Steve at the WildeBeat has the scoop. Much of the credit for the current bear canister industry hinges on the fact that a guy named Garcia had a machine shop. Oh, and the fact that a hungry bear is a clever bear.
One of the things the first bear can testers noted was that when bears first encountered the canisters they might spend an hour trying to get ’em open. Over time they’d spend less and less time with the cans, then gave up on them altogether. A consequence of this was fewer campsite encounters as bears gave up on people as reliable pantries.
Yogi would not be pleased with the evolution of picnic-basket technology.