He never evolved.

I think a lot of us could do the same thing if given the opportunity, after what we've been through the last 3 years.

Who can throw the highest or farthest or make the deepest dent? Chimp equivalent of a pissing contest?

Chimps are heirarchical. Jane Goodall reported on some of the techniques that male chimps use to demonstrate dominance, e.g. loud hooting and aggressive posturing to intimidate others. Could this rock-throwing ritual have something to do with that? Contestants throwing a rock at a tree like the phrase "tossing your hat in the ring" to show who is in on the challenge to be top chimp.

Some things to observe for more insight might be the age of the rock throwers, what they do before this action and after they walk away, whether there are chimp witnesses, what uses the trees they hit might or might not hsve for chimps. Chimps make beds in trees at night. They also use twigs and lesves to scoop out termite snacks, and sometimes use small sharpened branches as spears. Do the trees they target with rocks have any relation to the ones they use as beds or tools?

Anything wrong with the trees they target, e.g. a tree disease?

Will look forward to answers the observers come up with as they figure it out.