The key word there is over time. Like decades. Just think, the Spanish brought marijuana to the new world, and it took hundreds of years to geet what they have now, or had. Most of th very best Land Races have been destroyed. Starting with Nixon, and his paraquat, and then the war in Colombia, and then the switch from weed, to coke plants.
Nixon had a really devastating affect on the old Mexican landraces in the early-mid 70s. Some of those old landraces were the best of the best. Oaxacan, Michoacan. I remember getting hose in the early 70s, and they would literally blow your head clean off. Seeds and all. But by 1974, the majority of these strains were gone, or all but gone.
In 1974, there was a really big eed drough all summer. No good weed to be found. Then after the summer, Colombian started trickling in. Before 74, you rarely sw alot of colombian. Not saying you never saw it, but Mexicans were par for the course. Unless you knew someone importing Colombian. I was lucky eough to have an older friend, whos older brother worked for a shipping company out of Key West, and he used to bing in about 50lbs of Colombian a month. He did this from about 1970-77. And lot of the time, when he would bring in the 50lbs, they sold it by the lb, and no oz, and much of it went out of town to bigger cities, so sometimes it wasnt available here in the home town. But starting in late 74, Mexican was always labeled as shit weed, and colombian became the norm. Reds, and Gold. With Red being more common. Then in 75, paraquated Mexican started showing up. I remember one time there was some going around called Diesel Weed. It smelled just like diesel fuel. I wouldnt smoke it. One time a carload of us were driving around, and someone lit up a jint of it, and after a few hits, the shit caught on fire on the end. A in there was a fucking flame on the end of the joint. And Like I said, I wouldnt smoke it.Then there was another type, they called cat food. And it did the same shit. It would combust aftr a few hits, and people would still smoke it. A buddy of mines little brother smoked some of it, and had a stroke. He was 14 years old. He told a dr what he had smoked, and dr said it was most likely Paraquat. He lived, and is still alive.
But back to the subject. It takes an extremely long time for plants to stabilize on their own to a new environment, and it takes literally thousands of plants each generation, if you expect it to adapt, and keep the best traits.
But by seective breeding, and selection, you can make this happen much faster, BUT, if you breed for certain characteristics, such as mold resistance, and faster finishing times, you may also sacrifice Potency in the process. Nothing says the very best plants are going to have the traits you want, and are breeding for. So theres a trade off.