[Qwertious]

>Yes, clearly. All the measures defined in this article are arbitrary (e.g. vehicular land speed), and so let's propose an arbitrary one for intelligence: Ability to prove mathematical theorems. Humans have proven many. Apes have proven zero. That is an extreme discontinuity. We can propose many others, of course: complex language development, building skyscrapers, landing on the moon, etc..

That's at least partially explained culturally - pressure to go attent university leads to more exposure to mathematics and stuff.

Also, how do you actually know that gorillas haven't proven mathematical formulas? I mean, they don't have writing so perhaps there were gorilla mathematicians before, they just weren't recorded.