See how easy it is? Even early agriculturalists, and even hunter-gatherers could do it.
And how did they learn this?
By observing nature. Just as, many years later, Darwin did. But he figured out the details and wrote it down.
But you say, "That's selection, but it's not evolution." When you select for certain traits (or nature selects for certain traits), other traits are less common. These small changes add up over time.
Fast forward a hundred thousand years and we'll see what we have. That's tough to do. Fortunately, with evolutionary theory, we can look backwards a hundred thousand years, or a million years, and see what we have.
Evolution is often slow, but paleontology and genetics provide a good look at the past and can see the changes that occurred. And, what to you know, these two different approaches support each other.
You say, "Evolutionary theory didn't have squat to do with it."
Sure, evolutionary theory didn't have anything to do with the changes in the past, as Darwin proposed his theory in 1859. But his theory (as modified and improved for 150 years) accounts for those changes and explains those changes.
Early folks through observation came up with a lot of the details, but it took the genius of Darwin to bring it all together and write it all down. And what he wrote down is the beginning of evolutionary theory--and it has everything to do with it!
Which was the point. Evolution theory didn't contribute squat. It only attempts to explain in retrospect how we got here. (And I think it's a bad, extremely week, explanation.)
It didn't contribute to the breeding or selection experiments. Men didn't need evolution theory for that.
ToE didn't contribute to the discovery of genetics, you can thank the creationist George Mendel for that.
ToE didn't contribute to the discovery of vaccines, again thank creationists.
In fact, the only thing ToE contributes to is the government grant industry.