I’ve belabored this issue before, but there’s always a new crop of readers who might need a lesson. I’m talking about a common creationist trope: the claim that microevolution can occur, usually defined as “evolution within a species” or “evolution within a kind” (whatever a “kind” is), but that macroevolution—seen as a transition from one “kind” to another—doesn’t occur. So antibiotic resistance in a bacterial species, or a change in coat color of a mouse, is fine, because that’s just “microevolutionary change”. Ditto with the evolution of different species of cats, which is simply microevolution within the “cat kind.” And ditto for the creation of different breeds of dogs by artificial selection: breeds so different that, if they were found as fossil skeletons, some would be seen not just as different species, but as different genera. Nevertheless, creationists see that as simply change within the canid “kind”, so that artificial selection is mute about the possibility of macroevolution.
This, of course, is bullshit. Even creationists—those who lie for Jesus—are surely aware of the pervasive empirical evidence for macroevolution. Much of it is outlined in my book, including embryological development, the fossil record, and dead genes. All of these testify to a distant evolutionary kinship between members of different “kinds”. We have, for example, transitional forms between fish and amphibians, amphibians and reptiles, reptiles and birds, reptiles and mammals, and, of course, early ape-y ancestors and modern humans (to a creationist, Homo must always be its own “kind”). And those transitional forms just happen to occur at the proper time in the fossil record. Mammal-like reptiles, the transitional forms between reptiles and early mammals, occur in the sediments after reptiles were already around for a while, but before easily recognizable mammals come on the scene. It’s not just that they look intermediate, but that they lived at the right time for demonstrating a true evolutionary transition. (A “mammal like reptile” that lived 500 million years ago wouldn’t prove anything.)
“Dead genes” (stretches of DNA that don’t produce a product, but are largely identical to working genes in relatives) are likewise evidence for distant ancestry between “kinds.” Why do humans have three dead genes for egg-yolk proteins—just the proteins still produced by our reptilian and avian relatives? Why do cetaceans like whales have hundreds of dead olfactory-receptor genes? Those genes testify to a terrestrial origin of whales, with the sniffer genes no longer needed for a life underwater. That, too, shows macroevolution, for surely a whale and a deer are different “kinds.”
And of course there’s no theoretical or empirical reason we know of that sets limits to how much evolution can change plants or animals—yet such limits would have to exist to allow microevolution but not macroevolution.
So for both theoretical and empirical reasons, we can reject the macro/micro difference so beloved of creationists.
These two tweets show the theoretical weakness of the creationist argument, with “First Clown,” who defends evolution regularly on his/her Twitter site, taking down the “no macroevolution” argument in a nice way: