To understand how evolution works its magic across the evolutionary tree, we often invoke the twin concepts of homology and analogy. Homology refers to shared traits derived from a common ancestor. Thus, the human hand is homologous with the wing of a bat, since both derive from an ancestral forelimb and carry the exact same number of bones to prove it. Analogies, on the other hand, arise when distant animals independently evolve in the same direction, known as convergent evolution. The parental care of the discus fish is analogous to mammalian nursing but certainly not homologous, since fish
...more
