When reading about how some ancient peoples used to live, it seems clear that at every stage of historical development, there were codes of ethics, morality and civic duties which were part of society.
For example, in ancient Rome, the concept of marriage evolved from a matter of convenience to a moral requirement during the transition from republic to empire. So, the morality of late Roman pagan society blended well into early Christianity.
Throughout all this, morality continued to be viewed and taught among the populace via a series of myths. These myths have evolved over thousands of years of human experience. One can find such myths in every society from East to West.
Given that these myths are the product of millennia of human experience and knowledge, they continue to be valid today. Human beings of today have not evolved to be a lot different biologically from our ancestors from a few thousand years ago. We still face similar limitations in knowledge and understanding of ourselves, others and the world around us. As a result, it seems to make sense to study and understand ancient myths as these may give us insights about ourselves and the world around us.