Which invention was a big mistake for humanity?

the process by which we extract cocaine from the coca plant is certainly a discovery that we could have went without, this substance has caused so much suffering everywhere it goes. every form of explosives used to kill people is another one, from guns to nukes. we should have stuck to swords. at least with a sword you have to work hard for your kill and your adversary has a chance to fight back. a third one is all technology based on petrolium, I know it brought so much cool stuff but the price our ecology is paying can't be worth it. we should have stayed more simple until we come up with technology that is actually sustainable.