Can Evolution Explain Our Origins?
Atheists often characterise arguments for God’s existence as “God-of-the-gaps” arguments. By this they mean that God is invoked to explain the otherwise inexplicable, to bridge the gap between what we can understand about the world and what we in fact see around us.
As a counter to such arguments, atheists tend to invoke modern science. Science, they say, can now explain all those things that were previously taken to support belief in God. We no longer need to invoke God as an explanation of them; the explanatory gap has been closed.
One example of this concerns the question of our origins. The argument from design argues that the only adequate explanation of how we got here is that there is a God that created us. Some forms of the argument support this suggestion by looking at human biology.
Consider the complexity of the human eye, for example. Some have thought that the eye is no less clearly a product of intelligent design than a machine like a watch. Its complex parts work together in harmony to some purpose; it must, therefore, have been created for that purpose by God.
Atheists often respond to such arguments as this by citing evolution theory. Evolution theory, they say, can fully explain the appearance of design in the world around us. There is no longer any need to look to religion for an answer to the question of our origins.
The explanation of the origin of life offered by evolution theory is roughly this:
Once upon a time, there was no life. By chance, there came to be simple organisms capable of replicating themselves. Random mutations introduced variety into the population of these organisms, with the result that some of them were better able to survive and replicate themselves than others. A scarcity of the resources necessary for these organisms to survive and reproduce introduced competition between them. Those least fit for competition were unable to secure the resources that they needed, and so died without reproducing.
Those best able to compete multiplied, with random mutations again introducing further variety. As this process was repeated, the organisms developed on an upward curve: each round of mutations introduced better organisms, and each round of competition killed off the weaker organisms. We are the result of the repetition of this process over millions of years.
Perhaps the most important Creationist response to this has been to appeal to irreducible complexity. An organism is irreducibly complex if taking away some of its parts doesn’t just make it work a little worse, but makes it not work at all.
An illustration of irreducible complexity is a mouse trap. A mouse trap consists of several elements: a flat platform, a spring, a trigger, an arm, and some cheese. A mouse trap with all of these elements will work well. A mouse trap that lacks any one of these elements, though, won’t just not work well, it won’t work at all.
If there is no platform to which the other elements can be attached, then the mouse can grab the cheese from the unassembled mouse trap with impunity. If there is no spring, then the mouse will set off the trap, but the arm won’t snap down on it. If there is no trigger, then the mouse can grab the cheese without setting off the trap. If there is no arm, then it doesn’t matter that the mouse sets off the trap. If there is no cheese, then the mouse won’t go anywhere near the trap. To have a mouse trap that functions at all, then, you need every one of these elements; if you’re missing any of them then it just won’t work.
Evolution theory holds that we have evolved incrementally over time, gradually changing from one state that works to another state that works better. If evolution theory is true, therefore, then there must be a succession of states, each of which allows us to survive, through which we have evolved on an upward curve.
This, though, doesn’t seem to be the case; we seem to be irreducibly complex. To illustrate (actual examples are a bit more complex than this): think of the organs that make human beings work, our hearts, lungs, stomachs, brains, etc. A human being that lacks any of these won’t just have less survival value than one with all of them; it won’t have any survival value at all. A human being without a heart is a dead human being, as is one without either lungs, or a stomach, or a brain. We therefore can’t have incrementally acquired these things, first getting one, then another, and so on; we must have acquired them all at once. That, though, isn’t evolution. Evolution is a gradual process.
Evolution, then, cannot explain the origin of irreducibly complex biological organisms. If (and that's a big "if") we are such organisms, then there must be more to how we got here than evolution.
Evolution and Consciousness
A second problem for evolution theory is that of explaining the origin of consciousness. Human beings are not just physical systems; we have rich mental lives. There is more to this mentality than electrical events in the brain. For any mental state, there is a physical event (what is going on in the brain) and a mental event (what that feels like for us). The two are, at least in principle separable; there’s no logical contradiction in having one without the other.
The process of natural selection selects organisms for survival based only on their behaviour, on what they do. An organism that behaves as we behave but which does not have the attendant mental states that we have will have just as much survival value as we do. Mentality is not necessary for behaviour, and nothing more than behaviour is necessary for survival, so there is no survival value to having mental states.
Evolution theory, though, can only explain the origin of traits that have survival value. For example, we have two eyes rather than one, according to evolution theory, because that makes it possible to judge distances more accurately, increasing our chances of survival. Consciousness, though, does not increase our chances of survival; we are no more likely to survive than we would be if physical events in our brain did not give rise to conscious experiences, if our decisions just happened automatically as in a computer.
Evolution theory, therefore, cannot explain the origin of consciousness.
Evolution and Chance
Let’s set those problems aside for a moment, though, and suppose that evolution theory can explain how complex biological organisms could arise on this planet. Does this solve the mystery of how we in fact did come to be here? Arguably not. It is sometimes argued that even given the coherence of evolution theory, it is still highly unlikely that unguided natural processes would give rise to life in the time-frame that evolution theorists say that this has happened.
Life on Earth is phenomenally complex. Given the degree of complexity that it exhibits, it is claimed, there simply hasn’t been enough time for it to be likely to arise through evolutionary processes. Even if it were possible for life to come from non-life via a process of evolution, according to this view we would not expect it to have done so yet. If life evolved, then it is therefore likely that its evolution was not random, but rather was guided by God’s hand.
It is thus argued that unless we introduce God evolution theory is inadequate as an explanation of our origins, that natural selection won’t work as an explanation on its own.
Prerequisites for Evolution
The main reason, however, that evolution theory cannot provide a full explanation of our origins, is that it can’t take us right back to the beginning of the story. In order for evolutionary processes to get going, a lot of things must already be the case. For example: there must be biological organisms; there must be an environment capable of supporting them; they must be capable of reproduction; random mutations must introduce variety.
How did these things come to be the case? Where did these simple organisms capable of reproduction come from? Why do we have an environment capable of supporting life? Evolution theory cannot provide an answer to these questions, because evolutionary processes cannot occur until these conditions are met. Evolution theory therefore cannot provide a full explanation of the origins of life.
This makes it possible to reformulate the argument from design in a way that renders it immune to evolutionary critiques, making the question of whether evolution theory is plausible irrelevant to the question as to whether design arguments are successful. Modern design arguments begin not with biology and the marks as design in biological organisms, but with physics and the way in which the laws of nature are fine-tuned to make life possible.
The are many marks of intelligent design in the laws of nature. The various physical constants such as the weak force and the strong force must have very specific values in order for life to be possible; they do. The Big Bang, if that is how the universe began, had to involve a very specific amount of energy in order for life to be possible; if it happened, then it did involve that amount of energy. These and other features of the universe make it appear that it was designed with life in mind.
Evolution theory simply cannot explain why we have a universe that is fine-tuned to support life, because the laws of nature have not evolved. The argument from design therefore survives the evolutionary critique; evolution cannot explain our origins.