What Is Evolution?
Are Humans Evolving?
Essays & Articles
Central Dogma of Molecular Biology
How Many Genes Do We Have?
Random Genetic Drift
Evolution and Abiogenesis
v2.0 ©2006 Laurence A. Moran
Science v. Religion
hen we use the term "biological evolution" we have to have a consensus opinion on what this actually means. Is it some warm fuzzy notion about how change affects anything that has to do with life? If this is what we mean by biological evolution then it will probably include all of those changes that took place before free-living organisms arose. On the other hand, if we stick to a more scientific definition of evolution some biological changes won't be included. The question is whether the origin of life, or abiogenesis, is part of evolution or something separate.
I think there's a scientific definition of biological evolution that has proved to be very useful in biology. It requires (by definition) populations of living organisms. Anything that preceded the formation of such populations is obviously relevant but it ain't biological evolution. Now, we could change the definition of biological evolution to include the formation of the first molecules that gave rise to living things but this would create more problems that it solves. We would still need a term for the evolution of populations by changes in the frequencies of their alleles.
There's also a political consideration. Many people don't believe in biological evolution. I'd like to convince them that evolution, the process, is a fact. It's also a solid scientific fact that modern organisms evolved from a common ancestor that lived billions of years ago. These facts encompasses what I believe to be the core concepts of biological evolution. We have a chance to educate the public on this point. If people want to believe that the first living organism was created by God then I can live with that for the time being. First things first. Let's work on the evidence for biological evolution and not burden ourselves by linking it, incorrectly in my opinion, with the creation of life. That strategy is doomed from the beginning.
I would say there's a form of "evolution" called chemical evolution. This contributed to the formation of the first living cells. There might well have been a form of selection among replicating molecules and there might well have been chance events that led accidentally to the enrichment of some other molecules. These two processes resemble natural selection and drift in the same way that those processes are echoed in genetic algorithms. However, it is useful to have a better working definition of natural selection (and drift) that applies to modern species. This definition requires populations of living organisms in order to have any usefulness. It isn't helpful to extend the definition of "natural selection" to the level of replicating molecules. If we do that we'll need a new term to represent the kind of mechanism that explains the evolution of the peppered moth and Galapagos finches. That new term will exclude selection of replicating molecules. The real question is whether the selection of replicating molecules and biological natural selection are the same phenomena. I don't think they are - this doesn't deny that there are similarities ... of course there are similarities.
I would say that abiogenesis is not the same as biological evolution and it certainly isn't the same as "Darwinian evolution". I would argue that the origin of life was a spontaneous process that did not require anything out of the ordinary and certainly didn't require a supernatural being. However, I would also argue that biological evolution only began with the formation of the first population of living cells.
Some scientists have argued that it's silly to exclude the origin of life from our definition of evolution. One of them suggested an analogy between the study of geology and the origin of the Earth. He claimed that the origin of the Earth is part of what geologists study. Therefore, according to him it would be silly to separate out geology and the origin of the Earth. I agree.
The origin of life is part of biology. However, it isn't necessarily part of biological evolution. A better analogy might be plate tectonics and Earth's origin. Lots of geologists study plate tectonics. The movement of plates helps us understand much of Earth's history. It's obvious that the geological activity of our planet originated when it formed 4.5 billion years ago. However, the actual condensation of Earth from stellar gasses is not plate tectonics. The geological processes of rift formation, subduction, plate movement, hot spots, etc. didn't begin until the Earth had cooled sufficiently to present a solid surface. I see biological evolution as similar to plate tectonics in geology. There's a connection with origins but they aren't the same thing.