What's a traditional / archaic concept that actually happens to be right, just not for the reason originally thought?
I've been looking into feng shui lately, specifically the concepts about what makes a person feel more safe or at ease in a space, such as relaxing or sleeping facing the entrance / exit.
While reading, I came across the guidance that you should always shut your toilet seat to prevent your good fortune from being flushed. The real reason you should keep it shut is so it can't mist shit-water all over your toothbrush every time you flush. Also so your pets don't drink out of it.
What other things did humans throughout history accidentally get right?
I grew up on the coast, and my parents always had this rule to never eat/cook/serve shellfish that weren't fished (shellfished?) same day or yesterday.
Right, isn't that the point of the question? What old time things did we do for one reason (cloven hooves) that turned out to be right for completely different reasons (health and safety)
But I think it's at least as likely as not that whoever wrote that rule chose those buckets to be "unclean" because people got more sick more often. "I got sick once after eating it" is still one of the biggest reasons some people don't like seafood. Your brain is very good at turning single bad events into "don't touch this" if there isn't a body of safe interactions to fall back to.