I first encountered the concept of matrilineal social structure in a fantasy novel I read while stranded in the middle of Iowa following a car crash in 1977. The title has escaped my memory; I remember it as being rather clunky, but the only book I had during the six hours I was stranded. The presentation of matrilineal culture wasn't very effective, though, and I was left with the impression that it would never work, as least as presented, in the real world.
The concept came up again recently during a discussion of Arthurian Romance, and while it still struck me as difficult to sustain as presented, I also realized that our historical knowledge of matrilineal cultures has pretty much invariably been filtered through the mind of an observer who was steeped in patriarchal culture, and that was likely to color things.
All of this resonated in my mind, and eventually collided with the Lion Problem (defined in a moment), and I started doing some serious speculation about the nature of a functioning matrilineal, or even matriarchal, culture given human reality. Please note that all of the following is off the cuff; I haven't as yet cross checked any of against historical records, only against what is already in my head.
First, though, a bit of a digression, referred to a moment ago as "The Lion Problem". It really isn't a problem, at least for the lions. It's just that I am amused and bemused that lions have managed to develop a social structure which is absolutely genetically superior to that of modern humanity. Now, it was believed until the latter half of the 20th century that lions were patriarchal, largely because most of the observations of lions in the wild were made by arrogant male Europeans by daylight. Eventually a different pattern came to light, though.
Lions are absolutely matriarchal. Yes, prides consist of a single adult male shared by several adult females, but that doesn't really mean anything, once you understand the entire life cycle. Adolescent males are driven from the pride and forced to survive on their own, competing with the individually inferior but pack oriented hyenas. When a pride's patriarch dies, the pride member go looking for the oldest solitary male they can find; the perfect candidate is one that is just short of falling prey to the hyenas, but still sexually functional. The pride adopts him, keeps him alive, uses him for sex, and pretty much goes on with business as usual. So yes, the pride DOES have a patriarch, but the females are firmly in control.
The genetic advantages of this are pretty clear. Given the rigors of childbirth, it is impractical to select for longevity on the female side. On the male side, however, an otherwise healthy male can father children at any age. All sorts of survival traits are selected for on the male side while childbearing females are protected. It's a great system if you are female, or a male who has survived long enough to become a patriarch. It is rather hard on the other males of the species, though.
Now, back to humans and matrilineal cultures.The first obvious thing is that marital fidelity (thought not necessarily marriage) is a non-issue in such a culture. If a woman is an accepted member of the community, her children are also accepted members of the community, regardless of who fathered them. Marriage in such a culture would be a matter of establishing the place of men in the culture, and only that. So matrilienal cultures will almost certainly matriarchal oligarchies, if not just matriarchal.
The problem is that, without some additional controls, female dominated societies are inherently unstable. Human males have a 4 to 3 edge in body weight, and an even greater edge in overall musculature, and if numbers are equal, all it takes is one dissatisfied and charismatic male, and the men will revolt and seize control. So for a female dominated society to be stable, it needs something to keep the males down: Metaphorical hyenas.
(As an aside: Some polygamous patriarchal cultures managed to get some of the advantages of the older male/ younger female pattern by reducing females to chattels, establishing bride prices that only rich men could afford, and keeping the unmarried male population in check by widespread ritual prostitution. Given a choice between reducing women to chattels, and killing off two out of every three males, I tend to prefer the bloodbath. But that's just me.)
In the early days of civilization, an isolated village (or a network of isolated villages) could do nicely by following a practice very similar to that of the lions: Chasing out adolescent males with instructions to never come back. Males who survived to find other villages would then be accepted. This would work as long as the process of finding the next village had a mortality rate in the 50% to 80% range; outside of that, you end up with either too few men, or too many. And as civilization progressed, and trade and travel became easier, the mortality rate of the process would invariably fall to unacceptably low levels.
This requires other, more sustainable methods of keeping the male population in check. Infanticide works, and has been practiced; the documented practice in some cultures of sacrificing the first born male child of every woman would do a tolerable job of keeping of balancing the population to make a matriarchy sustainable. Frequent small but bloody wars would also work, as would a culture which encouraged frequent fatal duels.
Obviously, there is a lot of ground for speculation here. Also a lot of room for research I haven't done yet. But I am really intrigued by the fact that there seems to be an historical connection between the concepts of marital fidelity, and women as chattels. Who'd a thunk?