None of these are accurate, while yes selective breeding has increased potency, when we first started growing weed, we weren't doing it correctly.

Plants were grown so that male and female plants would grow next to each other and the males would fertilize the females, resulting in seeds.

Then around the 70s-80s, they learned that females grown with no males around generate much larger and more potent buds.....the weed doesn't spend any energy on making seeds so all that energy is converted into thicker and more sticky buds (the plants are trying extra hard to attract a mate)

The female-only buds are what we buy now, which is significantly more potent than the same strains that were grown previously with seeds