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?
Alice Dreger has a remembrance of Napoleon Chagnon in The Chronicle Review. This part jumped out at me:
The reason he was willing to work with me for over a year was not because he had a big ego — which he did. It was because he knew the “closest approximation to the truth” would exonerate him. He knew that Tierney had misrepresented so much.
…
The chair of the AAA task force knew it too. That was Jane Hill, former president of the AAA. During my research, Sarah Hrdy shared with me a previously confidential message, dated April 15, 2002, in which Hill responded to Hrdy’s concerns about the task force’s work.
“Burn this message,” Hill told Hrdy. “The book [by Tierney] is just a piece of sleaze, that’s all there is to it (some cosmetic language will be used in the report, but we all agree on that). But I think the AAA had to do something because I really think that the future of work by anthropologists with indigenous peoples in Latin America — with a high potential to do good — was put seriously at risk by its accusations, and silence on the part of the AAA would have been interpreted as either assent or cowardice. Whether we’re doing the right thing will have to be judged by posterity.”
It’s easy to understand the calculation Hill and others were making.
If you don’t know, the backstory is around the year 2000 the anthropologist Napoleon Chagnon came under fire as having aided and abetted genocide in the course of his research in a fashion that would make Josef Mengele proud. On the whole, all the accusations were false. But until that was established Chagnon came under fire from colleagues, and members of the press. The New York Times Book Review gave the critique of Chagon a positive review, something which John Horgan does not seem to regret much.
Despite the storm and fury ultimately the whole episode came to a just conclusion: Chagnon and James Neel were exonerated. The AAA task force report was eventually rescinded.
Does anyone believe that if the same thing happened today in 2019 it would end in the same way? I don’t think it would at all. The accusation itself would have destroyed Chagnon’s career immediately. Associates and colleagues would have been called upon to denounce Chagnon. Silence would be seen as suspect.
Perhaps people would understand on some level that it was far far better that one individual’s reputation must die so that the field might live. But whereas in 2000 those who were making this calculation seemed embarrassed about what they were doing, today I doubt there would be such reluctance. Even if Chagnon and James Neel were not guilty of the specific crimes, they were born convicted in the eyes of critics as white males. The only way that it would work out for Chagnon today is if he turned on Neel and denounced him, sacrificing the dead for the living. A “struggle session” would be his only defense.
We all know this is true. I suspect this is why Horgan seems utterly unashamed about having given praise to a book in 2000 which aimed to destroy reputations but which we now know as false. By today’s standards what he did was not a big deal. Sometimes you have to break a few eggs to make an omelet.
One of my favorite quotes is from the Roman playright Terence. He asserted: Homo sum, humani nihil a me alienum puto. I know of it through the English translation, “I am human, and I think nothing human is alien to me.”
This truth was brought home to me in the early 2000s when I read Scott Atran’s In Gods We Trust: The Evolutionary Landscape of Religion. Atran has a long section where he critiques a dominant mode of analysis and interpretation within American cultural anthropology which emphasizes differences in cognitive frameworks and paradigms, to the point of incommensurability. The simplest reduction of Atran’s critiques are that the logical conclusion of this line of thinking would make even the interpretive scholarship of this school of cultural anthropology totally worthless.
A more concrete issue where this form of thinking has crept into the broader discussion is confusion of terms for reality, and the reconceptualization of reality through diversification of terminology. Consider the discussion about democratic forms of governance. One can assert, with credibility, that the Greeks “invented” democracy. But, I think this masks the reality that the democratic impulse existed across many cultures and societies (e.g., the republics of ancient India). The Greeks had a genius for systematizing and formalization of social and political structures. But the basic elements and dynamics were already there.
Similarly, people are wont to say that one can’t understand Chinese or Indian religion from the Western perspective of religion. I understand where people are coming from when they say this (and in fact, it’s not a “Western perspective,” but often a post-Calvinist confessional Protestant conceptualization that they have in mind as “Western”), but the reality is that the broader category of religious phenomena is easy to identify. That is the reason that Portuguese Catholics initially though Indian Hindus were Christian. It is the reason that the Chinese and Japanese in the 16th century often confused Roman Catholicism with a sect of Pure Land Buddhism. Religions differ a great deal across cultures. But they are pretty recognizable.
