Hands of People Vs Other Primates
There was some discussion of people hands and how they differed from our primate cousins' hands. (Was it suegypt?) I found this article in Science (Paleolithic Technology and Human Evolution, Science, 1748 (2001); Stanley H. Ambrose, et al.
"Oldowan" refers to the style of tools found 5 to 2.5 million years ago, in this excerpt. Apparently, our hands and wrists have evolved away from use for locomotion and toward use of our thumbs and powerful forearms for manual tasks. Chimps favor using the force of the upper arm and shoulder when using tools. The human structures allows improved precision when strength is also needed for work with the hands. Say, flaking out a stone axe. I enjoy how someone took the time to teach a bonobo tool flaking.
Modern homo sapien forearm development
"Oldowan technology seems simple, reflecting the mental capacities of extant apes (24), but it actually reflects manual skills far exceeding those of chimpanzees. For example, Kanzi, a bonobo (pygmy chimpanzee, Pan paniscus), was apprenticed for 3 years in stone tool flaking by direct percussion of hand-held cores (25, 26) but was unable to strike forcefully and accurately at the correct angle or position on the platform. His small flakes and battered cores did not resemble Oldowan artifacts.
Kanzi used sharp-edged flakes to cut a rope to open a food reward box. He cut slowly, with little downward pressure, moving his whole arm, mainly from the shoulder, with an immobile wrist. Wild chimpanzees also move their arms mainly from the shoulder and elbow when cracking nuts (7). This contrasts dramatically with the human dexterity in precision tool use that is afforded by a mobile wrist. Anatomical limitations on joint motion and power and on precision grips, due to design primarily for quadrupedal and arboreal locomotion (27-29), may account for the poor performance of chimpanzees in stone tool-making and use. Long curved fingers and a short thumb hinder opposition of their fingertips in a strong pinch grip.
Humans have short straight fingers, a long stout thumb, and fingertips with broad fleshy pads underlain by wide apical tufts of bone, which increase stability when gripping small tools. Chimpanzees have narrow fingertips and lack the forearm muscle for powerful thumb flexion. Palm muscles that strengthen the opposable thumb grip are either absent or relatively weakly developed. Australopithecus afarensis (3.8 to 2.9 Ma) had chimpanzee-like narrow fingertips (27), but those of A. africanus (3.0 to 2.6 Ma) may have been more human-like (30).
The chimpanzee wrist locks to prevent overextension during knuckle walking, which limits rotation of the wrist (29). This may inhibit wrist motions such as those humans use to throw a fastball, flake stone, and manipulate small tools precisely. Additional biomechanical, myographic, anatomical, and neurological ( positron emission tomography scan) studies (27, 28, 31) of the kinematics of chimpanzee and human tool use are needed to evaluate this impression of limited chimpanzee arm and wrist flexibility during tool use."
"Oldowan" refers to the style of tools found 5 to 2.5 million years ago, in this excerpt. Apparently, our hands and wrists have evolved away from use for locomotion and toward use of our thumbs and powerful forearms for manual tasks. Chimps favor using the force of the upper arm and shoulder when using tools. The human structures allows improved precision when strength is also needed for work with the hands. Say, flaking out a stone axe. I enjoy how someone took the time to teach a bonobo tool flaking.
Modern homo sapien forearm development
"Oldowan technology seems simple, reflecting the mental capacities of extant apes (24), but it actually reflects manual skills far exceeding those of chimpanzees. For example, Kanzi, a bonobo (pygmy chimpanzee, Pan paniscus), was apprenticed for 3 years in stone tool flaking by direct percussion of hand-held cores (25, 26) but was unable to strike forcefully and accurately at the correct angle or position on the platform. His small flakes and battered cores did not resemble Oldowan artifacts.
Kanzi used sharp-edged flakes to cut a rope to open a food reward box. He cut slowly, with little downward pressure, moving his whole arm, mainly from the shoulder, with an immobile wrist. Wild chimpanzees also move their arms mainly from the shoulder and elbow when cracking nuts (7). This contrasts dramatically with the human dexterity in precision tool use that is afforded by a mobile wrist. Anatomical limitations on joint motion and power and on precision grips, due to design primarily for quadrupedal and arboreal locomotion (27-29), may account for the poor performance of chimpanzees in stone tool-making and use. Long curved fingers and a short thumb hinder opposition of their fingertips in a strong pinch grip.
Humans have short straight fingers, a long stout thumb, and fingertips with broad fleshy pads underlain by wide apical tufts of bone, which increase stability when gripping small tools. Chimpanzees have narrow fingertips and lack the forearm muscle for powerful thumb flexion. Palm muscles that strengthen the opposable thumb grip are either absent or relatively weakly developed. Australopithecus afarensis (3.8 to 2.9 Ma) had chimpanzee-like narrow fingertips (27), but those of A. africanus (3.0 to 2.6 Ma) may have been more human-like (30).
The chimpanzee wrist locks to prevent overextension during knuckle walking, which limits rotation of the wrist (29). This may inhibit wrist motions such as those humans use to throw a fastball, flake stone, and manipulate small tools precisely. Additional biomechanical, myographic, anatomical, and neurological ( positron emission tomography scan) studies (27, 28, 31) of the kinematics of chimpanzee and human tool use are needed to evaluate this impression of limited chimpanzee arm and wrist flexibility during tool use."