Does it predate written history? Are there noticable differences between cultures?
These new TV/movie adaptations (obviously impacted by Hollywood and modern beauty standards) as well as older written accounts (obviously impacted by possibly being retold hundreds of times before written down) often describe powerful generals and skilled warriors having the "most beautiful" female companions in the land. In the age of physical hand-to-hand combat wouldn't it have been more beneficial for them to marry a so called "butcher's daughter" type; a strong, tall, physically almost male-like woman?
If I'm not mistaken people have been breeding horses and cows and other work animals for thousands of years but would the scientists or intellectuals of the time realize the same also applied to humans? Wasn't the general consensus in many ways that humans were different from animals and "above" them?
How about the laymen? In the (obviously fictional) show Game of Thrones there is this big storyline around a dark-haired king having a blonde-haired son. Would something like this have caused controversy among the common folk in the medieval times? How about ancient cultures around 500BC-500AD or even older ones around the world?
You're right. Agriculture and domestication implies some understanding of genetics.
Heritability, and the mechanisms by which it happens, have been thought about since at least Babylonian times. And evolution was written about explicitly by the Ancient Greeks. What they were unsure of was the material that carried the genetic information. In the early 20th century, it became clear that this material was (mostly) DNA. In the late 20th century people figured out, based on the structure and other clues, how this is (mostly) accomplished.