But there is the reverse side to this equation: thinking that you understand the psychology of others so well that you misconstrue their motives and intentions.
Two concrete examples come to mind. My liberal friends often talk about conservatives in ways that seem totally wrong-headed, but, they behave as if they understand the conservative mind as experts, despite not knowing any conservatives besides myself or reading much about conservatives in a way that takes ethnography seriously. There is some evidence that liberals, in particular, have problems modeling conservative motivations, but the issue is general and not specific to any ideology.
To illustrate this, on the Say Goodnight Kevin YouTube channel, there is an analysis of Christian* films and media from a skeptical perspective. Kevin himself is an evangelical Christian who was homeschooled. One of his major criticisms is that in evangelical Protestant Christian media nonbelievers, especially atheists, are depicted in a way that is totally unrealistic, and in keeping with the prejudices of evangelicals about the low moral character and motives of nonbelievers.
Obviously, there is a spectrum here. Humans are not total islands from each other. The limits of my comprehension are not the limits of my culture. But neither are cultural and subcultural norms and idioms so transparent that one can always make very precise and deep inferences about the intentions of outgroups. Any analysis of human psychology and culture must always wrestle with this reality.
* “Christian” here refers to the American evangelical Protestant subculture.
Though we are taking a hiatus for the summer for The Insight podcast, we have many episodes already recorded and ready to go. The current plan is to launch season 3 with a discussion between Spencer and myself on the Tocharians.
One of the things I brought up is an observation about the changing lifestyles of proto-Tocharians and post-Tocharian peoples. It seems likely that the proto-Tocharians, the descendants of the Afanasevio people, were pastoralists. At some point, they settled down in the oases around the Tarim Basin. And, they became city-dwellers. Eventually, they were conquered by the Uygurs. They too were pastoralists, and they settled down to become city dwellers. The Uygurs were eventually conquered by other Turks, who also became city dwellers.
To my knowledge, the shift from pastoralism to a sedentary lifestyle seems to be far more common than the other way. Pastoralist peoples conquer sedentary peoples…and in their turn settle down, and are conquered by later pastoralists. Meanwhile, hunter-gatherers, such as Mongolians and Australian Aboriginals, adapt to pastoralism quite well.
Australian Aboriginal child photographed in the late 1850s
The above chart is from The Simons Genome Diversity Project: 300 genomes from 142 diverse populations. The basic outlines of this tree were evident as far back as L. L. Cavalli-Sforza. But there were always small details that caused issues. In particular, were East Asians a more natural clade with Australasians or with Europeans? Today with both ancient DNA and whole-genome analyses two things are clear which might have been confounding earlier analyses:
There has been gene flow between many East Asian and European populations. If you look closely at the ancient DNA work it is clear that East Asian gene flow is present in Mesolithic hunter-gatherers. Conversely, many northern Chinese have show low levels of West Eurasian ancestry (I suspect mediated through Mongols and Turks).
The peoples of Australasia have Denisovan ancestry, which is distinct from anything found in East Asians and Europeans (small trace proportions of Denisovan in the former notwithstanding).
With these considerations accounted for, it seems clearer that the peoples of Oceania and East Asia descend from a common group that pushed from the west. And, the most ancient substratum in South Asia is also part of this broad family of peoples, who diversified in the period between 45 to 55 thousand years before the present. This is in contrast to the peoples to the west, who gave rise to Ice Age Europeans, Middle Easterners, and more distantly the “Ancient North Eurasians” who seem to be the first settlers of Siberia.
To understand the context for the emergence of characteristics and traits one has to understand the demographic histories and relationships between people. We are coming close to establishing the latter with good certainty for most groups. Though the sea levels separated New Guinea from Australia only within the last ~10,000 years, genetic work suggests that the differentiation between highland Papuans and Australian Aboriginals long predates this. If I had to hazard a guess I’d suggest that the huge ecological differences were probably critical in reducing gene flow between the wet and warm highlands of Sahul, and the broad deserts that occupied what became Australia.
