It depends on how old a superstition is! In ancient times, people used to believe a lot in the supernatural and added explanations to some observations that they couldn't measure using their available tools at the time. A big example is about the sea monsters that were just whales or other different sea animals.
Even if we see the Bible, which is a very ancient book we have many things there that we don't follow anymore since we know better how the world works. I don't know much about superstitions in west Africa tribes, such as Yoruba, but for sure there are many things created to be cautious like you said for the time where it was created. As the same that we have some elements of the bible.
For example. The food restrictions to eating pork. We all know that pork is a meat that has a lot of parasites, so in the time that it was written they decided to create a rule to forbid it. Nowadays we know that cooking kills everything =)
!hiqvote
Exactly! It's all based on the time period. And they have endured through the generations, many of them turning into cultures for their people.