marijuana only grows where it's been spread by another plant, 2 other plants to be exact, a male and a female...and there's only certain patches of land in certain places where it's growing like that, there has to be a high population of it and of different strains for it to keep growing regularly....just like you can't have one mom and dad human that can keep the human race going, it takes many different males and females of many different origins, if one male and female kept trying to breed new generations with just their own kids, then it would be like incest, and the mutations would eventually get so bad that they wouldn't survive as a breed....in other words, you'd see other weed plants around, older than those, for many square yards, if it were an indigenous strain...if there's one or two or three by themselves then someone planted them, and that will be the breeding grounds for many generations of mutated, incested plants in the future