The authors offer a selectionist explanation, which is nevertheless uncertain. Note the repeated use of the subjunctive.
This is by no means an all-or-nothing selection (as the impression is sometimes given). Rather, the alleles are retained.
Scientific data are followed by the myth: “Finch beak morphology observed on the Galápagos Islands was used by Darwin to formulate his theory of evolution.”
How could the authors suddenly do this? Some of the following points may be considered.
In a series of posts starting today, I offer some notes on the question of whether macroevolution is happening on the Galápagos Islands.