![]() So never take your thumbs for granted-especiallynotwhenyou’retyping. Take away the thumb, she says, and Facebook would need a different icon for “Like,” you couldn’t thumb your nose at anyone, and umpires would have to find a less satisfactory gesture for throwing players off the field. “I may throw like a girl,” says Suzanne Kemmer of Rice University, “but I throw better than any chimpanzee.” Kemmer, a linguist, thinks that by enabling fine motor skills the thumb promoted the development of the brain. His recent paper in the Journal of Human Evolution suggests that an overlooked factor in thumb evolution is the nondominant hand-the one that holds the rock while the dominant hand shapes it into a stone tool.Ī rock for throwing is a kind of tool, of course, and the cupping grip a way of using it. ![]() Even surgeons don’t.” Marzke has researched other grips, especially the “cupping,” or “wraparound,” grip, work followed by Alastair Key of the University of Kent, who used sensors to measure the forces on the digits of knappers as they chipped at rocks to replicate primitive tools. “But if you think about it, you don’t really use it that much. We observed grips by the hand during locomotor and manipulative behavior of captive chimpanzees to improve our ability to interpret differences between chimpanzees and humans in hand morphology that are not easily explained by current behavioral data. The two-finger precision grip was important in evolution, says physical anthropologist Mary Marzke of Arizona State University. “It’s not settled,” he said in an interview, “but the evidence suggests that the male hand evolved to be a better club, while the female hand maximizes dexterity.”Ĭarrier’s controversial hypothesis is part of a reassessment of the human thumb by anthropologists, who for a long time focused on its role in activities like picking up a grape. (Crucially, male index fingers are short relative to the ring fingers, so they fit snugly behind the bulge of muscle at the thumb’s base in women, the second and fourth fingers are typically the same length.) In a recent paper in the journal Biological Reviews, Carrier speculated that the bones of the masculine face may have co-evolved with the thumb to be able to withstand a punch. Other animals bite, claw, butt or stomp one another, but only the species that includes Muhammad Ali folds its hands into a fist to perform the quintessential act of intra-species male-on-male aggression.ĭavid Carrier, an evolutionary biologist at the University of Utah, believes our key advantage is the dexterity and configuration of our thumb, which folds over the second and third fingers as a buttress, concentrating the striking power and protecting the delicate hand bones. The greater mobility of the human thumb, and our enhanced ability to manipulate small objects with thumb tip-to-finger tip precision grips, likely evolved for finer manipulative abilities in the context of increased dependence on, and elaboration of, technology.Of all the motions the hand can perform, perhaps none is so distinctively human as a punch in the nose. ![]() These differences, especially with respect to relative thumb length, make it difficult for non-human primates to employ tip-to-tip precision grips when manipulating small objects (such that small objects must generally be pressed by the thumb against the lateral side of the index finger). However, humans differ from other primates in having a relatively longer and more distally placed thumb (see Relative Thumb Length) and in having larger thumb muscles (the thumb muscles constitute about 39% of the mass of the intrinsic hand muscles in humans, as compared to only 24% in chimpanzees). Close up of thumb and hand of chimpanzee in Kibale National Park, Uganda. Humans share pollical opposability with most other catarrhines (old world monkeys and apes). A fully opposable thumb gives the human hand its unique power grip (left) and. This ability is facilitated by a sellar (saddle-shaped) joint between the trapezium (the wrist bone that supports the thumb) and the first metacarpal, which allows an approximately 45° range of rotation of the thumb about its own long axis. ![]() Humans have an opposable thumb, meaning that they are able to simultaneously flex, abduct and medially rotate the thumb (pollex) so as to bring its tip into opposition with the tips of any of the other digits.
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