The Short Proof of Evolution
by
Ian Johnston
Malaspina University-College
Nanaimo, BC
[This document is in the public domain and may be used, in whole or in part, without charge and without permission, by anyone, provided the source is acknowledged. Last revised in March 2005]
--------------------------------------------------------------------------------
We live, we are constantly told, in a scientific age. We look to science to help us achieve the good life, to solve our problems (especially our medical aches and pains), and to tell us about the world. A great deal of our education system, particularly the post-secondary curriculum, is organized as science or social science. And yet, curiously enough, there is one major scientific truth which vast numbers of people refuse to accept (by some news accounts a majority of people in North America)--the fact of evolution. Yet it is as plain as plain can be that the scientific truth of evolution is so overwhelmingly established, that it is virtually impossible to refute within the bounds of reason. No major scientific truth, in fact, is easier to present, explain, and defend.
Before demonstrating this claim, let me make it clear what I mean by evolution, since there often is some confusion about the term. By evolution I mean, very simply, the development of animal and plant species out of other species not at all like them, for example, the process by which, say, a species of fish gets transformed (or evolves) through various stages into a cow, a kangaroo, or an eagle. This definition, it should be noted, makes no claims about how the process might occur, and thus it certainly does not equate the concept of evolution with Darwinian Natural Selection, as so many people seem to do. It simply defines the term by its effects (not by how those effects are produced, which could well be the subject of another argument).
The first step in demonstrating the truth of evolution is to make the claim that all living creatures must have a living parent. This point has been overwhelmingly established in the past century and a half, ever since the French scientist Louis Pasteur demonstrated how fermentation took place and thus laid to rest centuries of stories about beetles arising spontaneously out of dung or gut worms being miraculously produced from non-living material. There is absolutely no evidence for this ancient belief. Living creatures must come from other living creatures. It does no damage to this point to claim that life must have had some origin way back in time, perhaps in a chemical reaction of inorganic materials (in some primordial soup) or in some invasion from outer space. That may well be true. But what is clear is that any such origin for living things or living material must result in a very simple organism. There is no evidence whatsoever (except in science fiction like Frankenstein) that inorganic chemical processes can produce complex, multi-cellular living creatures (the recent experiments cloning sheep, of course, are based on living tissue from other sheep).
The second important point in the case for evolution is that some living creatures are very different from some others. This, I take it, is self-evident. Let me cite a common example: many animals have what we call an internal skeletal structure featuring a backbone and skull. We call these animals vertebrates. Most animals do not have these features (we call them invertebrates). The distinction between vertebrates and invertebrates is something no one who cares to look at samples of both can reasonably deny, and, so far as I am aware, no one hostile to evolution has ever denied a fact so apparent to anyone who observes the world for a few moments.
The final point in the case for evolution is this: simple animals and plants existed on earth long before more complex ones (invertebrate animals, for example, were around for a very long time before there were any vertebrates). Here again, the evidence from fossils is overwhelming. In the deepest rock layers, there are no signs of life. The first fossil remains are of very simple living things. As the strata get more recent, the variety and complexity of life increase (although not at a uniform rate). And no human fossils have ever been found except in the most superficial layers of the earth (e.g., battlefields, graveyards, flood deposits, and so on). In all the countless geological excavations and inspections (for example, of the Grand Canyon), no one has ever come up with a genuine fossil remnant which goes against this general principle (and it would only take one genuine find to overturn this principle).
Well, if we put these three points together, the rational case for evolution is air tight. If all living creatures must have a living parent, if living creatures are different, and if simpler forms were around before the more complex forms, then the more complex forms must have come from the simpler forms (e.g., vertebrates from invertebrates). There is simply no other way of dealing reasonably with the evidence we have. Of course, one might deny (as some do) that the layers of the earth represent a succession of very lengthy epochs and claim, for example, that the Grand Canyon was created in a matter of days, but this surely violates scientific observation and all known scientific processes as much as does the claim that, say, vertebrates just, well, appeared one day out of a spontaneous combination of chemicals.
To make the claim for the scientific truth of evolution in this way is to assert nothing about how it might occur. Darwin provides one answer (through natural selection), but others have been suggested, too (including some which see a divine agency at work in the transforming process). The above argument is intended, however, to demonstrate that the general principle of evolution is, given the scientific evidence, logically unassailable and that, thus, the concept is a law of nature as truly established as is, say, gravitation. That scientific certainty makes the widespread rejection of evolution in our modern age something of a puzzle (but that's a subject for another essay). In a modern liberal democracy, of course, one is perfectly free to reject that conclusion, but one is not legitimately able to claim that such a rejection is a reasonable scientific stance.
