Virpi Lummaa’s group has another paper, Offspring fertility and grandchild survival enhanced by maternal grandmothers in a pre-industrial human society:
Help is directed towards kin in many cooperative species, but its nature and intensity can vary by context. Humans are one of few species in which grandmothers invest in grandchildren, and this may have served as an important driver of our unusual life history. But helping behaviour is hardly uniform, and insight into the importance of grandmothering in human evolution depends on understanding the contextual expression of helping benefits. Here, we use an eighteenth-nineteenth century pre-industrial genealogical dataset from Finland to investigate whether maternal or paternal grandmother presence (lineage relative to focal individuals) differentially affects two key fitness outcomes of descendants: fertility and survival. We found grandmother presence shortened spacing between births, particularly at younger mother ages and earlier birth orders. Maternal grandmother presence increased the likelihood of focal grandchild survival, regardless of whether grandmothers had grandchildren only through daughters, sons, or both. In contrast, paternal grandmother presence was not associated with descendants’ fertility or survival. We discuss these results in terms of current hypotheses for lineage differences in helping outcomes.
The basic finding is that in Finland maternal grandmothers increase the fitness of their grandchildren. This is a big finding in Lummaa’s work but in the discussion this paper notes in other cultures a paternal grandmother effect may be operative. So how general is this result? Do we believe in the maternal grandmother effect?
Also, despite the possibility of a maternal grandmother effect, societies in the last 5,000 years seem to have shifted to strong patrilocality and patrilineality. Is this a multi-level selection problem? Basically, inter-group competition between groups hash out so that patrilineality wins on that scale, but within the groups, maternal grandmothers are more important?
In pre-industrial societies most people married within their own village or neighborhood. So in most cases maternal grandmothers lived nearby if not right next door. Maternal grandmother is qualitatively different from paternal grandmother for being the mother of mother. In pre-industrial societies mothers spent much more time with children than fathers did and were the people primarily responsible for raising children. Thus being the mother of mother, maternal grandmother would feel more affiliation with mother than did paternal grandmother and feel more drive and responsibility to help mother raise her children. But in highly patrilocal contexts in which paternal grandmother and mother lived in the same household, probably paternal grandmother would spend much more time helping mother raise her children than whatever maternal grandmother could do. So I do not think the results of this paper can be generalized to all pre-industrial contexts.
My wife was not working, so she went to her mother’s place after birth of first child & my son was effectively brought up by his maternal grand mother
For 2nd child, since son was studying here, she opted to give birth here itself & not in her mother’s place
In pre-industrial societies most people married within their own village or neighborhood.
this is bullshit. you don’t know this, you assert this.
north indian hindus traditionally practiced village exogamy for example
But in highly patrilocal contexts in which paternal grandmother and mother lived in the same household, probably paternal grandmother would spend much more time helping mother raise her children than whatever maternal grandmother could do. So I do not think the results of this paper can be generalized to all pre-industrial contexts.
there has been work done in bengalis, who are very patrilocal, that despite the norms maternal grandparents are still more important. in contrast, the nearby khasi have norm/practice alignment (matrifocal)
this is bullshit. you don’t know this, you assert this.
north indian hindus traditionally practiced village exogamy for example
I did not state that all pre-industrial societies were like that, I am talking about the majority.
there has been work done in bengalis, who are very patrilocal, that despite the norms maternal grandparents are still more important. in contrast, the nearby khasi have norm/practice alignment (matrifocal)
This is interesting. Would like to hear more about that Bengali study.
What’s the mobility of old ladies like in such societies? I’m guessing it’s probably not very high. But it seems if maternal grandmother presence is useful (more useful than her being another mouth to feed, offsetting food availability for kids) and societies are otherwise patrilocal in organisation, then it seems like a ‘rational’ compromise solution is simply for old ladies to move to where their daughters of childbearing age are living.
“it seems like a ‘rational’ compromise solution is simply for old ladies to move to where their daughters of childbearing age are living”
What if their daughters have moved to different places?
@TGGP, yeah, I don’t know how much that happens. Completely open question. I don’t think it’s totally solvable (if your culture has extensive village exogamy and preferred partners not usually from same external village), but you could possibly adapt to optimize to some degree under many conditions.
What if their daughters have moved to different places?
They can prefer to stay with the daughter with the youngest kid or can rotate between the daughters’ households giving priority to the ones with the youngest kids.
Grandmothers themselves had their own household to run and weren’t free to move to their daughters household.
My grandmother had her first grandchild two months earlier than her own last child. It’s not like grandma was free to go to each of her six daughters houses. (Often cousins happened in close age groups). Grandma and two of her sisters all had their first and second children in the same year, and of course at their maternal home.
In South India, typical ritual was for the brother of first-time pregnant lady to formally request the in-laws to send his sister with him. This happens in second trimester and usually new mother returns with the baby after the first two or three months. Therefore, the pregnancy/ new baby rituals (like baby shower, putting newborn in a cradle, first bath) etc involve a lot of maternal relations in South India.
Typically this happened when the villages are within a day of travel and bullock carts are typical travel means. (It is a thing/to-do when a first-time pregnant lady arrives in decorated bullock cart to her maternal home).
Even today, it is taboo to even eat at your daughters in-laws house. The belief is that it would lead to break-up of the girl’s marriage.
