I heard a podcast about this I forget which one but they said basically that corn was slowly developing and spreading north but it was not developed to support

I heard a podcast about this I forget which one but they said basically that corn was slowly developing and spreading north but it was not developed to support large civilizations like it did in the central and South America. Had Europeans not come for another 100-200 years I think it would have adapted to northern latitudes and the base for large populations and large cities would have been there. Yes the natives had corn in the north but it was a strain with very few kernels compared to what was being grown in central Mexico. I can’t recall the details but that’s the gist . I think they said only one million natives existed in the continental US when colonists first landed too