We have domesticated crops over a very long period of time, like tens of thousands of years. And crops get - seeds get carried. Sometimes, if they're very small seeds, they get scattered off trucks. Pollen travels.
Weeds do become resistant to herbicides, and it needs to be managed with multiple herbicides.
Even as the population doubled from three to six billion, we managed to race ahead with all kinds of technological and scientific events in agriculture - from using more fertilizers to mechanization to advanced plant breeding.
Jumping genes are fundamental because they're agents of change. Everybody knows that organisms evolve. What makes them evolve is that their genes are dynamic and in motion. A familiar example is the stripe-y corn - called Indian corn - that you buy in the fall.
The more we can grow on already cultivated land, the better.
