So why do myths seem to persist despite their questionable veracity? I want to throw out a few thoughts about the lifecycle of myths:
1. Myths are interesting and tell a story that resonates with their audience. This helps get them in our brains in the first place.
2. Myths are credible, at least at first. Perhaps they are based on scientific argumentation or conventional wisdom or (somewhat limited) experience. This gives a myth a mental foothold.
3. Some myths are untestable, at least practically speaking from the perspective of people that believe them. So myth-based knowledge tends to linger.
4. Myths may be repeated (like memes) simply due to associative memory. People's brains work largely by association, so many myths spread because they give a person something interesting to say. This gives myths a way to spread.
5. To some degree, myths are busted for various reasons. But the overall dynamics of myths (call it myth epidemiology if you want) means that they may have already infected a significant portion of the population.
In order for Person A to efficiently disprove Myth X in Person B, Person A needs (1) to know that Person B believes Myth X; (2) to know and employ some action (such as a conversation) that will be effective; and (3) not have something better to do (opportunity cost).
Myths may simply be the knowledge "noise floor" of a world given the rate of new information generation and humanity's limited abilities to make sense of it.
