As a promoter of science literacy and therefore the theory of evolution, I often get some push back from those who are either unaware of the tenets of the theory, or are straight up opposed to it.
One of the most common arguments is to say that evolution is impossible, because evolving something as complex as the human eye, for example, would be “like a tornado going through a junkyard and creating a 747.” This is meant to imply that creating a complex structure is impossible by chance, and therefore that there had to be some “intelligent design” to the process.
Of course, this does sound like a serious claim if you have never learned the ins and outs of evolutionary theory, but just a brief introduction to evolution could sort this fallacy out.
Fixing the Fallacy
So the “tornado in a junkyard” fallacy assumes that 1) evolution works completely randomly (like an indiscriminate tornado whipping about various parts), 2) that the evolution of a complex biology happens all at once, and 3) that probabilities are against the whole theory. Let’s take each point in order:
1. We could put this first part of the fallacy definitively to bed. One of the main aspects of evolution is that it is certainly not random. Via fellow skeptic Donald Prothero:
Evolution is not “random chance” like a lottery or throwing the dice. The variation on which natural selection works (mutations, recombination, etc.) is randomly produced, but natural selection is not random. Natural selection is a process that weeds out unfavorable variations, and greatly improves the likelihood of events.
Creationists also use another analogy similar to the “tornado in a junkyard” fallacy when they claim that evolution would be like having a bunch of chimps hitting keys on a typewriter and coming up with Shakespeare. But evolution does not simply pick through random mutations and has something complex then pop out. Natural selection in this example would pick the beneficial keys (as it does for mutations) each time a random key is hit, making the process a lot faster, and easier to grasp. Using a correct chimp-based analogy, evolution is like producing one of Shakespeare’s plays by hitting trillions of random keys and selecting the letters that are in the right order as time goes on. In fact, the process has been attempted via computer program:
Evolutionary biologist Richard Dawkins employs the typing monkey concept in his book The Blind Watchmaker to demonstrate the ability of natural selection to produce biological complexity out of random mutations. In a simulation experiment Dawkins has his weasel program produce the Hamlet phrase METHINKS IT IS LIKE A WEASEL, starting from a randomly typed parent, by “breeding” subsequent generations and always choosing the closest match from progeny that are copies of the parent, with random mutations. The chance of the target phrase appearing in a single step is extremely small, yet Dawkins showed that it could be produced rapidly (in about 40 generations) using cumulative selection of phrases. The random choices furnish raw material, while cumulative selection imparts information. As Dawkins acknowledges, however, the weasel program is an imperfect analogy for evolution, as “offspring” phrases were selected “according to the criterion of resemblance to a distant ideal target.” In contrast, Dawkins affirms, evolution has no long-term plans and does not progress toward some distant goal (emphasis mine) (such as humans). The weasel program is instead meant to illustrate the difference between nonrandom cumulative selection, and random single-step selection. In terms of the typing monkey analogy, this means that Romeo and Juliet could be produced relatively quickly if placed under the constraints of a nonrandom, Darwinian-type selection, by freezing in place any letters that happened to match the target text, and making that the template for the next generation of typing monkeys (emphasis mine).
It always seems odd to me that those who are so against evolutionary theory know so little about it. If you would just read how it is normally presented “evolution by natural selection” it becomes clear that evolution is not at all random. Sure, it works off random mutations in DNA, but the selection of those mutations is not chance.
What this means for the “tornado in a junkyard” fallacy is that the underlying premise of the analogy is incorrect. Evolution is not random. Having a tornado that selects the right pieces in the right order over millions of years would be a more apt description.
2. The fallacy assumes that evolution means producing something complex like an eye or a heart in just one step and is therefore too improbable. I would agree that this would seem too improbable if evolution actually implied this, but it does not. Evolution, the selection of random beneficial mutations over millions of years, works through innumerable intermediate steps between something simple and something complex. A genetic mutation is not an unlikely event, but producing a fully formed eye in one go is. However, if we follow evolutionary theory and follow the intermediate steps, something complex emerges from something simple, with no step along the way being too improbable.
If you look back on the development of some trait and add together all the small probabilities, it surely seems hard to get from simple to complex, but if you follow each step along the way, we find that it is completely within the realm of possibility.
Bringing this back to the fallacy at hand, this would mean that for the “junkyard” analogy to be a correct one, it would have to include a tornado which at first gathers only a few pieces of junk in a beneficially selected way, over time making small and incremental improvements on the simple beginnings. This makes the process of evolution much easier to grasp from a probability standpoint, and is in fact how evolution works.
3. Finally, those who argue against the probabilities of evolution are perpetrating yet another fallacy. Again via Donald Prothero:
As anyone who really understands probability knows, you can’t make a probability argument after the fact. If you do so, then any complex sequence of events is extremely improbable, even though they actually occur.
For example, imagine all of the various events that had to occur for you to be reading this post. You had to be born to the right parents, in the right time period, have the necessary interests based on genetic and environmental factors you do not control, speak English, not die from any of the various hazards of the universe, etc. Looking back on this after the fact makes the idea of you reading this post seem impossibly unlikely to have occurred. Yet it did occur. That is the point. Just because you cannot fathom how something got to where it was probability wise does not mean that it could not happen (keeping in mind that it did in fact happen). Arguing in this way misunderstands probability and further confuses any discussion of evolution.
The “tornado in a junkyard” fallacy is one of the most common arguments against evolutionary theory. However, as I have tried to explain, it is a false analogy on all points. Evolution is not random, it does not work through one impossible step to produce something complicated, and you cannot argue probabilities after the fact to make a case.
I hope that this settles things a bit for those of you who have not heard of this fallacy or need some ammunition to fight against it. Though completely discredited, sadly, I think you will being needing it.
[With help from Skepticblog]