The above map is from a new preprint, The Origins of WEIRD Psychology. If you don’t know, WEIRD refers to “western, educated, industrialized, rich and democratic.” And, it focuses on the problem that so much of psychological research has been done through surveys and experiments on university students, who tend to be from the more privileged half of developed societies in the West.
Despite the title, this preprint is less about the particularity and distinctiveness of WEIRD psychology subjects, but rather the socio-historical and cultural context from which WEIRD has developed. From the abstract:
We propose that much of this variation arose as people psychologically adapted to differing kin-based institutions—the set of social norms governing descent, marriage, residence and related domains. We further propose that part of the variation in these institutions arose historically from the Catholic Church’s marriage and family policies, which contributed to the dissolution of Europe’s traditional kin-based institutions, leading eventually to the predominance of nuclear families and impersonal institutions. By combining data on 20 psychological outcomes with historical measures of both kinship and Church exposure, we find support for these ideas in a comprehensive array of analyses across countries, among European regions and between individuals with different cultural backgrounds.
The hypothesis itself is not entirely novel. I first encountered the argument that the Western Church was critical in eliminating the familial strategies used by Late Antique Roman elites to maintain their power and wealth in Adam Bellow’s book In Praise of Nepotism. This preprint outlines the exact process which Bellow described: the Western Church constrained and limited the pool of possible mates through incredibly stringent incest regulations, as well banning adoption and other ways to prevent lineage extinction. Bellow presents an almost materialist thesis, whereby the Western Church consolidated its power and wealth through regulating the personal lives of Western Europe’s ruling elite. By destroying powerful pedigrees not only did the Church eliminate a temporal rival, but often the wealth of these elite lineages went to the Church if there were no heirs.
I’ll get back to the history in a bit. But first it has to be admitted that formalizing and quantifying these patterns is the value of this preprint. It would be easy for me to critique a particular set of variables, but there are so many, and they did so many robustness checks, that it hard to deny that the authors picked up some signal in the data. Probably the most persuasive aspect is that some of the signals persist within countries. That is, areas subject more to Western Church coercion for longer periods exhibit reduced kinship intensity down to the present. In most of the world lineage groups and familialism were and are much more pervasive and powerful than in the medieval West, where non-familial organizations such as guilds and monasteries stepped into the gap. What we might call “civil society” or the “small platoons.” These became “high trust” societies, and set the stage for the cultural and economic revolution of early modernity, from science to industrialization and the flourishing of democratic liberalism.
There have been many debates about why Europe underwent lift-off after 1500. Some of the models rely on exceedingly simple causes, such as the discovery of the New World releasing parts of Atlantic Europe from Malthusian pressures, as well as the location of coal in accessible regions of England. It seems possible that a single necessary and sufficient cause does not exist. The combination of the European discovery of the New World, along with their relatively open and high-trust societies engendered by the dissolution of extended clan structures by the Western Church was likely a potent cocktail.
In any case, I want to revisit the issue of how and why the Western Church went the route that it did. Because Christians in other parts of the world did not reform family structure in the say way. As hinted in the preprint, it may have to with the fact that the collapse of the imperial order in the West resulted in the devolution to the Church certain powers that would otherwise have been accorded to the state. In the lands of post-Roman West local bishops had the power of princes. Even the Pope in Rome took the role of a prince on more than one occasion. But, they also had the power of religion, which for all practical purposes was magic. To make a nerdy allusion, the bishops of the post-Roman world were both Aragorn and Gandalf in one. They were priest-kings.
