come OUT 短篇英语散文:How come our fingers are different sizes and lengths?

短篇英语散文:How come our fingers are different sizes and lengths?  

How e our fingers are different sizes and lengths? asks Alec Pemara
a student in Manhasset
NY.
hands and fingers aren't unique to human beings; other primates have them
too. Take a look at gorilla or chimp's hands and you'll see a set of four fingers
varying in length from index to pinky
along with a real thumb. (While other animals
such as raccoons
have paws that resemble hands
official "hands" belong only to primates.)
Hands are useful for grasping—hanging onto a tree limb (or hanging onto a ladder)
picking berries (or picking up groceries)
throwing a clod of dirt (or throwing a baseball). If our fingers were the same length
our hands wouldn't be such flexible tools. When we hold a spherical object like an orange in the palm of our hand
the fingers actually curve around evenly
giving us a firm grip. Tapering fingers (and strong thumbs) allowed early humans to use specially-shaped stones to smash
scrape and cut other objects. (A long pinky finger would be more likely to get caught and squashed itself.) Besides precision grips
our different-length fingers also provide a balanced support for crawling or leaning on our hands.
Among different species of primates—from baboons to monkeys--fingers and thumbs vary in shape and length. Long
thin fingers are best for tree-swinging. Chimpanzees
who themselves make and use simple tools like termite-catchers
have hands that most resemble ours.
Most primates
from gorillas
orangutans
and chimpanzees to Old World monkeys
have "opposable" thumbs that can bend ouard at up to a 90-degree angle from the other fingers. The most developed opposable thumbs are especially handy for holding small objects beeen thumb and index finger.
Thumbs have only one middle joint
rather than the o joints found on the four regular fingers. The four longer fingers can curl further around an object
while powerful muscles allow the thumb to "lock in" the grip
vise-like. Human opposable thumbs are
pared to those of other primates
bigger and stronger. A chimp can pick up a peanut from the ground
but can't open a tightened lid on a jar of peanut butter. Our own powerful thumbs seem to have evolved in tandem with our tool-making skills.
Among individuals in each primate species
finger and thumbs vary
too. Compare your hands to those of your friends
and you'll see subtle and not-so-subtle differences. Boys and men often have longer ring than index fingers. Girls and women tend to have similar-length ring and index fingers
or shorter ring fingers. Scientists say the differences are due to the influence of the hormones estrogen and testosterone in the womb.
One study found that male physicists
chemists
and mathematicians had ring and index fingers about equal in length
while male economists and social scientists had longer ring fingers. Another study found that men with substantially shorter index than ring fingers tended to be more physically aggressive than others.