I know someone who is a deist, but looks on the Darwinian theory of evolution with disdain. To put it mildly, he doesn’t believe in evolution. He frequently posts article on the facebook page that he believes undermine the theory even if those articles are written by people who accept evolution and do not posit that their findings contradict the theory. For instance: Widespread horizontal transfer of retrotransposons and Bacteria May Readily Swap Beneficial Genes: Microbes Trade Genetic Coding for Antibiotic Resistance and More. I say that to say this: in my previous post on evolution, I criticized its supporters’ chronic lack of civility, from insisting that those who reject evolution do so because of their religion to calling them stupid, ignorant, and wicked. I’m newly short tempered so anyone who issues such responses on this post is in for a surprise (no, you will not be banned).
Evolution in Theory
One can explore the theory of evolution in two ways. Firstly, by thinking about it and evaluating its plausibility and possibility and secondly by exploring the physical evidence to see if it really did happen. This is an important distinction because it is perfectly possible for a theory to be both plausible and possible, but not be the case. By way of illustration, it is possible that I cheated on my JSCE. It is also plausible because I, being human, often do wrong things. But it did not happen. On the other hand, if an idea is possible but not plausible, one can rationally reject it in the absence of very strong evidence in its favor.
Is Evolution Possible?
The theory of evolution goes something like this: Organisms adapt to their environment. Organisms of the say type often vary in specific ways. If one of those organisms is different from others in a manner that benefits it, it is more likely than its peers to survive to maturity and pass on its genes. This creates a slow shift in which said characteristic becomes dominant in that species. If this goes on long enough, you eventually get a type of animal very different from the original. This process of change as a result of natural selection is referred to as evolution. Note that in order for this to work, those traits being selected must be genetic or they could not be passed to offspring.
Of course, natural selection won’t work on its own because you need the group of organism to possess genetic characteristics different from each other. Or there will be nothing to select. Think of the very first living cell. It produced offspring and passed its characteristics to them. How then did those offspring become different from each other? That would only happen if the organism failed to pass on its genes faithfully to its offspring.
So the theory of evolution can be summarized thus: Genes can be mutated, creating diversity in the offspring of a particular organism. Those organisms are then selected by their environment because those best able to reproduce do better than the rest. If this process goes on long enough, we get a huge array of living organisms.
I have told a story that sounds possible. It could happen. So did it?
Is Evolution Plausible?
The whole bulk of evolution hinges on the issue of mutation. Without that, there would be nothing to select. If the first species was terribly unsuited for its environment, it would simply die out. Even already existing species could not change into new ones. Each species would have to be built from scratch. I don’t know anyone who thinks that humans could be built from scratch with no guiding intelligence. We haven’t even been able to build a single cell with guiding intelligence. So, even if that was possible, it would take a damned long time for the diversity we see to appear; probably longer than the earth has existed.
So, is it plausible that millions of mutations produced the diversity of life on earth? Let’s first get something out of the way: mutations happen. That said,
1. Most mutations are harmful: To make that obvious, consider this example from the University of Utah’s genetics program
Dividing the string into three letter words produces a sensible sentence: “The sun was hot but the old man did not get his hat.” You can try to mutate the sentence, but you’re more likely to get a nonsense statement than a sensible one. For instance, let’s pick a letter to mutate. The ‘b’ in ‘bat’. If we mutated the ‘b’ to ‘h’, we would get ‘hat’ and the sentence would still make sense (somewhat. It wouldn’t get a good grade). However, most of the letters of the alphabet won’t have the same effect. If you picked a letter of the alphabet at random, you would most likely get something like an ‘e’ or a ‘g’, which when substituted for the ‘b’ in ‘bat’, completely ruins the sentence. So going on blind chance only, it is pretty darn unlikely that a mutation would produce a good result.
This ‘bad luck’ can be worked around. As this source makes clear, if the organism accidentally gets two copies of the same gene, one copy can be mutated while the other remains the same. That way, as long as the mutated gene doesn’t dominate the other, work can be done on the other one without killing the organism. Remember that these mutations are all happening by pure chance. Don’t imagine that there are some intelligent choices are being made.
The one issue I instantly see with this is that the mutated gene cannot be selected if it is not in effect. However, if it is in effect, this particular benefit arising from the duplication would be of no use. So, this requires that all modifications of the gene be mutations and that those successive mutations eventually produce something useful. Then that gene has to become dominant.
Here’s the math*:
P1 = Probability that a gene is duplicated X Probability that one of the genes is mutated beneficially X probability that the mutated gene is not dominant (at all stages of its mutation) X Probability that if and when the gene eventually comes online, the changes it has are beneficial.
You can probably tell that I’m not very optimistic about the chances.
2. It gets worse. After all the trouble necessary to create a working mutation, most mutations affect only a single protein product; a tiny change. So in order to create an organism with phenotypic (visible) differences from its parent, you need a lot of mutations. You need the group of genes responsible for that characteristic to be mutated in specific beneficial ways such that they are still compatible with each other. The previously mentioned article argues that this problem can be made easier. Often, some of the genes in that group have a bigger effect than others. So, the more of the more important genes mutated, the more significant the changes in the phenotype. It’s not a breakthrough but it moves the necessary events from really really really unlikely to about really really unlikely.
P2 = Probability that all the genes responsible for said trait are mutated (or not) in beneficial and compatible manners.
So, the composite probability that a minuscule change in the characteristics of a species occurs = P1 X P2. Fat chance, huh? And we haven’t even specified that the change in phenotype be beneficial (note that this is different from the change in the genes being beneficial), nor have we gotten into the details of natural selection.
I’m a huge believer in chance. If a mail arrives in my box with the name of a high school classmate on it and she doesn’t even know my address, I’ll chalk it up to chance. However, If I arrive home to find a beautiful intricate house of cards on my dining table, you’d better believe I’d be looking to see who broke in. It’s possible that the cards just fell of a shelf and happened to make that house, but I’ll probably never believe that.
This does not mean that evolution didn’t occur – even a little bit. But it does predispose me to the belief that it is not the sole explanation for the diversity of life on earth. It’s possible, but not plausible. My next post on this topic will explore the question of whether there is evidence for the theory.
* My probability might be rusty. If I made any huge mistakes, please point them out. The calculations are only supposed to be approximate.