Evolution Explained, Part 3: Facts and Proof

[This is Part 3 of a series of approximately sixty posts that outline evidence, support, and explanation for naturalistic evolution. To receive notification of further posts and for all posts from Dennis Mitton please select the Follow button at the top right of any page. Please comment and please enjoy!]
Copyright 2020, Dennis Mitton


Shrug SignCan’t Prove It

It surprises people when I say that, “No, I can’t prove it to you. Science is not in the proving business.” Creationists laugh like hyenas. “See? He can’t prove it! What a dolt!” Then I ask them to prove that Omaha, Nebraska, exists and they are stumped and offer no proof or anything even near to a proof. They didn’t expect that one. Let’s get is straight: there are no proofs in science. We have facts, and we have assertions. Proof is the milieu of philosophy. So, funneling ideas and observations down, we have facts, proof, and assertions. Let’s look at the three.


Facts are indisputable observations that exist independently of the observer. I say indisputable, but you know where this goes: everything is up for debate. My writing desk is made of Honduran mahogany. Hearts pump blood. These are facts. Facts usually make up the premises of arguments, the things that both parties can agree on, and they are the components of scientific hypotheses and theories. But facts are not proof and are always subject to tweaking.


Proof is the least useful of the terms. Its technical use is in philosophical logic, where it is the conclusion to a set of premises:

Sally is a mammal.
All mammals have hair.
Sally has hair.

If the premises – the first two statements above – are true, then the conclusion must be true and, according to this metric, you have proved your point. But technical proofs don’t have to reflect the real world:

Sally is a gold coin.
All gold coins have green skin.
Sally has green skin.

Here the proof logically follows the premises, but it’s pure goofiness; made up silly business. So here, at least academically, there’s a limit to logic.

While it’s difficult to prove a thing to be true, it’s harder to prove it false. It is possible – and I can’t prove it to be otherwise – that I am a brain in a vat and my entire life experience is programmed by pizza-eating teenagers from the planet Zoltar. Technical or absolute proof does us no good here. From Part 2 we read this from the National Center for Science Education regarding theory and proof:

“[Another] misconception is that scientific research provides proof in the sense of attaining the absolute truth. Scientific knowledge is always tentative and subject to revision should new evidence come to light.”

You figure it out while I float here quietly.

It Has to be True. I Say So: Assertions

Conversations in science and life are really made up of assertions which are statements we make with varying levels of confidence. Much of our conversation is spent shoring up confidence in our statements. We might say “Now, I’m not lying here” or “I’m not making this up, but…” These are verbal codes that lend an air of confidence in what we are saying. Technical talk has its own set of confidence codes. A journal abstract is a kind of academic code for “I’m not making this stuff up.” They list the universal nature of the finding (We tested 400 males aged 20-40 from 13 countries…), they set out the known and agreed upon facts (based on Major’s paper from 2008 we know that…), they make a prediction (we intend to show that…), and they tell their story (we find that…). In this way, researchers build a staircase of step wise assertions that must, by logical progression, lead to their conclusion making a path from A to Z.

Some statements elicit more confidence than others. Only a few high-school philosophers will argue with me when I say that the sun will rise tomorrow. Everyone, everywhere, for all of history has seen the morning sun come each day. There is no reason to doubt that it will tomorrow. We have great confidence in the assertion. That the sky will be blue tomorrow is less so. The sky could be overcast or pour rain all day. If it’s December in New York, and I’m predicting eighty and sunny tomorrow – statistically possible – then I’ll be looking hard for takers.

Facts, Assertions, Proof – They All Work Together

This is exactly how science and evolution work. We look at facts and put together an overarching explanation based on observation. (See Part 2 for an explanation of a scientific theory.) From there me make predictions. We believe that mammals appeared on earth after reptiles because we don’t find mammal fossils embedded in rock strata older than where we find reptiles. Both radiometric data and comparative biology support this finding. Each time we find another example, we are more confident in our assertion. This entire framework is vetted over decades of work from people in several disciplines, and we come to recognize the fact that reptiles appeared on earth before mammals. This is exactly how the concepts of quantum theory, germ theory, and evolutionary theory have developed.

