Fixity of species and common descent

Studying the biogeographical links between different parts of the world can deepen our understanding of the evolutionary relationships between different populations within a species, between different species, and among higher taxonomic groups. Because different groups diversify at different rates, the evolutionary history of a single species revealed by biogeography might help clarify the relationship between entire families of some different group. These testable predictions about biogeography are powerful tools for scientists.

By the account in Explore Evolution, this predictive power is nonexistent, and biogeography only allows us to reject the notion of species fixity, nothing more. Instead of examining the many ways that biogeographic studies can inform our understanding of evolution, Explore Evolution simply dismisses the field as irrelevant. In particular, the authors claim that biogeographic evidence cannot distinguish between common ancestry and creationist "orchard" models. Such "orchards" have no scientific basis. Despite the book's claim to be "inquiry-based," Explore Evolution never clarifies how readers might themselves investigate such an orchard.

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