Much of Galen’s knowledge came from Ancient Egypt. The genius who started their medical college (as well as built the first pyramid and invented mummication was Imhotep—Vizer to Pharoah Dozer. (they were also drinking buddies)). He was a commoner, believed to be the smartest man in Egypt. Over the centuries they emassed a huge number of medicines and cures. We still do not know all they discovered—such as Leprosy—the scourge of the ancient world—was unknown in Egypt? Why?
And if I remember correctly Pharoah Dozer was over 4,000 years ago. Are you sure that there was no Leprosy in Egypt? I was just reading Leviticus the other day and there were a lot of details on how to test for Leprosy and what to do if it was discovered.