Historical questions about God and the Bible

I think the belief that some Arab tribes were descended from Ishmael already existed before Mohammed but I don’t know exactly how old the belief is. It’s probably safe to say that virtually all Muslims believe that Arabs are descended from Ishmael and that Abraham was a historical person. It isalso true that some non-Muslim Arabs believe that. It cannot be said that all non-Muslim Arabs believe it. There is such a thing as secular and atheist Arabs.

Exactly. I just wanted to know if the lineage is considered a secular belief established pre-Islam or a faith belief. Islam considers Arabs descendants of Abraham/Ishmael but not all Arabs believe in Islam or other faith based beliefs rooted in the bible or Koran. It is not Muslims, as I stated, who trace their lineage to Ishmael. It is Arab Muslims or Christian Arabs but not all Arabs.