God hates shrimp – part 2

Last week, inspired by this shrimp tale, we talked about scientific theories (AKA models that explain observations) and showed how Darwin’s Theory of Evolution, updated via DNA, is a good description of what we see today, and a good enough predictor to use for commercial products that make money, today. What about the past? Is there anything that could disprove the Theory of Evolution as a descriptor of the ancient past? What would it take? Well, based on what we’ve said so far, you’d have to show that its predictions were wrong, or that it contained an irreconcilable internal contradiction, or that your model was better. More to the point, since modern day evolution theory (currently) passes all the tests, you have to show that when it is applied to the past it creates incorrect predictions or logical inconsistencies, or that there is a better model.

The past is a funny place. We can’t really perform experiments there, the kind that John Platt talked about in “Strong Inference“, where you make a hypothesis (untested theory), devise an experiment that will test it, then run the experiment and live by the results. We can’t actually run the experiments we would like, so we do observational science. Let me use Astronomy as an example.

We can’t do experiments with stars — as an SF reader I have to add the disclaimer…yet. Which means our inferential approach has to be that we build models based on lab measurements and create theoretical evidence chains, and then go look to see if we got it right. In Astronomy, we take what we know about thermonuclear reactions – from measurements both in the lab and at various Pacific atolls – and we make some prediction, say that if we pointed our instruments at the sun or some other star we would see X. And we go out and point the instruments and we very often do see X. When we don’t, we say that that hypothesis failed, and we go back to the drawing board and build a new theory.

Sometimes the flow is in the opposite direction — we see some phenomenon in the universe, and we have to come up with theories that explain it. Cosmological red-shift, and the missing-mass, AKA dark matter investigations are but two examples. Helium is another. It was detected in solar spectra before we isolated it on Earth, but the fact that a spectrographic discovery preceeded an chemical one strengthend our confidence in our theories. Often, we can’t say if the hypothesis is correct or not because we can’t make that particular measurement with existing equipment (very common in ground-based pre-space age Astronomy), or because we have not yet found a star that would let us measure X.

Coming back down to the Earth of long ago, our first step is to ask, how long ago? Well, there are a number of nuclear decay processes that produce measurable byproducts at different rates and ratios. Even sixty years ago, our models of nuclear processes were good enough to win a war with (and kick start theoretical astronomy). Nothing since then has challenged that part of our understanding. Geologists have gotten pretty good at dating various rocks. And when you date the rocks, you date the things you find in the rocks. Like fossils.

We see the bones of lots of dead animals buried in the rocks. In general, the older they are, the more they are likely to look different. These differences, when we can check them (for example in the monster fallow deer called the Irish Elk) turn out to be associated with differences in the animals DNA. So we have a probe that can go back maybe 30 thousand years, with luck, and when we are able to use it, it tells us that evolution was working then in the same way it works today. More precisely, the observational measurements we make are consistent with the evolutionary models we developed based on modern biology, in the field and in the lab.

As we move to older and older rocks, we lose our ability to measure the DNA, but we see the animals continuing to change, due to evolutionary changes in the biology. We can see places in the past where suddenly there are almost no fossils of a given age — because, we believe (based on other observations), most of them were killed by volcanoes or ice ages or asteroids — and the fossils after that point are more limited and different from those before. And those different fossils, over time, change and vary and spread into new ecological niches, replacing those that went before, just as evolutionary theory would predict.

OK, so let’s look at disproving the Theory of Evolution as a reliable model of the past. The wrong prediction part is easy. Show, for example, that our theory of nuclear decay (and the ancillary models that gave us transistors, computers, and iPhones) is fundamentally wrong, so that our dating models don’t work.

The logical inconsistency part is harder — because if there were any they would likely have surfaced by now. But the approach is sound. Find me a breakdown in the logic used to apply current knowledge to past events. Why should something that is correct today be incorrect in the past. With history and archaeology it is somewhat easier to define that kind of failing. Usually it is due to an incomplete model — we fail to comprehend the motives of a person or culture because their actions are not in accord with present day Western moral and ethical models, not taking into account that their mores and ethics were different.

Finally, build me a better model. A model based on a totally different mechanism — and tell us what that mechanism was and how it worked and why it stopped working when it did (or how it is still working). Make a prediction, that when we make observation X it will look like this, when conventional theories would say it should look like that. Build me a model that allows DNA-based evolution today but includes some mechanism that was at work earlier and stopped working just at our DNA boundary. Finally, in John Platts words, tell me what evidence it would take to prove your model wrong, and tell me what experiments you have in train to obtain that evidence.

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