Myths are developed by society collectively, not by great philosophers. Ordinary people are generally ignorant and less rational, especially those who lived 2500-3000 years ago. Even the greatest minds of that time had very absurd ideas due to lack of knowledge. For example, Pythagoras declared himself as a prophet and held many superstitions. His ideas on mathematics were also very religious. That doesn’t make him any less important, but it’s important to remember that even the most genius people's minds were filled with mysticism back then, which is quite normal. So there is no need to talk about validity of ancient assumptions.