One thing about that, though, is that he left Ur and went to Haran, where he stayed some years with his mothers relatives. Remember that the Hebrews have always (as far as we know) figured descent as from the mother.
This suggests that it was not until the era of 1100-1300 AD that the present custom of requiring a Jewish MOTHER, not father...became the rule...and that this was in part because of persecution and scattering of small populations, declining literacy and moral standards, crime, rape, incest, leading to doubt as to who WAS the father, etc.