Chimps and nuts

Even after a year of exposure to the nuts and rocks chimps didn't figure out that they could crack the nuts. (Some chimps elsewhere do crack nuts with rocks.) "According to the zone of latent solutions hypothesis in Anthropology, chimpanzees ... can reinvent cultural behaviors individually." The experiment seems to disprove this; chimps have to learn how. They apparently show each other. I'd never heard of the zone of latent solutions before, and it sounds overly expansive. Cats are natural hunters, but to be effective hunters they have to learn--and that's just using native equipment, not external tools.

I wonder how much the chimps learned from watching humans.