Debate Post-Mortem

Last Saturday I did my first on-line debate in four years with a YouTuber who goes by the handle MadeByJimBob (who I will refer to simply as JB since JimBob is not actually his real name and MadeByJimBob is just too long).  The topic was "Is Evolution a Reasonable Position?"  The topic was originally going to be "Evolution on Trial" but I pushed back on that for two reasons.  First, that title had the tacit implication that evolution has been accused of a crime, and second, that the actual substance of the debate would be whether or not evolution is true.  I believe it is true, but I'm not a biologist, so I'm not qualified to defend its truth.  The best I can do is defer to the experts.  What I was willing to do was argue for why I think it is reasonable to defer to the experts in this case.

I can save you the trouble of watching the debate by telling you that JB was constantly interrupting me and, hypocritically, petulantly whining whenever I interrupted him in return.  I didn't want the debate to turn into a shouting match, so I just tried to explain that the questions he was asking could not be answered in a six-word sound bite, and if he actually wanted to hear the answers he would have to stop interrupting me while I was trying to give them to him, but it didn't help much.  So there wasn't much substance.  It was mainly JB asking me questions, interrupting me when I tried to answer, and then shaking his head and condescendingly repeating my name over and over and over.  In his world I guess talking over your opponent counts as a win.

There are two things I could have done better.  One was to put more emphasis on the distinction between defending evolution as a reasonable belief and defending it as the truth.  These are not the same.  There are times when it is reasonable to believe things that aren't true.  The best example of this is the belief that gravity is a force that pulls objects towards the surface of the earth.  That is false, but nonetheless reasonable.

The second thing I should have been better prepared for was to explain why my deference to biologists was not an example of the appeal-to-authority fallacy.  Appeal-to-authority can be fallacious, but it is not necessarily so.  Distinguishing fallacious from non-fallacious appeals to authority is a little tricky, but the best way to do it is to go back to the core tenet of the scientific method: find the best explanation that accounts for all of your observations.  In this case, my observations include the uncontested fact that there are over 100,000 biologists in the U.S. alone, and an overwhelming majority (like 99%) of them agree that evolution is true, which is to say, that all of the diversity of life on earth can be accounted for by naturalistic processes, specifically, random variation and natural selection from a single universal common ancestor.  We can also observe that this community produces a lot of useful products, like antibiotics and vaccines, which is best explained by the hypothesis that they have some contact with reality.

Against this we have a community of creationists who insist that life descended from more than one "kind" but who cannot agree on how many different "kinds" there are.  And it's even worse than that.  It's not that there is an actual dispute over what the number is, it's that none of them will even offer a guess as to what the number is.  [UPDATE: turns out that is not true.]  On top of that, this community has never produced anything of value.  Given all that, it's reasonable for an amateur like me to defer to the judgement of biologists.  They may be wrong, but there is quite a bit of evidence that they are closer to the truth than creationists are.

I was taken aback, however, by a critique from another redditor who goes by DarwinZDF42.  [NOTE: I previously said that this person was Dave Farina a.k.a. Professor Dave.  I got this wrong. DarwinZDF42 is actually someone else.  I apologize to Professor Dave.]

Now, I am about to publicly shame DarwinZDF42.  This is something I hardly ever do.  I don't generally think it's constructive to publicly shame individuals.  And I tried to explain to him in the relative privacy of the creation subreddit why he was wrong, but his response was so dismissive and, frankly, obnoxious that I feel this is warranted.  DarwinZDF42 holds himself out as an expert in public, and so I think it is justified to call out his manifest ignorance in public.

The issue at hand is a question I was asked during the Q&A of the debate: what would falsify evolution?  It's a fair question.  One of the classic criteria for a hypothesis to even be considered as a valid scientific explanation is for it to be falsifiable.  The glib answer of "rabbits in the precambrian" refers to an alleged but unconfirmed quote from legendary biologist J.B.S. Haldane as an answer to that question.  Because there is no original source for the quote, there is no way to put it in context, and so we have to make an educated guess as to what it actually means.  And my educated guess is that it means: if we were to find a rabbit in the precambrian era, that would falsify evolution.

That is wrong.  To see that it is wrong, imagine that I went to DarwinZDF42 and told him that I had found a rabbit in the precambrian era.  What do you think his response would be?  Would he immediately concede that evolution has been falsified, or would he be more likely to tell me that I am full of shit, that there is absolutely no way that there could possibly be rabbits in the precambrian, and so I must be wrong?

