In biology class we learn about Mendel as one of the pioneers of biology for he determined that tall plants breed tall plants and short ones breed short ones. However, it’s clear that even in the ancient of days there was some knowledge of how genetics worked. Take, for example, the following passage from Genesis where Jacob’s uncle Laban has asked what Jacob would like as repayment for all the work he’s done.
“Don’t give me anything,” Jacob replied. “But if you will do this one thing for me, I will go on tending your flocks and watching over them: Let me go through all your flocks today and remove from them every speckled or spotted sheep, ever dark-colored lamb and every spotted or speckled goat. They will be my wages. And my honesty will testify for me in the future, whenever you check on the wages you have paid me. Any goat in my possession that is not speckled or spotted, or any lamb that is not dark-colored will be considered stolen.” Genesis 30:31-33(NIV)
So they clearly understood in Biblical times that spotted sheep would only breed to produce spotted sheep – no white sheep would come from that union. That is why they will know if he has stolen any livestock if they are pure white. What they didn’t know, however, was the concept of dominant traits.
Laban, who we already know is quite a tricky guy, decides to be slick by removing all of the male spotted animals. So, he figures, how will Jacob increase the numbers of spotted animals? What neither of them knows if the concept of dominant traits, so Jacob puts striped bark in front of the sheep when they mate and then they have striped and spotted offspring. So to him, it was the striped bark that did it. We know, of course, that the striped-traits are dominant traits.
So they understood SOME genetics back then, but they didn’t quite have the whole picture.