It can be messy. This jumble of descriptions, facts, proofs, and assertions are exactly why we use specific descriptive terms. For example, one definition of species might be ‘a genetically isolated reproducing population’ which is much the same as ‘like animals having sex’ but the first description contains a ream of tacit background information that the second doesn’t. This language isn’t used to sound smart or to confuse people (which is a common charge not always wrong). It’s a way to put a fence around a statement and pack as much information into it as we can. It’s a way, too, to define what we are not saying. Biology is rarely a black and white endeavor. Some people hate this. If you find exceptions to the rule bothersome, I suggest a career in chemistry or engineering. Those are sciences of yes or no, of black and white. There are exceptions to every statement in biology and this argues for evolution. All life and every ecosystem is in flux. Every genome is different and changing. Every ecosystem is different this year than it was the year before.

Hang whatever seal or college or church symbol you want. I find that the harder the top is hit, the more the banger is trying to convince you of something even they don’t believe.

A Possibly Wrong Parenthetical Observation

I find science-minded folk to be the most comfortable with not knowing. It’s the milieu in which science works. Once a thing is figured out, the next question is always why? Researchers push against the boundary of what is known to extend into what is not. This is the exact opposite mindset of many religious people. Well, at least of the most vocal Christian conservative evangelicals. To them, not knowing is anathema: it’s uncomfortable to the point that some people ‘believe’ just to fill in the gap. I can’t say how many people I’ve run into who shake their heads when I shrug my shoulders at how I can live with not knowing what existed before the Big Bang. I just don’t know. I doubt that we will never know. We are just bags of wet carbon, after all, and no one owes us an answer. But certain people simply cannot live with that anti-answer. It’s weird to me.

And finally, remember, like I mentioned previously, we might all be brains in vats so have a little humility and hold your most dear beliefs a bit more loosely.

Arguments Against

People argue that we cannot determine prehistoric fact, which relegates evolution to a guessing game. But is it a fact that Abraham Lincoln was a US president? And that he was shot? How do we know? Not a soul is alive today who was alive in Lincoln’s time. We know by correlating evidence. We read the DC newspaper at the time he was shot. Was this corroborated in any Paris newspapers? We see Lincoln’s grave. We make a prediction: if Lincoln was shot and killed, we should see another person sworn in as US president shortly after Lincoln’s purported date of death. We find that this is true. These historical tools we use are the same we use for prehistoric findings and give us the same level of confidence. Evidence leads to a hypothesis from which we develop predictions which bolsters or changes our hypothesis. Natch!

Evolution is also sometimes dismissed as an invention. “You can make up whatever facts you want.” No, you can’t. Facts exist regardless of who looks at them. You can make up whatever truth you want and you can certainly have whatever opinion you want, but you can’t make up facts. This is closely followed by the statement that we all have our own truth. Again, I agree. You get to make up your own truth. But you don’t get to make up your own facts. Facts, as described above, exist independent of the observer. You can interpret how a fact fits into your worldview but, as they say, the facts remain.

Science and Religion

What is the difference between a scientific fact and a religious fact? Aren’t they the same thing? No, and there are two keys to understand: source and objectivity. On my desk is a piece of fool’s gold. We can look up the geological definition if we want and I’ll guess that the clump weighs fifty grams. These are observations that exist apart from me, the observer. Each observation can be verified by anyone with the right tools who knows how to use them. So, here is a fact, and its source is empirical. Contrast this with a religious statement: Jesus can save you from drug addiction. It’s true that many people quit using drugs when they become a Christian. It’s just as true that many non-Christians quit using drugs. It’s also true that many Christians use drugs. There is simply no way to measure this statement. And how would you set up an experiment to test your theory that Jesus can save from drug addiction? How would you isolate the variable? And however strongly you believe the statement to be true, I can find ten people who disagree with you. These statements simply don’t approach the rigors of fact and scientific inquiry and are mere opinions. I’m not saying there is no religious fact, just that it is not a scientific fact.

Come back for the next post when we will look at the most powerful tool for good ever invented – the scientific method.

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