The mini-ice ages that occured between then and now just about wiped out Greenlanders.
It's still stupid to pollute our air, water and ultimately our food with toxins, but even that has been done by mankind for millenia. Those who drank water from Roman aquaducts or wine that was artificially sweetened during the Roman Empire and well beyond were subjected to overdoses of lead poisoning. Arsenic was commonly used as a medication and oracles were subjected to toxic gases in order to make predictions.
All in all, if man comes up with a "good" idea, we really should check it out more thoroughly for it's long term affects.