Why Opposable Thumbs Exist

Why do opposable thumbs exist in humans and other primates?  Scientists generally agree that the appearance of the opposable thumb was a key evolutionary point in the development of our species.  It is what allowed primates to grip and climb and move into the trees, away from the realm of large predators looking for a meal.  Opposable thumbs also proved to be pretty handy from a toolmaking and tool using perspective, whether the tool was a stick to be manipulated or a rudimentary axe.

All of this is true,  Curiously, however, scientists haven’t fully explored whether the opposable thumb was developed in anticipation that modern humans who are too cheap to buy a nozzle for their garden hose might need the thumb to water their yard and plants on a beastly hot summer day.  Sure, the opposable thumb might not have been evolved specifically for watering and hose wielding, but it sure works well for that purpose — whether you want to generate a gentle sprinkle or a high velocity jet to reach the side of the yard beyond the length of the hose.

How do we know for sure that our distant ancestors weren’t big on watering?

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Thumbing It

The other day I inadvertently caught my thumb in a door I was closing.  My thumb throbbed, I cursed, and then I realized with a start that until my poor pollex was 100 percent again I was totally unable to fully participate in essential activities of modern life.

The development of an opposable thumb has long been viewed as a crucial step in the human evolutionary process.  The thumb is a simple body part, made up of bones and hinges.  Yet the fully opposable thumb is unique to humans, and its development allowed humans to become complex organisms.  The thumb permits us to grip items securely and throw them accurately.  The thumb is essential to the use of the fine motor skills that allow us to perform detail work.  It is what made humans into toolmakers and tool users.

In the modern world our thumbs are more important than ever before.  They are our principal texting digits.  Your thumb performs the swipe that unlocks your iPhone.  Your thumbs anchor your hands on a computer keyboard and pound the space bar when you type your report.  Your thumb is what empowers you to open a clutch purse, use a bottle opener, pry open a child-proof container, and take notes with a pen.  Of course, it also allows you to signal an interest in hitchhiking and indicate ready assent in a noisy place.  The list of activities that require a thumb is endless, and it will continue to grow as inventiveness moves our species toward even greater reliance upon handheld devices.

With the enormously increased use of our thumbs these days, you’d think that doctors, physical therapists, and surgeons would be besieged by people with thumb-related ailments — but that doesn’t appear to be the case.  The humble thumb abides.