Long before humans became recognized as the animal kingdom’s predominant tool makers, our primate ancestors developed the five-fingered hands that would one day allow us to manipulate everything from prehistoric hammerstones to a spacecraft’s flight controls. With a complex structure that includes 27 bones, 29 joints and more than 100 distinct ligaments, our hands give us the ability to interact with our environment in some truly astounding ways. Powerful enough to grip weapons like swords and axes, and yet sensitive enough to delicately pluck the strings of a guitar, the human hand emerged more than a million years ago as our first and most fundamental tool.
The thumb, which is able to reach across the palm to touch the other four digits, accounts for roughly 40 percent of the human hand’s capabilities. In fact, it is so integral to our hands’ function that surgeons will sometimes amputate a person’s big toe to replace a lost thumb.
It’s also worth noting that while our hands are quite strong, their strength is derived from muscles in the forearm, which are connected to the finger bones by a series of long, flexible tendons. The hands themselves, however, have very little musculature. Wiggle your fingers, and you can even watch these muscles spring into action just below your elbow.
This arrangement, wherein our fingers are remotely controlled by the more robust muscles in ours forearms, gives our hands an added degree of power and precision. In an article published by the BBC, Dr. George McGavin describes the hand as “a bony puppet, lashed together by ligaments and controlled by the forearm.”