You're confusing the object for the verb. The sex habit is "jerking off" not "to internet porn", and all it takes is a simple youtube search for "bonobos jerking off" to see that you're wrong.
I would argue jerking off to Internet porn and jerking off to a fantasy are both exhibiting the same behavior, just like a polar explorer from the 19th century and a lunar explorer from the 20th century are exhibiting the same behavior.
I'm not saying humans 200 years ago were incapable of such things.
What I'm saying is that bonobos don't read or write Kama Sutra.
In any case bonobos would not write Kama Sutra even in 20,000 years. Your timescale and argument is way off.
Downvoters: I've no more apples for you.