If the link has a .gov or .edu it is always reliable. You can also look for contact information of the writer. If the person is a known pro then it could be reliable. Next you look at when it was posted, old websites tend to not have current true information due to the fact that every day there is something new learned by someone.
Hope this helps you find if the source is credible
I'd say something like cultural diffusion, because if he traveled to different places, so might of his customs and clothes. I'm not sure what else though.