The same did not hold in the East Roman Empire. Though the Eastern Orthodox Churches have often clashed with rulers, they were much more subordinate for all practical purposes than the Western Church. The East Roman Empire maintained the bureaucratic function of the Roman world down to the medieval period. In contrast, much of the apparatus of state control withered in the post-Roman West, as it devolved into feudalism. The Western Church maintained the cultural connection with Romanitas in the West in a landscape where the authority of Rome had vanished. That cultural connection was channeled through Christianity, where marriage was a sacrament which the Church controlled. Though there were plenty of aristocrats in the post-Roman West, the political systems of control were relatively weak. The Western Church was a solid and critical institution which spanned the patchwork of independent dominions which characterized the political landscape. It was indispensable.
In a world where Rome did not fall, which to all practical purposes was the case in the East, the Church would have had a more normal role in society. It would not have been able to engage in a social engineering project, because established powers would have blunted its will. This is clearly the case in other societies. In addition, the Church also had accrued to itself a monopoly on provision of religious services in Late Antiquity, and so it had recourse to avenues of leverage not feasible for secular rulers.
The pervasive power of the Western Church even in the face of the rise of social and political complexity in the late medieval period is illustrated by the impact of the Reformation. In Protestant areas of Europe religion became much more strictly subordinated to the ruler. Pastors became more like civil servants than independent sources of power. Two dynamics emerged rapidly with the adoption of Protestantism. First, the cousin marriage became more common among elite lineages again (e.g., Charles Darwin married his cousin). Second, young women were forced into marriages against their will more often than in Catholic Europe, where becoming a nun was often an option. To some extent Protestantism exacerbated the tendency to treat and see women bargaining chips in negotiations between elite lineages.
As the authors note in the preprint inbred lineage groups to come to the fore and operate as the atomic units of social organization in a society among agriculturalists. This is in contrast to hunter-gatherers, who seem to want to create kinship ties to distant people. There are clear differences between foragers and farmers in this model. Dense sedentary living fosters the emergence of endogamous kinship groups as natural cultural adaptations. The peculiarity about Western Europe is that this society broke out of this “default state,” and even after the Protestant Reformation it never went back. It may be that European society is now at a different equilibrium, or, that the economic lift-off of the last 500 years has allowed for individualism to persist even where the role of the Church in breaking up tight kinship groups has been blocked.
This preprint is a big deal, because it brings quantitative methods to a field which has been long on speculation. But there’s a real phenomenon that needs to be explored.
Addendum: The blogger “hbd chick” has suggested that she should have been cited, as she has been talking about these issues relating to family structure and the Church for many years. I am not taking any sides, but just pointing that out.
A few days ago a minor controversy about the cultural context of human sacrifice in Mesoamerica cropped up. A writer at Science, wrote a piece, Feeding the gods: Hundreds of skulls reveal massive scale of human sacrifice in Aztec capital. The article was good. But it elicited some emotional responses from readers. As one sees in the earliest writings of the Spanish, the Aztec penchant for human sacrifice often results in a moralistic reaction.
The writer of the piece took to Twitter to disagree with the moralistic tone of many who read her article. It being Twitter, her original series of comments were easy to misinterpret or exaggerate, and she had to post a follow-up clarifying some issues. Below is a response to one of her original assertions.
Basically, I agree that our feelings about sacrifice today are irrelevant to understanding it. To understand human history and something scientific that relates to humans it is important to set aside feelings, at least for the moment. That being said, let me remind the reader that this is not the attitude of many science writers when a story has a “social justice” angle. We all know if a science article has a social hook which appeals to emotional or moralistic impulses in the readership, it will probably be injected into it for purposes of clicks and adding an extra layer of meaning and relevance. For various reasons, Aztec human sacrifice is better presented in a dispassionate manner, as Mesoamerican human sacrifice doesn’t lend itself easily to a standard social justice narrative (i.e., the “villains” are not white).
The Aztec Empire, or the Triple Alliance if you prefer, was built on brutality. From what we can tell it was an analog in the New World to what the Assyrian Empire had been in Eurasian antiquity: apolity bound together through brutal coercion.
