Thumbs Up!

Here’s an experiment: try going fifteen minutes without using your thumbs. Bet you can’t do it. We may not give them a second thought, but life would be very difficult without thumbs.

Last week, my left thumb was knocked out of commission after I sustained a painful bite from one of my lovebirds (they really deserve a more appropriate name… devil birds, perhaps). I introduced you to my birds, Tuukka and André, in last February’s Bird Brains. Well, a few days ago, in an attempt to prevent their close encounter with the ceiling fan, I was trimming their wings. I had Tuukka wrapped in a towel and turned on his back, but even with the protection of the towel, he managed to swivel his evil little head and take a hunk out of my thumb. To make matters worse, he tore off a small chunk of skin that for the next few days caught on everything I came in contact with. Putting on socks, toweling off from the shower, getting ice from the freezer – every simple task became a painful ordeal as I tried to manipulate my maimed thumb. It got me thinking about our dependency on thumbs and the crucial role they have played in our evolution.

First we must start with the hand in general. Although we now walk on two limbs, we evolved from four-legged stock, thus we are tetrapods at heart. And the majority of tetrapods sport limbs with five (or fewer) digits. Yes, many a tetrapod has lost a digit here or there. Bat fingers still come in fives but are draped in a leathery wing. Bird fingers come in a bizarre array of digits, depending on the species. And horses’ feet have been whittled down to a single lonely toe. But we humans have maintained the standard five and boast an especially talented member, the fully opposable thumb.

Although our hands and those of our closest relatives, the chimps, are similar in structure, our hands – especially our thumbs – have several key advantages. Our thumbs are longer, stronger, and more maneuverable than those of our primate cousins, whose thumbs lack the musculature of our mighty first digits. And because they are so short, the chimps’ puny thumbs cannot “oppose” their other fingers, and we all know how vital opposable thumbs are. That’s why you’ll never catch a chimp “in a pinch.” They simply lack the ability. Instead, they are forced to press their miniscule thumbs against the sides of their index fingers when picking up small twigs or snatching bugs from the forest floor.

Our opposable thumbs allow us to grip; a crucial skill in making and utilizing tools. Scientists claim the evolution of our “power grip” was crucial to wielding clubs and throwing stones; tasks that would have come in handy when warding off predators and taking down prey. The evolution of the “precision grip,” also made possible by a strong, flexible thumb, would have enhanced toolmaking, allowing our ancestors to construct the intricate objects that would accompany the rise of Homo sapiens.

Powering our thrifty thumbs are three muscles lacking in the chimp hand. These muscles provide strength and control and the small saddle joint on which our thumbs sit is key to its full opposability. So, unlike chimps, we can pinch, pluck, and snap to our hearts' content. In fact, scientists are now examining the role of thumbs in human evolution and, it turns out, those with stronger, more agile thumbs may have had an evolutionary edge over their weaker-thumbed cohorts. The ability to produce more effective tools in greater numbers may have edged out the competition among our hominin ancestors, which makes sense… Gals usually go for the bigger, better tools.

But what about in today’s modern society, where tool production has fallen by the wayside? Fewer folks actually produce their own tools, much less make their own clothing, build their own houses, or grow their own food. Do our thumbs still present an evolutionary advantage?

Perhaps if you’re a habitual gamer. Just ask gamer the importance of thumbs and I’m sure they’ll present a litany of benefits their nimble thumbs afford. Whether they’re blasting their way through Doom, leading expeditions across Monkey Island, or taking down foes in Mortal Kombat, the faster the thumb, the better their chances of conquering the universe. 

Unfortunately, this nerdy set of skills probably doesn’t confer much of an evolutionary advantage. If history is any indication, I doubt the gamers will be outbreeding the rest of us anytime soon. They aren’t exactly renowned for their sexual prowess…

Catch you next time!