It’s obvious that scientists will attribute an innate fear of snakes and spiders to an “evolutionary origin”. Do they even begin to consider alternative, ‘metaphysical’, Jungian-type explanations?
The spider is an obvious symbol of the negative aspect of the Great Mother archetype, in her devouring aspect. Snakes also have a bad reputation, hence the Church’s decision to identify the serpent of Genesis with Satan. These are terrifying mythological figures, which explains humans’ innate reactions.
Our innate fear of spiders and snakes is better explained by Jung’s (metaphysical) understanding of the archetypes.