Here is one tale from Aztec history that is well known:
In 1323, they asked the new ruler of Culhuacan, Achicometl, for his daughter, in order to make her the goddess Yaocihuatl. Unknown to the king, the Mexica actually planned to sacrifice her. The Mexica believed that by doing this the princess would join the gods as a deity. As the story goes, during a festival dinner, a priest came out wearing her flayed skin as part of the ritual. Upon seeing this, the king and the people of Culhuacan were horrified and expelled the Mexica.
Note that the legend is recounted whereby the other native peoples of Mexico were horrified by the Aztec behavior. This highlights the reality that human sacrifice seems to elicit negative reactions generally. It’s not arbitrary. In Carthage Must Be Destroyed the author spends a great deal of time exploring the reality of child sacrifice in that society. A practice in decline in the Phoenician homeland, for some reason it reemerged in the western Mediterranean much more vigorously. Classical observers found the practice grotesque, and their descriptions of Carthaginian child sacrifice were suspected by many scholars as being scurrilous. Fortunately, or unfortunately, the truth has been established by the discovery of bones of children in urns. The key point to note is that ancient observers were just as judgemental as modern people.
Though human sacrifice persisted in some form in many antique societies, it is clear that what was once a common occurrence in the Bronze Age world became rarer with time, until it was no longer socially or ethically acceptable. Researchers in the field of cultural evolution have explored the emergence and decline of human sacrifice. Though there are no current definitive conclusions, it seems likely that it crops up in societies which have transitioned toward being highly inegalitarian. But, it declines again in societies which scale large enough to the point where more abstract ideological and political systems must bind groups of people together. The Classical Western world, India, and China, all seem to be marked by a recollection of normative human sacrifice (e.g., Iphigenia), and a turn away from it.
The inequality aspect is important. Though some people willingly gave themselves as human sacrifices, there are recurrent themes of low-status individuals within the group (e.g., slaves) or outsiders (prisoners of war) being given to the gods. There is debate as to the nature of the Aztec “flower wars”, but one traditional explanation is that they were driven by the need for victims of human sacrifices.
In other words, Aztec human sacrifice can be contextualized in a generalized framework. But that is not where the writer of the original piece went on the Twitter thread. Rather, she seems to have bracketed the practice by modern social and political considerations, “centuries of colonial oppression and destruction.” To be frank, it is a strongly Eurocentric narrative where everything before European colonialism is viewed as a prologue to the true story. The only story that matters. The context of Aztec human sacrifice that matters to many people steeped in this way of thinking is what the Spaniards did to the native peoples of the New World after the conquest of the Aztec Empire. Like ethical tachyons the present blasts back into the past, and reshapes our whole perception of it in current terms. The Aztec tendencies toward brutality, oppression and grotesque customs such as human sacrifice, are inconvenient to this framework.
The cultural conditioning isn’t that of a Western individual who lives in a consumer society at the tail end of a two-century path of growth, domination, and maturation. Rather, the cultural conditioning is of a whole class of intellectuals steeped in understanding all social and historical relations as but mirrors of the one which defined the 19th and 20th century. This viewpoint also asserts that this period, these people, are sui generis. It is profoundly Eurocentric to the bones.
To me when considering the ethical and historical frame of human sacrifice two facts jump out to me. First, it’s an empirical fact that at certain levels of social complexity human sacrifice seems to emerge, and at later levels of social complexity tends to be dampened and abolished. The reason that it tends to be dampened and abolished is probably the reason that the Spanish found it easy to obtain native allies against the Aztec Empire: human sacrifice is a costly and brutal way to foster social cohesion. Across societies, there has been a general tendency to abandon the practice and create psychologically satisfying substitutes which don’t have the bloody downsides.
The second aspect is more primal: humans don’t like to die. It is true that humans will sacrifice themselves, or in the case of Carthaginian nobles, their own children, in exigent circumstances. Human nature exists, and many aspects are universal. The abhorrence of human sacrifice doesn’t emerge out of particular and unique elements of Western colonial culture, it has cropped up in many societies, and I would suggest that the shoe is on the other foot here: those who argue for human sacrifice have to make the argument for it is necessary. And that is why so often humans who are sacrificed are those who can least choose to give their own lives. Slaves, children, prisoners, and criminals.
