In the “The Common Hand” (National Geographic, May, 2012), Carl Zimmer wrote that our hands began to evolve from fins at least 380 million years ago, and within 40 million years, held five fingers. Many animals have hands. Did hands emerge independ- ently over, and over again, or did they evolve from a common ancestor? As Zimmer noted, “Darwin could re- cognize only the outward signs that hands had evolved from a common ancestor. Today scientists are un- covering the inward signs as well.”
The hand of the elephant is obscured by adaptations to withstand extreme weight. The hand of the aye-aye, a long fingered lemur, is capable of teasing out insect larvae hidden in recesses of trees. The thin-fingered hand of the bat (modeled here, on a flying fox) is adapted to stretch the membranous wing into flight- worthiness.