Studies have shown that domesticating grain could be done in as little as 20 years; the Aztecs built floating cities on lakes; people of the Andes turned teosin

Studies have shown that domesticating grain could be done in as little as 20 years; the Aztecs built floating cities on lakes; people of the Andes turned teosinte into corn and also created potatoes, tomatoes, beans, corn, peanuts, quinoa, potatoes, tomatoes, peppers, etc all in probably less than a thousand years. A thousand years ago, a European black bear's diet was 90% meat; that dropped to around 70% in Medieval Europe; and now stands at perhaps less than 10%. In the span of 150 years American bison populations went from 60 million to 500 individuals (note: these are keystone species. Without them the Great Plains wouldn't exist and woodland ecosystems would've overtaken the grasslands). It's estimated that the Amazon rainforest could revert to grasslands in as little as 10 years if the current rate of deforestation continues. Ecosystems and environments change. Quite rapidly sometimes > the California fires of yore would roll through on a regular basis burning the limited fuel on the ground and not getting hot enough to damage the trees Yes that's exactly the point of the cultural burns