Was that really the case – even with “the majority”? I grew up in a highly exogamous (East Asian) culture that was so terrified of inbreeding that it was illegal to marry someone with the same surname, no matter how distantly-related, a practice that has been carried over from pre-industrial days. For that matter, many Central Asian nomads (including, famously, the Mongols) practiced bride-kidnapping, which – it appears to me – to have had a strong outbreeding intent.
Meanwhile I remember reading years ago a petition made by a retired Roman centurion, who, in reciting his personal history, lineage, martial valor, mentions that his brother gave him a daughter (his niece!) as a wife.
I think the whole endogamy/exogamy issue is not so cut and dry. And practices varied considerably by region and culture. Of course, the farther back in history we go, we are likely to find more inbreeding and endogamy of all sorts.
If you have evidence supporting what you wrote, I’d appreciate reading it
I’m not surprised to see this correlation, but I worry about confounds. If something killed the grandmother before she got old, it’s probably also affecting the grandkids pretty negatively. And even if the grandmother is alive, she might have several daughters but chooses the richest one to live with (more room there, nicer place). The rich daughter’s kids have better outcomes, no duh, but maybe not because their grandmother lives with them.
@Twinkie
Mine is just an inference based on my knowledge about the residence and movement patterns in pre-industrial societies. There are not enough stats to give a conclusive answer on this issue to my knowledge.
Central Asian nomads are a very different case since they did not live in permanent settlements and were highly mobile.
Central Asian nomads weren’t wandering vagabonds. Their tribes had territories and they were “nomadic” to the extent that they generally moved between summer and winter pasturage. Moreover pure nomads were rare (and small in number, necessarily) and groups such as the Mongols were semi-nomads who lived in that zone between the settled and the truly nomadic. They traded with the settled people and without the grain of the latter (among other goods), they wouldn’t have had enough population to become powerful and threaten settled states (even with a much higher mobilization rate, there is a limit to the size of armies if the overall population is too puny).
And even some settled Central Asians and agricultural East Asians practiced exogamy and didn’t marry their neighbors who were likely to be their kin.
In any case, you would think that high mutual mobility would reduce chance encounters among tribes and actually increase endogamy rather than reduce it. But for some cultural reasons, that wasn’t the case.
Then you shouldn’t write such conclusive statements.
This paper is interesting on inbreeding and exogamy in Central Asian Turkic and Mongolic groups (comparison to Tajiks): https://www.nature.com/articles/s41598-018-27047-3?proof=t – Close inbreeding and low genetic diversity in Inner Asian human populations despite geographical exogamy
We collected ethno-demographic data for 1,344 individuals in 16 populations from two Inner Asian cultural groups with contrasting dispersal behaviours (Turko-Mongols and Indo-Iranians) and genotyped genome-wide single nucleotide polymorphisms in 503 individuals. We estimated the population exogamy rate and confirmed the expected dispersal differences: Turko-Mongols are geographically more exogamous than Indo-Iranians. Unexpectedly, across populations, exogamy patterns correlated neither with the proportion of inbred individuals nor with their genetic diversity. Even more surprisingly, among Turko-Mongols, descendants from exogamous couples were significantly more inbred than descendants from endogamous couples, except for large distances (>40 km).
@Twinkie
What I mean to say is that nomads did not have settlements that existed throughout the year; they lived as communities where their tents were pitched at a particular time. Of course their summer and winter pastures were in fixed locations in general. They indeed had symbiotic or parasitic (depending on the circumstances) relationships with the sedentary communities around them and were dependent on them, but this is a separate topic. They tended to be exogamous like you point to.
@Matt
Yes, I know that paper. The results are a mixture of different cultural backgrounds (Iranic vs. Turco-Mongol) and traditional living styles (sedentary vs. nomad). We see this most clearly in the marriage patterns and genetics of Uzbeks and Uyghurs, who are Turkic but traditionally sedentary and have the Turco-Mongol exogamy but also the sedentary higher genetic diversity.
This makes me wonder about the mechanism of causation and the direction of the said causation.
@Twinkie
This makes me wonder about the mechanism of causation and the direction of the said causation.
Well, if more of descendants from exogamous couples are from the traditionally nomadic Turco-Mongol groups than are descendants from endogamous couples, that may explain it, at least partially.
In the modern context maternal grandmothers help the daughter more, since the relationship between grandmother and mother is more intimate. In the past, in patriarchal-patrilocal times, the same role was offered by the mother in law on a similar level, while the maternal grandmother was not present.
If the mothers have the choice, they usually prefer the help and interference of their mother, rather than their mother in law, but ina structured, well-organised patriarchal society, that choice was not present and it worked out too.
However, I would not overestimate the grandmother effect in general, because for many parents in the past, their own parents were dead anyway, far away, or could not help all the siblings at once.
All these studies concluding from the modern, chaotic conditions to the well-organised past are inconclusive, because they assume a degree of individual choice which was
– not present
– is not natural for the human cultural species.
Humans function, especially in their reproductive sphere, the best in a limited, structured and predetermined environment. Whenever the familiar structures broke down to a more primitive and chaotic level, things got more messy and the birth and survival rates no better. Late Rome might serve as an excellent example, in which the structures turned upside down as well and many unmarried mothers lived with their parents, instead of moving to the husbands house.
The Western family structures are completely dissolving, getting amorphous and dysfunctional.
Any kind of study, especially on birth rates and negative selection, done on people living the current Western way of life are not necessarily meaningful for the situation of the past. Because if the past would have worked the same way, there would be no present.