Opposable Thumbs

Not set off by anything in particular: I am tired of people saying that humans are the dominant species because of our opposable thumbs. To be honest, I'm not sure if anyone says this seriously. Maybe they're all being facetious, and the joke's on me. But assuming they do mean it, they're not thinking very hard.

It's not hard to see why primates have opposable thumbs. You can get much more purchase on a branch by gripping it with your fingers above and your thumb below, than you can with just your fingers. Rats can grip things, but they can't swing from tree to tree. Humans have opposable thumbs mainly because their recent ancestors did, and there's no evolutionary pressure against them.

It's certianly not like humans have much use for opposable thumbs. Perhaps when they climb trees, thumbs are as useful as ever. But opposable thumb-partisans claim that humans are uniquely suited to use tools. Is there any reason to think that? As I say, thumbs are important for hanging on to branches. But what simple tools work better with support from behind? I can use pens, forks, knives, hammers, screwdrivers, ladders and brooms all perfectly well without thumbs. I seldom even pick things up with my thumbs. I pick them up between my index and middle fingers, and I *like it*.

Opposable thumbs are useless. If you want to claim that unusual appendages are the key to human success, how about having extra arms, like a rhinoceros beetle? Or having opposable big toes, like a chimp? Or having more than one opposable finger per hand? Octopusses can pick up all kinds of things, with completely opposable hands, but they're still not doing as well as less pathetic animals. Let spider monkeys have their 5 prehensile limbs. The actual secret to humans' evolutionary success is that we? Are awesome.