system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is claustrophobia such a common fear, given that our ancestors were cave dwellers? Wouldn't we have adapted to tight and dark spaces?
gpt
Although prehistoric humans are often called "cavemen" its likely that the vast majority of early humans did not live in caves. Caves are where we find most prehistoric human artifacts, but that's because caves preserve things that would be destroyed, lost, or buried outside.

It's far more likely that most humans lived in things like tents and huts. Keep in mind that prehistoric humans had the same intelligence as you or I, and so were perfectly capable of constructing simple shelters.

Also, you assume that fears like claustrophobia are hereditary. That's far from clear.