Forgive my limited biological knowledge. How is it that certain instinctive traits are passed on in dogs (and, presumably, other animals)?
Allow me to explain. With purebred dogs, breeders spent hundreds or thousands of years carefully selecting certain physical and behavioral traits. I understand how physical traits are inherited, but don’t get the behavioral part.
Let’s take German shepherds. My sister has one, and although he has now decided that playing ball is his job, he does, on occasion, herd things. Usually the cats, which I saw him do the other night, and also children. He has been raised in a suburban home since puppyhood, so he has no prior experience in a pastoral setting. Presumably, the herding behavior he exhibits is instinctive.
Nobody know how instinctual behaviors are stored in the brain. However, humans select for behavioral traits in dogs the same way they choose for physical traits. The most basic example is that dogs themselves were bred from wolves by selecting the wolves that were less timid around people and were willing to approach in a non-violent manner. The wolves that had the best examples of these traits were bred to create the new generation with these traits. Repeat. Repeat. Repeat.
The idea is same for almost all instinctual traits. If you want to create a herding bred, you start with a breed that has traits needed for herding like intelligence and high energy. One generation at a time, you select the puppies that are a little closer to the desired traits and proceed with those to breed again. Over many generations, this type of selection will hopefully lead to a new breed with the desired traits with few undesirable traits or health issues.
I don’t think we understand the genetics of instinctive behavior. You should note, however, that even in breeding sheep-herding dogs, the breeders will identify the ones which are best at herding early on (ie, the ones which have the strongest instincts) and then train them further. The ones that don’t pass muster are destined to be just pets, not working dogs.
If you accept that physical traits are inherited, then you accept that the DNA contains a complete blueprint of the body - the structure of each organ, and the way they are all connected. Is it really a stretch to think that the structure of the brain itself is also stored and inherited the same way? The way the neurons are connected to each other, so it responds a certain way to stimuli?