> Someone who's afraid of a specific thing, however, cannot transmit fear of that specific thing unless there's some incredible and unexplored cognition-to-biomolecular signalling mechanism that's entirely unexplored and undescribed.
While there is absolutely no conclusive evidence, there are a few studies that indicate this is a possibility.
But if, evolutionarily, there are only 20 common recurring threats that you need to fear (but each comes at some kind of cost, like you won't hunt in an area that would otherwise provide food), it would make sense to pass on those fears in a generational way. So the possible things come from a preset list that has evolved over millions of years, that recur over and over but only in specific times and places.
While there is absolutely no conclusive evidence, there are a few studies that indicate this is a possibility.
One such study from 2013: https://www.nature.com/articles/nn.3594
Again, there’s not strong proof- but at least plausible evidence.