Ring Species and the Fallacy of the Discontinuous Mindset
“Species” is not a discontinuous concept, but a fluid one. For example, imagine you’re baking a cake that needs to be baked for 30 minutes. If you took it out at 29 minutes and 59 seconds, it would still be “done”, would it not? The same goes for 29 minutes 58 seconds. However, if you took it out at 10 minutes, it wouldn’t be done. But it’s nearly impossible to pinpoint the second that it becomes “done”. An example of the fluidity of species are special cases known as ring species, where you have a series of subspecies that can interbreed with their neighboring, closely-related subspecies, but the two at the ends of this spectrum cannot breed with each other (see diagram below).
A group of salamanders in California illustrate this point beautifully. At the South end of the Central Valley, you find two very distinct species, Ensatina eschscholtzi and Ensatina croceater. However, as you work your way up and around the Northern tip of the valley, you see a constant blending from one species to the other, and when they meet back up again at the tip, they are two separate species. But a specimen from the Southern part could mate with one from 20 miles further north, as that specimen could mate with another salamander another 20 miles further north, continuing on in an unbroken chain around to the other species back at the origin of this loop.
Another good example is that of herring gulls and lesser black-backed gulls around the arctic circle. Either way, a ring species is showing us spatially what normally happens temporally. These things are often difficult to comprehend with our discontinuous mindset, where a species is a fixed concept. Humans and chimps have a similar strand of gradual continuity between each other, except the intermediates happen to be dead.
These ring species are easy to explain through evolution, but difficult to explain via Intelligent Design (unless we’re assuming the designer wanted to design evidence of evolution). This concept is also directly linked to when a new species “appears”. With the exception of polyploidy, new species never “pop up”. This is known as saltation, and is a direct refutation of evolution. This is why we don’t see things like a chimp giving birth to a human, or Kirk Cameron’s beloved crocoduck.
Instead, over the last six million years there has been a steady progression between a chimp-like ancestor and modern human. There was never one point where “voila!” we have a human. If we could get a time machine, we could transport a modern human back 2000 years, and they would be able to successfully mate with a human of 2000 years ago (biologically… socially this would be quite difficult, and likely rather repulsive considering the relatively recent invention of soap). Likewise, we could take that person of 2000 years ago, and transport them back another 2000 years, where they would be able to successfully mate with a human of 4000 years ago, and on and on back, in the world’s first time travel breeding experiment.
The ring species is excellent evidence for evolution. It’s the kind of thing we expect to find if we think species are evolving. However, assuming a static history of life (as we’d see if life was designed to not evolve), this is completely illogical and antithetical to the concept (unless we counter for some sort of whimsy and mischief on the part of the designer). Of course, if someone has an explanation for this, I’d be more than willing to hear it.