On one of the Galápagos islands whose finches shaped the theories of a young Charles Darwin, biologists have witnessed that elusive moment when a single species splits in two.
Well, that would be very interesting… if it were true. But whenever I’ve heard these finches mentioned, it turns out that what actually happened is that populations of different kinds of finches increase and decrease in response to changing environmental conditions. No finch’s beak actually changes size! Some finches with beaks more adapted to the environmental conditions survive and leave more offspring than other finches who are not as adapted. When conditions change, the changes in populations reverse themselves and return to equilibrium.
The deeper problem with the Wired Science report is not its perpetuation of the legend of Darwin’s finches, but its false claim that biologists have now “witnessed that elusive moment when a single species splits in two.” This is not what Peter and Rosemary Grant reported in their scientific article in the Proceedings of the National Academy of Sciences. 6
According to the Grants, in 1981 they found an unusually large male medium ground finch (scientific name: G. fortis) on the island of Daphne Major that they labeled 5110. They inferred that it had probably immigrated from the nearby island of Santa Cruz—though they could not be certain. For 28 years, the Grants followed all known descendants of this presumed immigrant, and genetic analysis suggested that after 2002 the descendants of 5110 bred only with each other (and were thus “endogamous”). The inbred group had a distinctive song that may have contributed to its reproductive isolation from other medium ground finches that were in the same area (“sympatric”).
But the Grants did not go so far as to label the inbred descendants a new species. “We treat the endogamous group as an incipient species because it has been reproductively isolated from sympatric G. fortis for three generations and possibly longer.” But an “incipient species” is not the same as a new species. In The Origin of Species, Darwin wrote: “According to my view, varieties are species in the process of formation, or are, as I have called them, incipient species.” 7 But how can we possibly know whether two varieties (or races) are in the process of becoming separate species? Saint Bernards and Chihuahuas are two varieties that cannot interbreed naturally. The Ainu people of northern Japan and the !Kung of southern Africa are separated not only geographically, linguistically, and culturally, but also (for all practical purposes) reproductively. Are dog breeds and human races therefore “incipient species?”
There’s no way we can know, unless we observe varieties becoming separate species at a future date. Designating two reproductively isolated populations “incipient species” is nothing more than a prediction that speciation will eventually occur. It is a far cry from observing the origin of a new species.
Read the rest here. References to peer-reviewed literature are provided.