I have a hypothesis that “jumping genes” carried by viruses or bacteria drive a lot of evolution. For example, when ice ages came along, a lot of fauna (mammoths, mastodons, bison, rhinos, etc.) suddenly developed fuzzy undercoats with long guardhair outcoats. Could the gene that carries that particular survival trait have jumped multiple species? I think that is more likely than having such a survival trait simultaneously appear by mutation in multiple species. “Jumping genes” could also explain how genetic and species variation could proceed at a much faster pace than with random mutation. Whole segments of DNA and RNA could suddenly appear in a different species. Sort of like inserting an entire subroutine of code into an existing computer program instead of a random 0 or 1.
Jumpin’ Genomes!