]
We have often to move our forearm very quickly, sometimes to save our
lives. The difference of one-hundredth of a second may mean life or
death to us on the face of a cliff when we clutch at a branch or jutting
rock to save a fall. The quickness of a blow we give or fend depends on
the length of our reach. A long forearm and hand are ill adapted for
lifting heavy burdens; strength is sacrificed if they are too long.
Hence, we find that the laboring peoples of the world--Europeans and
Mongolians--have usually short forearms and hands, while the peoples who
live on such bounties as Nature may provide for them have relatively
long forearms and hands.
[Illustration: Fig. 9B.--The forearm and hand as a lever of the third
order.]
Now, man differs from anthropoid apes, which are distant cousins of his,
in having a forearm which is considerably shorter than the upper arm;
whereas in anthropoid apes the forearm is much the longer. That fact
surprises us at first, especially when we remember that anthropoids
spend most of their lives amongst trees and use their arms much more
than their legs in swinging the weight of their heavy bodies from branch
to branch and from tree to tree.
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