The Language of God, Chapter 5
By B.J. Marshall
Before tackling the gritty details using DNA evidence to support human evolution, Collins addresses Darwin, mutations, and the “rather arbitrary” distinction between microevolution (“incremental changes within a species”) and macroevolution (“major changes in species”) (p.131-2). In my discussions with Creationists, the micro- v. macro-evolution thing always comes up. So I was pretty excited to see how Collins would cover this topic.
He does a fairly decent job mentioning how we’ve seen lots of changes within species, such as finch beaks changing shape over time. He also discusses saltwater v. freshwater sticklebacks and rapid variation in viruses. He even brings stickleback evolution into a DNA setting by stating that the specific gene – EDA – has repeatedly and independently appeared in freshwater, resulting in sticklebacks losing their plates. Oh, but it gets better, because humans also have an EDA gene, and “spontaneous mutations in that gene result in defects in hair, teeth, sweat glands, and bone” (p.132). So, Collins adds as he tries to connect sticklebacks to humans, it’s not tough to see how the differences between sticklebacks could be extended; “larger changes that result in new species are a result of a succession of smaller incremental steps” (p.132). And that’s fine for highlighting “microevolution,” which is something Creationists can believe anyway. And it’s even good for alluding to macroevolution given his “succession of smaller incremental steps.” But he only ever leaves it at the hypothetical.
He does his readers a disservice when he claims “we haven’t seen new species arise” without expanding on what speciation is (p. 132). Additionally, he leaves the door open to Creationists by saying macroevolution only consists of “major changes” in species. Speciation is kind of a vague line but is usually delimited by two species’ ability to interbreed; they usually can’t or, if they do, their male offspring are sterile. And the fact is that we have observed speciation in a number of instances. One example is in polyploidy organisms that contain a multiple or combination of complete genomes; these usually result in new organisms that, due to the number of chromosomes, can’t reproduce with their originating species. It’s called allopolyploidy if genome duplication happens through crossing two different species. Another way speciation can occur is through sexual isolation, such as in ring species such as the Ensatina eschscholtzi salamander.
But, regardless of whether we’ve observed speciation, Collins gives Creationists a foothold by leaving it up to interpretting what constitutes “major changes” in species. For example, perhaps the inability to breed isn’t too bad, because all those salamanders still look very salamandery. It’s not like you get a crocodile and a duck together!
Other posts in this series: