That's an a-historical point of view. There have been several environmental catastrophes, including some causing massive climactic shifts introduced by prehistoric humans, some of them are documented in 1491, by Charles Mann. Poor farming practices, including some that have been practiced for thousands of years, are a huge factor in desertification. I completely agree that the rate and scale of environmental catastrophe is new, but the risk of it and tendency towards it is not. While I think capitalism is ABSOLUTELY the single greatest barrier to addressing the catastrophe, the scale and speed of that catastrophe could be just as easily tied to population growth as the emergence of capitalism.