Hello. Look into the history of cannabis. It's been grown around the world for thousands of years.
Just in the Kush valley there would have been variations in the taste and high even back then.
Then the farmers would cross different plants with their neibour, and only grow the seeds from the best plants next year.
Then world trade happened and you get all the hemp that was grown for rope and sacks getting stronger.
Then they started crossing the indica strains with the sativa (hemp) strains to get where we are today.
There's the old story of how the plantation workers noticed the birds acting funny after look for seeds in the mature hemp in Jamaica. Then trying some. Ire Man...
Barney Seeds tells his story of how he gathered his starter strains in the Afghani region and then inbreed them to get stronger strains... to where they are today.
Read about the history of cannabis... It's facinating...
Chuck.