In Genesis 16 there’s a fragment that caught my attention, which might support the hypothesis that Abram came from a matrilineal society in the middle east.
His wife, who is his half-sister Sarai, is marriageable because they have different mothers. Different mothers means different clans and this is therefore a legal union. Marrying Sarai was not incest in matrilineal society. Here again is the family tree to support this:
In Gen 16:2 Sarai tells Abram to sleep with her Egyptian handmaiden Hagar and adds, “‘It might be that I am built up by her.’” We see this same system among the Romans, Greeks, and Hindus, except within a patrilineal framework: a man may give his wife to another man temporarily, or a father may force his daughter to take a different man temporarily, so that a male heir is born.
In a matrilineal society, as in Sarai’s case, we would assume that Sarai is seeking to have a female heir through Hagar. But instead, Hagar has a male, Ishmael. This would mean that Sarai’s clan marker (or token) will end, since in a matrilineal society Ishmael would then go off to marry a woman of a different tribe and have children who would bear HER clan marker.
However, an angel promises Hagar that her seed will be “‘too numerous to be counted’” through Ishmael. Robertson Smith’s Kinship and Marriage in Early Arabia makes a good case that ancient Arabia, which the Quran traces through this same Ishmael, was originally matrilineal. Each clan had its own totem like “Badan” which was an ibex, “Bakr” the he-camel, “Tho’Al” for fox. One clan totem which stands out is the “Yaghuth” clan which means “lion”. This appears to be a cognate of “Yahuda” or “Judah” whose ensignia is also a lion. These clans intermarried and mixed their totems together in each marriage alliance, producing the polytheism that Mohammed decries throughout the Quran.
My theory is that patrilineal systems can only emerge once fortified cities can be built up through agnatic, father-to-son inheritance, and maintained with sufficient metallurgical technologies like iron. Bronze appeared to be inadequate due to its swords losing an edge too quickly and resulting in too much emphasis on “poking” arts, a very difficult skill to teach a standing army according to Oakshott in The Archaeology of Weapons. Robert Drews’ The End of the Bronze Age makes the case that the “Naue Type 2” sword, when it was made from iron, could be swung freely in a hack-N-slash fashion, which was the death of chariot warfare and therefore the end of the Bronze age.
Islam is one such phenomenon, though a late one: Arabia’s transition into a patrilineal society which eliminated polytheism. You also get written languages this way, since you lose all the mixing of dialects in a matrilineal system and move into a stable empire language.
(Leonard Shlain’s theory in The Alphabet Versus the Goddess that alphabets somehow naturally emerge in advanced societies starts on the wrong foot. You first need a transition to patrilineal descent. Then you can have writing, monotheism, large standing armies, etc. None of these are neurological developments as Shlain might claim. They’re simply byproducts of patrilineal society.)
Ishmael cannot be an heir to a woman in a matrilineal society, so this would have been catastrophic to the elderly Sarai, who is I believe 87 at this time since Abram is 86. This is all clear evidence that Abram’s society is matrilineal.
In the next chapter, Genesis 17, Abram is 99 years old and is given a son, Isaac. Only then does he become “Abraham.” The best and clearest difference between Abram and Abraham was that Abram lived in matrilineal society, while Abraham is the beginning of patrilineal society. He is at the transition, much as Mohammed was in the Quran.
A followup question would be: how much of the subsequent patrilineal society depicted in Genesis is fictitious? Isaac’s story is short, mostly copied from Abram’s, and after the aborted sacrifice Abraham returns to his donkey without any mention of Isaac. Tsemah Yoreh’s theory in Why Abraham Murdered Isaac is that Abraham actually killed Isaac. I think there’s another possibility here (which will be totally heretical to most): Isaac is a fictitious character who merely bridges Abraham to Jacob. Judah traces its lineage through Jacob, and so to have a legitimate claim to Israel, it needed a connecting point to Abraham, and Isaac fulfilled this.
Of course I’m very, very happy to be wrong about this, but this is a much cleaner explanation of the text than anything else I’ve read.