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mind & bodyanalysisThe Conversation
Why are our fingers different lengths?
Finger lengths differ because each finger has a job, and evolution and development shaped those roles. The middle finger is usually longest and acts as the hand's central axis, working with the ring finger to hold grip steady. The index finger is shorter and more independent, which suits pointing and precise movements. The pinky steadies the outer edge of the hand when holding large objects. The thumb is about three-quarters the length of the index finger, but its rotating joint lets it oppose the other fingers for pinching. Genes guide how fast each finger bone grows before birth, and hormones such as testosterone and estrogen influence proportions, which is why families often share hand features.
Genes set the growth rate of each finger bone before birth, so small differences in timing produce different lengths. Joints and tendons are shaped to match each finger's task, from the thumb's rotating joint to the index finger's independent movement.
Finger proportions are a useful example of how the body's structure is tuned for function. Humans share the long middle finger with other apes, a hint of the hand's evolutionary history.
Humans share a long middle finger with chimpanzees and gorillas.
background
A hand is a prehensile, multi-fingered appendage located at the distal end (extremity) of the forelimbs/upper limbs of tetrapod animals — chiefly primates such as humans, chimpanzees, monkeys and lemurs — that is used primarily for grasping and object manipulation. Some non-primate arboreal vertebrates with opposable fingers such as the koala (who has two opposable thumbs on each "hand" and friction ridges extremely similar to human fingerprints), opossums, chameleons and leaf frogs are often also described as having "hands" instead of paws or feet. The giant panda (who has a "pseudothumb" made of a sesamoid wrist bone to aid grasping) and the raccoon are sometimes also described as having "hands" due to how they have adapted or improvized the upper limbs for grasping, although they actually lack opposable fingers.
From Wikipedia: Hand (CC BY-SA 4.0) ↗ · text CC BY-SA 4.0watch · 1:55
1:55Why do we generally have five fingers on each hand? ✋#science #short #alanturing #sciencefacts
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