I was listening to a psychologist a while back who said that nature has developed and reinforced the fear of heights for our species survival . If we stand at the edge of a cliff, we need to protect ourselves so adrenaline kicks in, the ‘Fright’ part, to stop us there before taking action or to back away. Same with being at the top of the tree.
Apparently we are physically connected to the ground (safety) through our senses - we see the potential problem, but we feel the solution because we still keep our feet on the ground/tree keeping us based. This has been passed through the generations for ever.
BUT , flying (not falling) has not been implanted in our DNA as unsafe, as it is not a naturally occurring situation. Children won’t be afraid of it as it only becomes a learned fear, through their own experience or relayed information from others.
It was an interesting article
Ken