Form, function and evolution of the human hand

The modern human hand is an intriguing mix of primitive morphology and derived function. Traditionally, its form and function are explained as a functional "trade-off" between the requirements of locomotion and manipulation, but recently acquired comparative, experimental and fossil evidence suggests that this functional trade-off is more complex than conventional wisdom suggests. Moreover, when studying hand evolution within the hominin clade, the only morphological evidence comes from the hard-tissues, and evidence about hand function must be inferred indirectly from the archaeological record. We lack information about critical aspects of hand form (e.g., soft tissues) and function (e.g., neurology) as well as non-lithic evidence about behavior. Thus, comparative anatomical, experimental and ethological studies of modern humans and other primates are critical to making more informed inferences about hand use in the past. We review the relevant fossil and archaeological evidence within the relevant comparative context (e.g., other extant apes and dexterous monkeys) in an attempt to reconstruct hand evolution within the hominin clade. We conclude by summarizing our current understanding-or lack thereof-of the evolutionary history of the modern human hand.