Question: Do you think that the fear of spiders lots of us have comes from the mesothelae spider that lived 300 million years ago. That could potentially injure the humanoids of that time.

Chris Werner answered on 17 Nov 2017:

Humans were not alive 300 million years ago, our species only really evolved 300,000 years ago! The reason the spiders were so big and you had millipedes the size of cars and metre wingspan dragonflies is that there was more oxygen during that time, about 30-40% of air!

Regarding the fear of spiders, that originates from the disgust element of your brain (hello Pixar’s Inside Out!) and back in medieval times, spiders were associated with spreading disease. For example, in the Middle Ages, any food that came into contact with spiders was considered to be infected, and if a spider fell into water, then that water was considered to be poisoned. Right up to the late seventeenth century, many European spiders were thought to be poisonous and to be causes of hysteria and symptoms of illness. So it appears to have come from that!