Evidence for Evolution - Your Elevator Pitch

A friend asked me the other day why I accepted evolution. Essentially he was asking what the evidence was.

As a starting point, let’s assume we agree on an old earth (4 Billions years or so).

I know we have consilience between the age of fossils and phylogenetic trees. What else you you describe as the strongest evidence for evolution?

Here is my pitch: Livestream: How I Changed My Mind on Evolution .

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For me the strongest selling point is the consilience of so many independent lines of evidence. The geologic data agrees with the radiometric dating data which agrees with the fossil phylogenetic tree which agrees with the genetic phylogeny. It’s one big coherent, corroborating and cross-correlating picture from millions of little pieces.


The nested hierarchy. There is absolutely no reason why design or separate creations should produce a nested hierarchy. Buildings, art, cars, computers, and even computer code don’t form nested hierarchies. The only process we know of that will necessarily produce this pattern of similarities and differences is evolution.


Special creation progressively by modification of existing species would produce nested clades…

I modify existing species and I regularly violate a nested hierarchy. I currently have a plasmid for insertion into human kidney cells that contains a firefly gene and a jellyfish gene (luciferase and green fluorescent protein, respectively). There is no reason why a designer could not incorporate designs from other lineages when modifying existing species.

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A designer might no do that on a regular basis.

But I agree that nested clades indicate common descent. I’m just pressing back on the idea that it negates any and all understandings of special creation. It doesn’t:

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You will notice that I am careful to say that a nested hierarchy is not expected from ID/creationism while it is expected from evolutionary processes. Throw in a few mentions of parsimony for good measure.


No piece of evidence will ever negate any and all possible permutations of special creation, so that isn’t and has never been anyone’s goal.


Thanks, but that’s a long elevator ride.

If I was to try and summarize, would I be correct to say that the fact genetic diversity isn’t correlated to functional differences, but instead to models based on common ancestry is the evidence for evolution?


True, a creator that basically causes evolution to happen would produce the same evidence as just evolution. The evidence for evolution isn’t supposed to be impossible to fake.


I think this is what I’m trying to better understand. So a couple of questions.

Am I correct that agreement of the geologic data with the radiometric dating data gives us confidence in dating of fossils and the (and other geological changes), but doesn’t really provide evidence of biological evolution?

However agreement of these dates with the fossil phylogenetic tree and it’s agreement with the genetic phylogeny provides evidence through consilience of these different evidence?

However this creates another question. How is the fossil phylogenetic tree generated?

Am I correct in assuming genetic phylogeny is the tree generated by looking at the genetic changes between organisms and what we know about mutation rates?

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What he said. That’s the strongest evidence. I’d say, however, that the most obvious evidence, which is rather different, would be the biotic succession of the fossil record. That is, the earliest biota is very different from the current one, and successive biotas become more and more like the current one.


That’s my second favorite.


Well, this is a hopeless task, since it is not actually reasonable to explain evolution in an “elevator pitch.” But one thing I typically emphasize is this: evolution has been observed and measured and dissected and tweaked and then observed and measured again. Guppies. Teosinte and so many other plants. Yeast and bacteria in giant experiments. Finches and anoles. It’s actually not even sane to ask whether there is “evidence for evolution.”

The question “what is the evidence for evolution” then becomes “what is the evidence that evolution has been happening continuously since the beginning of life?” which is suddenly a different question. Then we can talk about fossils and change over eons and so on.


I’m a little nervous at the implication of progress from simple to complex. Are lizards really more complex than trilobites? By what measure? I would prefer to say there’s been a progression from the a radically different biota to the modern one. No trilobites now, no lizards then. And so on.


It’s created in the same way that trees of extant taxa are created: by coding the characteristics of the taxa into a taxon x character matrix and then examining a large number of potential trees using some algorithm that evaluate the fit of data to tree, choosing the tree with the best fit. (Bayesian methods work somewhat differently, but the result is similar.) The main point here is that stratigraphic position is not used to evaluate trees.

No. Mutation rates are not relevant per se, though the relative rates of different sorts of mutations, e.g. transitions and transversions, are. Most methods require an explicit model of evolution, with the relative rates of various mutations included as parameters.

It would in fact be indistinguishable from common descent in all respects, as long as the modifications were small tweaks. But this would seem to be not special creation but a form of guided evolution. Having slightly modified species poof into existence rather than being modified in situ would be an extremely odd way to work.


You’ve jumped over my head, so let me try to restate this as I understand it to see if I’ve got it right.

We identify a set of characteristics that fossils have. I’m guessing, but this might be the pattern of bones, length of certain features, etc. We then feed this information into tree finding algorithms to determine the best fit given all of the data we have.

Have I got that close to correct?

Island biogeography.

E.g. lemurs on Madagascar, marsupials in Australia, red squirrels in the UK, sloths and oposums in South America, and birds on New Zealand, the Galapagos, Reunion, Hawaiian islands, Madagascar,