A complete theory of evolution must acknowledge a balance between “external” forces of environment imposing selection for local adaptation and “inter… - Stephen Jay Gould

Our indirect methods have taught us a mountain of things about horses, but if you wished to learn even more, would you rather be Whirlaway in the stretch, than interview Eddie Arcaro afterwards?

Giraffes do use their long necks to browse leaves, at the tops of acacia trees - but such current function, no matter how vital, does not prove that the neck originally evolved for this purpose. The neck may have first lengthened in context of a different use, and then been coopted for better dining when giraffes moved into the open plains. Or the neck may have evolved to perform several functions at once. We cannot learn the reasons for historical origin simply by listing current uses.

I had learned that a dexterous, opposable thumb stood among the hallmarks of human success. We had maintained, even exaggerated, this important flexibility of our primate forebears, while most mammals had sacrificed it in specializing their digits. Carnivores run, stab, and scratch. My cat may manipulate me psychologically, but he'll never type or play the piano.