This reminds me of an article I read on fear & learning in monkeys a while ago.
Basically, monkeys aren't born with fear of snakes; they only start fearing snakes when they see another monkey fearing snakes.
However, if a monkey sees another monkey fearing, say, flowers... the only thing that that monkey learns is that some monkeys are crazy.
The conclusion of the article was that fear of snakes and other dangers were instinctive & genetic, but it was dormant by default and had to be "triggered" by external stimulus before it could be expressed. This fits in with a lot of genetic-influenced behavior we see (e.g., alcoholism; little kids don't steal from their parents' liquor cabinets--they have to take their first drink before becoming alcoholic).
Perhaps it was this reference in EDGE to a 1988 study by Susan Mineka:
The classic and best experiment in this is Susan Mineka's work with a group of monkeys in Madison in the '80s, where she set out to examine the ontogeny of an instinct—in this care fear of snakes.
Wild-born monkeys are afraid of snakes. They're so scared of snakes that they will cower in the back of the cage screaming rather than reach across a plastic model snake to get at a peanut when they're very hungry. Captive-born monkeys are not afraid of snakes; they happily reach across the model snake to get at a peanut.
So what's going on here? That means that fear of snakes must be learned. But how on earth do you learn fear of snakes? The conventional classical conditioning wouldn't work very well, would it, because either you have a bad experience with a snake to learn from, in which case you're dead, or you don't have a bad experience, in which case you don't learn that snakes are frightening.
So how are you going to end up acquiring a fear of snakes? It seems an absurd thing to acquire. She argues that what's happening is that there is a program for fear of snakes, an instinct if you like, but that that instinct needs to be socially triggered—in some sense triggered by a vicarious experience, by observing another monkey having a fear of snakes. So she set up an experiment in which she videotaped the wild-born monkey reacting with fear to a snake, and she then showed this video to a captive-born monkey, which immediately acquired a fear of snakes and was not then prepared to reach across even a model snake to get a peanut.
She now doctors the video, so that it has the same monkey reacting in the same way in the background, but the bottom half of the screen now instead of having a snake has a flower. Again, the captive-born monkey has never seen a flower, so after it sees a monkey reacting with extreme fear to this new thing called a flower it should just as easily learn a fear of flowers. But it doesn't. It just learns that some monkeys are crazy.
So what's going on here is that there is clearly an instinct for fear of snakes, and that's not surprising. Human beings have snake phobia. It's the commonest of all the phobias, even though most of us hardly even ever see a snake in our lives, but it requires an input from the environment. It requires a nurture input to be triggered. We know this is happening in the amygdala, and we're getting a bit of a handle on which cells are involved. We're not yet down to the gene level, but I'd bet my bottom dollar there's going to be a little pathway of genes in here that's mediating this process.
From EDGE: http://www.edge.org/3rd_culture/ridley03/ridley_p5.html