The pinky is extremely useful - any alien race without it would be plagued by nasal mucus and earwax.

(There's a very good sci-fi short story, the author of which I can't remember, in which interstellar space travel is very simple and easy but humans have somehow overlooked how to do it. So, when an alien race is looking around for a planet to invade, they decide that the inhabitants of Earth must be very primitive - but when they get here, sometime in the late 20th Century, their weapons are equivalent to 15th Century Earth weapons and they're defeated almost immediately.)