Unfortunately, the Western colonial narrative looms so large for many moderns that other cultures and other histories are erased in all their complexity. They gain depth and richness only as handmaids to the deconstruction and critique of the Western colonial narrative.
For some reason women do not seem to migrate much into South Asia. In the late 2000s I, along with others, noticed a strange discrepancy in the Y and mtDNA lineages which trace one’s direct male and female lines: in South Asia the male lineages were likely to cluster with populations to the north an west, while the females lines did not. South Asia’s females lines in fact had a closer relationship to the mtDNA lineages of Southeast and East Asia, albeit distantly.
One solution which presented itself was to contend there was no paradox at all. That the Y chromosomal lineages found in South Asia were basal to those to the west and north. In particular, there were some papers suggesting that perhaps R1a1a originated in South Asia at the end of the last Pleistocene. Whole genome sequencing of Y chromosomes does not bear this out though. R1a1a went through rapid expansion recently, and ancient DNA has found it in Russia first. But in 2009 David Reich came out with Reconstructing Indian population history, which offered up somewhat of a possible solution.
What Reich and his coworkers found that South Asia seems to be characterized by the mixture of two very different types of populations. One set, ANI (Ancestral North Indian), are basically another western or northwestern Eurasian group. ASI (Ancestral South Indian), are indigenous, and exhibit distant affinities to the Andaman Islanders. The India-specific mtDNA then were from ASI, while the Y chromosomes with affinities to people to the north and west were from ANI. In other words, the ANI mixture into South Asia was probably through a mass migration of males.
But it’s not just Y and mtDNA in this case only. A minority of South Asians speak Austro-Asiatic languages. The most interesting of these populations are the Munda, who tend to occupy uplands in east-central India. Older books on India history often suggest that the Munda are the earliest aboriginals of the subcontinent, but that has to confront the fact that most Austro-Asiatic language are spoken in Southeast Asia. There was no true consensus where they were present first.
Genetics seems to have solved this question. The evidence is building up that Austro-Asiatic languages arrived with rice farmers from Southeast Asia. Though most of the ancestry of the Munda is of ANI-ASI mix, a small fraction is clearly East Asian. And interestingly, though they carry no East Asian mtDNA, they do carry East Asian Y. Again, gene flow mediated by males.
Zoroastrianism is one of the oldest extant religions in the world, originating in Persia (present-day Iran) during the second millennium BCE. Historical records indicate that migrants from Persia brought Zoroastrianism to India, but there is debate over the timing of these migrations. Here we present novel genome-wide autosomal, Y-chromosome and mitochondrial data from Iranian and Indian Zoroastrians and neighbouring modern-day Indian and Iranian populations to conduct the first genome-wide genetic analysis in these groups. Using powerful haplotype-based techniques, we show that Zoroastrians in Iran and India show increased genetic homogeneity relative to other sampled groups in their respective countries, consistent with their current practices of endogamy. Despite this, we show that Indian Zoroastrians (Parsis) intermixed with local groups sometime after their arrival in India, dating this mixture to 690-1390 CE and providing strong evidence that the migrating group was largely comprised of Zoroastrian males. By exploiting the rich information in DNA from ancient human remains, we also highlight admixture in the ancestors of Iranian Zoroastrians dated to 570 BCE-746 CE, older than admixture seen in any other sampled Iranian group, consistent with a long-standing isolation of Zoroastrians from outside groups. Finally, we report genomic regions showing signatures of positive selection in present-day Zoroastrians that might correlate to the prevalence of particular diseases amongst these communities.
The paper uses lots of fancy ChromoPainter methodologies which look at the distributions of haplotypes across populations. But some of the primary results are obvious using much simpler methods.
