3 Interestingly, the thumb bone from Orrorin tugenesis-an incomplete collection of human-like bones and teeth that evolutionists date at 5.7 to 6.1 million years-does have these typically human curves. Australopithecines also lack these grip-enhancing contours. They can only manipulate small objects by gripping them between the thumb and index finger tip-to-tip or pad-to-side, a pad-to-pad grip being impossible for them. Living great apes like chimpanzees and gorillas do not have these bony contours. Image by Sergio Almécija, Salvador Moyà-Solà, and David Alba, via PLoS ONE. And beyond that is another more shallow depression (in blue) for the soft tissue of the thumb’s tip ( distal ungula pulp), which being smaller and less mobile is able to securely grasp a tiny object. Just beyond this tendon’s insertion, an especially large depression (in green) accommodates the bulky soft tissue of the thumb pad ( proximal ungual pulp), which is soft and mobile enough to adapt to the shape of an object being grasped. As shown above, the tendon (shown in red) that enables you to freely flex the end of your thumb is accommodated by a particularly large depression (in orange, proximopalmar fossa). Each curve in the contour of the bone at the end of the thumb ( pollical distal phalanx) enhances the human ability to feel and grip tiny objects gingerly but securely. 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.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |