>They could have developed bronze working independently. Newton and Liebniz both figured out calculus at the same time. But even stories passed around can be enough to spark discovery. Tell someone that magicians on the other side of the world have mixed sulphur, charcoal and saltpetre and they'll figure it out quickly, even if it takes a while to get the formula right. If bronzeworking stories were being traded as far as china I'd be surprised if bronze objects and techniques weren't also. The reason leibnitz and newton both developed calculus is because they were part of the same closely connected community of academics all working on the same thing and sharing the same discoveries. Calculus was just the next step. There wasn't quite that level of interconnectedness between China and Europe. >Mostly right I think. Bronze working is a necessary step to iron working, and iron agricultural tools are what led to China's large population. But it's important to not underestimate stone age potential. Tenochtitlan had one of the largest populations in the world, made possible by artificial island gardens, all built with stone tools. Also, China's threat was usually technologically inferior barbarians who were militarily superior, a problem that plagued most early civilizations. They managed with walled cities and massed levees of pikemen and crossbowmen. When horses showed up, they created a massive state breeding program to get their own cavalry quickly, a process that could have worked against opponents arriving with metal weapons. I agree that the progress of neolithic civilisations is often underestimated, but there's still the core problem that even if they manage to grow a large population and centralise them, most of them will be working to sustain said population and they'll be highly vulnerable to any disruption in their food supply. Basically a malthusian trap. The same isn't as true of a society with metal tools. Said tools vastly increase efficiency so that more labourers are freed up for megaprojects like emergency horse breeding and pike formations. Also, I'm not sure bronze working is a necessary step to iron. Iron was always hanging around in the background of bronze societies (at the very least in the form of meteoric iron) but it's much harder to produce/work and requires a lot of specialist knowledge to produce iron tools that are better than bronze ones. Once the tin trade routes were cut off in the bronze age collapse it was adopted out of necessity, but if those trade routes had never existed to begin with (as in Africa) I think we'd have gone straight from stone to iron. Although you may be right as the amerindians never made that leap, even though they had meteoric iron. Hard to know.