1) About 2/3 of the ancestry of Indian Parsis derives from an Iranian population 2) About 1/3 of the ancestry of Indian Parsis derives from an Indian popuation 3) Almost all the Y chromosomes of Indian Parsis can be accounted for by Iranian ancestry 4) Almost all the mtDNA haplogroups of Indian Parsis can be accounted for by Indian ancestry 5) Iranian Zoroastrians are mostly endogamous 6) Genetic isolation has resulted in drift and selection on Zoroastrians
The fact that the ancestry proportion is clearly more than 50% Iranian for Parsis indicates that there was more than one generation of males who migrated. They did not contribute mtDNA, but they did contribute genome-wide to Iranian ancestry. There are wide intervals on the dating of this admixture event, but they are consonant oral history that was later written down by the Parsis.
So there you have it. Another example of a population formed from admixture because women hate going to India.
Citation: The genetic legacy of Zoroastrianism in Iran and India: Insights into population structure, gene flow and selection. Saioa Lopez, Mark G Thomas, Lucy van Dorp, Naser Ansari-Pour, Sarah Stewart, Abigail L Jones, Erik Jelinek, Lounes Chikhi, Tudor Parfitt, Neil Bradman, Michael E Weale, Garrett Hellenthal bioRxiv 128272; doi: https://doi.org/10.1101/128272
In 2012 I wrote Post-Neolithic revenge of the foragers. There were two proximate rationales for my thoughts at the time. First, I thought Peter Bellwood’s thesis of agricultural based demographic expansions in First Farmers was being vindicated in the broadest sketch, but there were many countervailing details. Second, there were already suggestions that genetic data was not indicative of a final victory of farmers by pastoralists.
There were several immediate issues that came to mind in the non-genetic domain. Bellwood argued that agriculture shape the distribution of modern language families, but the spread of Turkic and Finnic peoples seem likely to have been post-agricultural, and not based on farming. Both these groups were arguably nomadic, one pastoralist, and the other engaging in mixed use lifestyles which were reminiscent of classic hunting and gathering. And, there has been anthropological evidence that though pure hunter-gatherers, such as indigenous Australians, do not take to cultivation easily, they quickly transition to pastoralism. In other words, the skills and mores which are common among hunter-gatherers can translate rapidly once domesticate based nomadism spreads.
The Turks, or the Saami with their reindeer, are evidence of this transition, and its success. It seems plausible that the same was the case with Indo-Europeans, and that is what I thought at the time.
Now we have more data from ancient DNA. It does seem there was a “resurgence” of Mesolithic hunter-gatherer ancestry as time passed, with Neolithic farmers exhibiting a more indigenous genetic profile in Europe. Additionally, the arrival of Indo-European steppe ancestry brought another dollop of “hunter-gatherer” ancestry from beyond the fringes of Europe proper.
So what story can we tell of the transition between the Late Neolithic (LN) and the Early Bronze Age (ENA) in Europe? First, the proto-Indo-Europeans were people from the fringes and boundaries. Their genetics indicate some sort of influence from the Near East, likely via the Maykop people. But their roots were also deep in eastern Europe, from the local hunter-gatherers who had affinities with Siberians to their east and European hunter-gatherers to their west. From from this synthesis emerged something special, a warlike group of mobile pastoralists who quickly swept the field.
This reminds me of something from Peter Turchin’s book, War and Peace and War: The Rise and Fall of Empires. Populations on the borders or frontiers of ethno-cultural (and possibly political) zones may exhibit more group cohesion than those from “core” areas. The Indo-Europeans were a border folk. They may also take to cultural innovations more quickly, in The Making of a Christian Aristocracy it is clear that switching to the new religion occurred faster among elites in outlying regions than in the core.
A second issue, which is not proven, but may be possible, is that once the Indo-Europeans moved into the North European plain, they allied with residual hunter-gatherer populations. A classic enemy-is-my-enemy proposition. This would likely result in a higher proportions of Pleistocene ancestry in later generations due to assimilation.
The moral of the story is that often there is no final victory in the war. Human history is full of reversals.
Virpi Lummaa’s group has another paper, Offspring fertility and grandchild survival enhanced by maternal grandmothers in a pre-industrial human society:
