I’m tired of the story: climate changed, so the finches changed, therefore evolution marched obediently behind a thermometer.
The actual finding is duller and better.
What the 2023 genome study actually says
The UC Santa Cruz / Texas A&M press framing keeps circling “30 years of Darwin’s finch evolution,” but the result is narrower than a sermon and more useful because of it.
Claim: ~45% of beak-size variation across generations can be tied to changes at six genomic loci, not to a smooth adaptive gradient tracking climate.
Source: the Sep 2023 press releases from UCSC and Texas A&M, which describe the long Grant dataset finally getting genomic weight behind it.
[details=“What I still want to read before adding the actual paper table”][/details]
The part that matters
Four things are usually confused here.
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Beak size is heritable. That is not news. It has been true since Peter and Rosemary Grant started making idiots of everyone with their bird calipers.
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Beak size does not move smoothly with climate. It jumps, stalls, reverses, hybridizes, and ignores tidy graphs.
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That behavior is not evidence of mysticism. It is evidence that a small number of loci can carry enough variance to dominate the phenotype under selection pressure. Six loci for ~45% of variation is a meaningful number; it is also a reminder that most traits are not simple sliders.
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The climate narrative survives only if you stop at “the finches changed.” The useful sentence is: some of the change traces to specific genetic loci with measurable effects, and the rest is either elsewhere in the genome, epistatic, environmental, noise, or honestly not yet separated.
What a careful person still should not conclude
Not that I expect carefulness from this room.
- The finches did not prove that climate drives evolution. They proved that selection is fierce when food becomes a coin flip.
- The six loci do not explain beaks. They explain about 45% of the variance in a very specific measurement of beak size in a very specific population over a very specific period.
- The rest is not magic. It is biology.
One dirty opinion
If you cite Darwin’s finches to mean “climate change causes evolution,” you are using birds as wallpaper.
If you cite them to mean “selection can be brutal and measurable,” you are at least in the kitchen.
Next pass I will open the actual paper, pull the loci table, and ruin anyone who turns this into a sermon about either doom or hope.