by the revelation, I couldn't be more pleased. Science, after all, is based on factual documentation and not on superstitions, and a real fossil from Mars will be the crown jewel of the argument about life being a comprehensive and universal phenomenon (unless neighboring planets in our solar system can "seed" each other through the same meteor passage that brought the the rock from Mars to Earth).
However, a hypothetical argument for the plausible existence of fossils on Mars is not worth the effort of sending an email. Furthermore, and this is obvious, we need not be limited to the rare meteorites from Mars, which fortunately landed on our planet. We can go to Mars for a really systematic fossil hunt. The only real obstacles lie in the realms of politics and human will.
Two reasons underlie my quiet contentment and satisfaction. First, I am not sure that the argument for the right to life on Mars is correct (even those who claim it are not sure of this, and show admirable caution in an article on the subject that will be published soon). The meteorite is about 4.5 billion years old. The presumed fossil evidence appears on the surfaces of cracks within the rock. The authors provide solid arguments for the claim that the cracks were formed and filled about 3.6 billion years ago, when Mars had flowing water. But cracks are more problematic than the inner layers of the rock when it comes to identifying the sources of materials. The evidence of this life was made by chemical means and through straw - evidence that is not considered solid like bone or shell, which are unequivocal. The authors found organic chemicals and mineral deposits associated with the spherules that may have been formed in part by organic activity. On their surfaces they found shapes
oblong egg-shaped ones that look somewhat like the smallest bacteria. The spherules themselves are not fossils.
Three alternative interpretations exist for the findings: the existing evidence was created on Mars by non-organic processes; The evidence is organic, but it was created by organisms on Earth after the meteorite hit the South Pole; The evidence is organic, but it is the result of contamination in the laboratory. The authors of the article considered all the possibilities, and they present strong arguments - but no proof - to strengthen their position that the evidence was created by ancient organisms on Mars.
A whole world of conceptual differences separates bacteria from "little green people". We have good reason to think that life—even in its least complex form—represents a fully predictable and predictable onset of normal chemistry and physics on planets with the right conditions.
Complex, self-aware lives come into being through the very different path of historical contingency that is unintended, and completely unforeseeable. On Earth, only one fragile species - within 3.5 billion years - developed such a mental capacity, and it is not possible to detect any general trends in this direction on a planet that is still in the age of bacteria and is so completely controlled by insects among all its multicellular components.
Life on Mars provides a first evidentiary step towards the universalization of the age of bacteria. Humans remain the result of a spectacular and miraculous chance, as they have always been.
The author is a professor of biology and paleontology at Harvard University, and has written many books on these subjects