Now, on this point I would actually agree with DarwinZDF42.  That would be my reaction to someone making this claim.  It is overwhelmingly likely that the person making the claim is lying or has been deceived, and whatever evidence they think they have that there were rabbits in the precambrian almost certainly has a much more prosaic explanation.  But that is irrelevant to the question of whether this would actually falsify evolution.  To answer that question we have to suspend disbelief and consider a counterfactual world where there is actually persuasive evidence of rabbits in the precambrian.  Would that falsify evolution?

No, it would not (though there is a very small caveat which I will get to in a moment).

To understand why, and to understand the "small caveat", I have to start by pointing out that the word "evolution" actually refers to two different (though related) theories.  The first consists of the following general observations:

1.  There are things in nature that make copies of themselves, i.e. replicators exist.

2.  The copies that replicators make are not always perfect.  There is variation.

3.  Some variants of replicators are better at making copies than others.

4.  Which variants are better at making copies depends to some extent on the environment the replicator finds itself in and the variants it has to compete with.

5.  There is a large variety of different environments on earth, and so you naturally get a large variety of replicators.

Those observations lead to a conjecture: that 1-5 are a sufficient explanation to account for all of the variety of life on earth, and that it all descended from a single common ancestor.  No designer is necessary.

Notice that all of this seems plausible even before we look at any actual data.  As framed above, it is a theory that does not require any fossils or trips to the Galapagos.  Democritus could have come up with it.  (In fact, had Democritus actually considered this problem, he may well have even predicted the existence of cells the same way that he predicted the existence of atoms!)

The second thing referred to by "evolution" is a very detailed historical reconstruction of how the current repertoire of life on earth actually arose.  That, of course, is impossible without actual data, and it is bound to be complex, messy, and incomplete, constantly being refined and revised as new data comes in.  Until we have unearthed the last fossil on the planet, this will be a work in progress.

A cornerstone of this historical reconstruction is the so-called Cambrian explosion, a period of very rapid creation of new species.  The Cambrian explosion began about 540 million years ago (MYA) and was followed by the Devonian period (420 MYA) when the first land animals appeared, the Mesozoic (256 MYA) a.k.a. the dinosaur era, and the Paleogene (66 MYA) when the dinosaurs got wiped out and opened the door for mammals to become the dominant land animals.  The earliest known rabbits appeared about 55 MYA.  (And of course all of this is an extreme oversimplification.  There is a reason people make their living studying this stuff.)

So finding a rabbit in the precambrian would certainly be remarkable.  It would be out of place by a few hundred million years, which would surely cause a major upheaval and revision of the currently accepted timeline.  It would probably be the biggest such revision ever.  But would it falsify evolution?  Would it cause the scientific consensus to suddenly accept young-earth creationism?

Almost certainly not.  I can think of many more plausible explanations.  A hoax.  A local event that somehow transported a rabbit fossil into a precambrian geological layer.  A previously unknown geological phenomenon that somehow produced something that looks like a rabbit fossil but actually isn't.  Or even an entirely new and previously unknown period in earth's evolutionary history, the evidence of which is mostly lost to subduction.

Note that that last possibility could plausibly be considered "falsifying evolution" but only in a very narrow sense.  It would falsify part of the current reconstruction of earth's past.  A big part to be sure, but still, only part.  But it would not falsify the central tenet of evolution, that all of life can be accounted for by naturalistic processes proceeding from a single universal common ancestor.  Which is to say, it would (almost certainly) not falsify evolution in the sense intended by the person who asked the question.

So to the question of what would falsify evolution, the glib response "rabbits in the precambrian" is at best just barely defensible, and at worst flat-out wrong (which is one reason to doubt that Haldane ever actually said it, or if he did say it, that he actually meant it, because he was probably smarter than that).  Under no circumstances is it justifiable to berate someone for failing to offer it in response.  That is wrong on so many levels.  Even if rabbits-in-the-precambrian were defensible, there is no excuse for someone who holds themselves out as a science educator to use the condescending and dismissive tone that DarwinZDF42 used with me.  That is never the way to win hearts and minds.  With people like DarwinZDF42 on our side, it's little wonder that the war on misinformation is being lost.