Jon Perry is a filmmaker and science educator who produces educational videos for the YouTube channel Stated Clearly. His main focus is defending and explaining evolution, with an emphasis on persuading “Bible Belt” folks, “creationists,” and “religious people.” See his interview here:

Perry’s videos are clear and easy to watch, handsomely illustrated, relatively jargon-free, and have brought him a wide circle of scientific advisors, including such familiar names as P. Z. Myers, Joanna Masel, Hans Thewissen, Phillip Gingerich, and David Deamer.

That’s background. A recent Twitter thread from Perry is worth a look. As he puts it, Perry is seeking evidence of “single mutations of large phenotypic effect in animals.” The examples provided by his respondents — e.g., loss of structures, changes in coat color — are interesting, Perry allows, but not on point. Then his exchange with biologist Stuart Newman, a “Third Way” evolutionary theorist who doubts neo-Darwinian theory, devolves into rhetorical heat, as you can see below:

Perry is looking for the experimental or observational evidence to corroborate what he thinks the fossil record shows, namely, the rapid origin of anatomical novelties (e.g., bat wings, whale flippers, the Cambrian Explosion of new body plans). The obvious problem? Following the rise of neo-Darwinian orthodoxy in the 1930s, “single mutations of large phenotypic effect” were scorned by the mainstream of evolutionary biology as evidentially unsupported saltationism, and pushed to the periphery of acceptable topics for research. Or beyond that border: Stephen Jay Gould, in his introduction to the 1982 reissue of Richard Goldschimdt’s The Material Basis of Evolution (Yale, 1940) recounted how the very name “Goldschmidt” became a byword and laughing stock for properly trained biologists.

So we wish Perry well in his search for the missing evidence. The fact is, he wouldn’t have to ask around, on Twitter, if that evidence existed. He could just look it up for himself, and/or everyone would already know about the evidence, and there’d be no point in producing the video.

By the way, Newman’s question to Perry — what is the scenario for the origin and diversification of birds — is strikingly similar to the question Goldschmidt asks at the end of the introduction (pp. 6-7) to The Material Basis of Evolution.