For one thing, their hands each had only a single opposable thumb instead of the normal two.
"A door that happened to have four fingers and an opposable thumb?"
Hands must also have opposable thumbs, as described later in the text.
It is not the opposable thumb so much as the size of our brains.
One of the human hand's five digits is an opposable thumb.
He pulled nervously at one opposable thumb, then the other.
Her eyebrows lifted at the sight of the opposable thumb.
No, but maybe I'll buy you a set of opposable thumbs.
You're pretty smart for a guy with no opposable thumbs.
Its three-fingered hands had what looked like opposable thumbs on either side.
