Seriously, if you think about it the thumb allows us to grasp things. The muscles never evolved for fine motor dexterity.
I never thought about thumbs in this way. Makes me think about all that gaming I used to do when I played on my Nintendo and Super Nintendo. And what about text messaging? I don’t do that heavily, but I’m sure there’s some people that use their cell phones in conjunction with AOL Instant Messenger. Don’t mess up your hands.