The finches that Charles Darwin collected in the Galapagos Islands are considered textbook examples of how a single species differentiated into many to exploit different resources. Subtle changes in the size and structure of beaks among the six species of ground finches have been called “evolution caught in the act.” But are they really one species, or several? In Science Smackdown, we let experts argue both sides of the question.
The textbooks are wrong, says ornithologist Robert Zink of the University of Minnesota’s Bell Museum of Natural History. The ground finches may seem to be different species, at least with superficial comparison, but they’re stuck in what he calls Sisyphean evolution. “Species kind of get started, but . . . they never make it to the top of the hill,” Zink says.
In a recent paper in Biological Reviews, Zink helps make the case. “None of these ‘species’ are distinct,” ...
