3/28/2023 0 Comments Chimpanzee hand compared to human![]() ![]() Your human ability to nimbly hold and manipulate objects between your thumb and any one of your fingers depends on more than the ideally designed proportions of your thumb, finger, and hand bones. Almécija’s analysis of primate thumb-and-finger proportions published in Nature Communications overturns the view that we humans evolved our hands from chimp-like ancestors in favor of the notion that chimps evolved their hands from hands like ours. Such manual dexterity presumably gave our ancestors something to think about and made the manufacture of tools move past the fashioning of stone axes so they could adapt and evolve to hoist themselves into the modern world. “Chimpanzees have actually evolved more than humans.” 1Įvolutionary wisdom holds that humans developed big brains and creative powers after coming down from the trees and evolving hands capable of manipulating the world around them. “Human hands have not changed that much since they diverged from chimpanzees,” Almécija says. They believe the human hand’s precision grip is not advanced but instead represents the primitive condition much like that of the last common ancestor shared with apes. They are challenging the view that humans diverged from chimp-like ancestors with hands adapted to swing from tree limbs. Evolutionary researcher Sergio Almécija and colleagues have knocked the pins from under that bit of conventional evolutionary thinking. Thumbing through the pages of most manuals on human evolutionary history, a reader would soon latch onto the idea that our precision grip was a relatively recent addition to the human repertoire. Nature World Report: “ Chimps vs Humans-Whose Hands Are More Primitive?”.Science: “ Humans Have More Primitive Hands Than Chimpanzees”.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. 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). Humans share pollical opposability with most other catarrhines (old world monkeys and apes). 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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