Bird backpacks demonstrate Darwin’s first postulate of Natural Selection

23 Apr

It takes a while to recognize differences among individual organisms of the same species. We all intuit them about humans, but our picture books teach us as kids that a fish is a fish is a fish. Add the fact that these differences fall into three classes, and it’s a lot to take in.

Once this appreciation sinks in, it becomes difficult to see even how twins can be truly identical. Among all those base pairs in the genome, some unruly A has to have swapped out to C. And the thing I love about Natural Selection is that it’s a beautiful syllogism: once you grasp three premises, the proposition is just there.

More than anything else in our paved paradises we encounter differences among automobiles, observing very small sample sizes of living organisms. It always jolts me out of my assumptions when I see students have ah-ha moments with the first postulate of individual variation. For a teacher struggling to grasp why students struggle to grasp selection, smacking into the gap between what students are assumed to know and what they don’t know is humbling but refreshing. I am increasingly finding that nature, not technology, is instrumental in biology classrooms. It is ridiculous to rely solely on students transferring their knowledge of mutation to individual variation. How easily do I transfer the abstract and microscopic to the warm and soft?

So, here’s a nice study of the individual differences in pigeon behavior, measured–essentially–with “critter cams”. I’ve linked below to a 3 minute news radio report summarizing the rationale and findings.

It’s not trivial that Darwin and Wallace arrived at their famous syllogism during years of sleeping under the stars, trying to avoid sleeping with the fishes. Naturalists (and profiteers) in England were great collectors, and inherent to collecting is individual variation. As James Audobon said, “When the bird and the book disagree, always believe the bird.”

NPR: Backpacked Birds Reveal Who’s The Boss


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