Jacob worked for twenty one years for Lavan. During that time, he had eleven sons from two wives and two concubines. Having worked for Lavan all this time as a shepherd in charge of Lavan’s flocks, Jacob approached him with a proposition that would not cost Lavan, but could enrich Jacob. He asked for nothing. All he requested was that every unusual, spotted, speckled or striped animal amongst his sheep and goats should be taken from the herds and handed into Jacob’s care. And any new born spotted or speckled animals that came from these sheep or goats would then be his. Such animals being quite rare, Lavan thought it a great deal and agreed.
Jacob then took his spotty animals well away from the rest of Lavan’s flocks. He then made a screen of fresh saplings with the bark cut to resemble white spots on brown ( imagine a Vasarely op art painting). Whenever his animals came to the troughs to drink during the mating seasons, they would look up and see the spots. This led to the females conceiving spotty offspring. Each year Jacob amassed more and more spotties until he became very wealthy in his own right.
Now until recently and still in many superstitious societies (even in Judaism) people believed that whatever you saw when you conceived, would affect the appearance of your child. If you wanted him or her to be very religious you would look at a picture of a rabbi, or a saint or a beautiful person. If you saw something ugly your child would be ugly. There is absolutely no empirical evidence for this at all. But simple minded people might think that this was the process Jacob used to get his spotted sheep.
Now as I am not a superstitious person I just do not buy this. And what we know of animal husbandry even four thousand years ago in Mesopotamia, they didn’t either. They were remarkably skilled in breeding techniques and cultivation of healthy herds. So I believe Avraham would have used methods we now call genetic engineering, obviously calling it something else. He had experience and brilliance and this was how he managed to get the most out of animals he understood so well and the Torah , as the rabbis say, uses language that the common man would understand even if it is not exactly how he did it.
He succeeded to such an extent that as often happens in wealthy families, competition and tensions broke out between the son-in-law and the brothers-in-law. Jacob calls his wives out into the fields where they could not be overheard and told them that it was time for them to leave and head back to his parents and homeland.