It makes you sound delusional to say that corn is fully a product of ancient genetic engineering but it is consensus science/history/botony as far as I understand

Maize domestication is one of the greatest feats of artificial selection and evolution, wherein a weedy plant in Central Mexico was converted through human-mediated selection into the most productive crop in the world. In fact, the changes were so astounding that it took much of the last century to identify modern maize’s true ancestor. Through modern genetic studies, the molecular basis of this evolution is being unraveled. Maize’s new morphology and adaptation to diverse environments required selection at thousands of loci, and we are beginning to understand the magnitude and rates of these genetic changes. (Tracking Footprints of Maize Domestication and Evidence for a Massive Selective Sweep on Chromosome 10 - In the Light of Evolution - NCBI Bookshelf)

Re the Amazon, in 1491, Mann talks about how it was densely populated and farmed specifically with a lot of trees which Europeans didn't recognize as domesticated. Like in other places they just thought it was "like a garden of eden" where god had simply placed everything nice and convenient for the inhabitant instead of an intensely designed intentional farming system created by humans.