Signal + noise = all the observations.
I understand why evolutionary biologists protect their core commitment of universal common descent (UCD). We don’t want our central theories bounced around like a beach ball every time anomalous observations pop up.
On the other hand, when UCD is protected from empirical challenge by moves such as “that’s just noise, and we expect noise,” or an indefinitely elastic ring of auxiliary or ad hoc hypotheses (e.g., incomplete lineage sorting, convergence, horizontal transfer, you name it), UCD looks dangerously like an axiom, not a testable proposition.
“Oh come on, Paul,” you say, “no responsible evolutionary biologist thinks that UCD is an axiom.”
Actually – you’d be surprised:
“As a first principle, we adopt the Darwinian idea that all life is related.”
From here, first sentence of the paper:
“First principle” sounds like an axiom. In my academic life (1980-2018), I’ve watched one prediction of UCD after another – e.g., the universality of the genetic code, the conservation of early metazoan development, the homology concept [i.e., homologous genes underlie homologous anatomy] – go belly-up, and yet UCD largely holds its place as central theory.
Can you see why I’d be troubled? (This has little to do, btw, with my opinions about ID. I’d have the same worries if I were a philosophical naturalist and accepted “evolution,” meaning the natural origin of living things from non-living starting materials, as the best explanation for organismal diversity.)
Here’s a thought experiment, or a poll. What would you expect a leading philosopher of biology and evolutionary theory to say about the widely-accepted prediction, from UCD, that the discovery of a fossil mammal in pre-Cambrian strata would overturn UCD?
Please vote and then I’ll post the answer. Polls close at midnight today (10/31), when my wife and I start to consume the leftover Halloween candy.
