The Beak of the Finch: A Story of Evolution in Our Time

The adaptive landscape refers to a data visualization model pioneered by Dolph Schluter. It locates individual variations (for example, different sizes of finch beaks) within a topography of superiority and inferiority within a given habitat. Peaks represent variations of highest fitness between which lie valleys of unfitness. An individual might find itself on a peak, in a valley, or somewhere along a slope. Evolution tends to push populations in the direction of their adaptive peak(s), although the landscape inevitably shifts in response to environmental change.

Adaptive radiation describes the way evolution unfolds after natural selection drives similar, competing species to diverge. After the divergence pushes the rivals into exclusive niches, each competitor begins adapting expansively within that niche, forging new “forks in the road […] new branches on the tree of life” (142).

Character displacement is the phenomenon by which a species evolves its way out of competition with a rival by changing its characteristics. David Lack suspected character displacement among Darwin’s finches. Dolph Schluter confirmed it via his adaptive landscape tool, which correctly and precisely predicted the adaptive peaks the finches had evolved based on competition and seed supply; thus, “[the finches] are the best case of character displacement ever found” (154).