In a new study Life Before Earth, Alexei A. Sharov and, Richard Gordon argue that the complexity of life grows exponentially over time in a manner similar to Moore’s Law. They “measure genetic complexity by the length of functional and non-redundant DNA sequence rather than by total DNA length.” When they plot this measure on a graph with representative types of organisms they find the greatest complexity found in life on Earth at any point in time doubles every 376 million years. If the line on the graph is extended backward, the beginning point of the line, the hypothetical beginning of life, is about 9.7 billion years ago. This is before Earth existed. From that, they conclude that life must not have originated not on Earth.
While I am not totally convinced of their argument, the authors certainly raise some provocative questions.
The most important is what predated the most primitive organisms on Earth. The accepted theory is that the earliest forms of life on Earth were prokaryotes. These are organisms without a nucleus and include among them bacteria. Part of the problem is that these organisms are already fairly complex so it is almost impossible that one of these assembled randomly. So the authors argue that life may have begun with something as simple as one nucleotide and evolved greater complexity via an evolutionary process over 5 billion years to reach the level of complexity of the prokaryotes. This evolution took place probably in some special environment unlike Earth.
Another conclusion is that intelligence and consciousness are related to genetic complexity. The complexity found in humans required almost 10 billion years to evolve. Therefore, intelligent life in the universe is only now emerging. Intelligent beings could not have seeded the earliest life to Earth because there was insufficient time for them to have evolved. The earliest prokaryotes arrived on Earth from spores carried by comets and asteroids. This suggests that we will likely find life much like that on Earth on other planets in our solar system and probably throughout the galaxy.
The authors finally try to draw some conclusions about the future. Genetic complexity may only be a good measure of intelligence on the lower end of the spectrum and now genetic complexity may be lagging behind growth in intelligence. They make a distinction between the growth rates of human technologies, such as computer speed, and the functional complexity of human civilization which might better measured by such things as number of scientific papers or number of patents. They find functional complexity doubles approximately every generation. “In summary, the functional complexity of human civilization grows exponentially with a doubling time ca. 20 years, but we do not see any signs of an approaching ‘technological singularity’ when humans would be replaced by intelligent machines. Instead, we expect a stronger integration of human mind with technology that would result in augmented intelligence.”
Although this study is fascinating, I think the question of whether the first organisms developed solely by evolutionary forces is still open. There may have been supplemental forces of some type at work. Evolutionary theory suggests that organisms evolve by random mutation. Therefore, a mutation could create a more genetically complex species, one equally complex, or a simpler one, although probably the odds of doing each are not equal. It would seem that prokaryotes in natural or laboratory settings ought to mutate occasionally into simpler organisms. If this were observed, this could provide a clue to what preceded the prokaryotes and whether evolutionary forces created the first organisms or some additional mechanism was at work. If it were some other mechanism, the development of the prokaryotes that required 5 billion years in this study may have taken place more quickly.