Genetic study Hunter-gatherer genetic persistence at the onset of megalithism in Western Iberia

Tautalus

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Y-DNA haplogroup
I2-M223 / I-FTB15368
mtDNA haplogroup
H6a1b2
Abstract

Despite its strategic importance at the furthermost edge of the Neolithic expansion in Europe, archaeogenetic data from Mesolithic and Neolithic human remains from Portugal are still very limited. Here we present ancient mtDNA evidence (mostly unpublished) to fill the gap and discuss the pattern of “genetic resurgence” of hunter-gatherer (Mesolithic) ancestry, widely reported elsewhere in Europe, among the first megalith builders (Middle Neolithic) of western Iberia.

A total of 11 Mesolithic and Neolithic necropolises located in the central and southern regions of Portugal dated to ca. 6200–3000 BC were studied. These sites comprise all Mesolithic–Neolithic cultural stages and include several funerary architectures and spaces. Reproducible mtDNA HVRI haplotypes were obtained from 23 individuals from six different archaeological sites spread across a >3000-year transect, from the Late Mesolithic to the Late Neolithic.

Our results support a three-stage explanatory demographic and populational model: i) local hunter-gatherer populations constituted a highly homogeneous genetic pool; ii) the first farming practices were introduced by human groups carrying new, extraneous haplogroups and exhibiting the signature of admixture events occurring at the time of first contact with local hunter-gatherers; iii) the genetic pattern detected among the megalith-building populations, showing hunter-gatherer along with farming ancestry, may be explained by the segmentary principles, and attendant endogamic practices, that structured Neolithic societies.

Percentage of mtDNA and Y chromosome haplogroups of pre-Neolithic (local), Neolithic (imported from the Near East) and unknown/other origin.
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The conclusions of the article show a relative genealogical continuity across changes in lifestyle and technology in the region.

Some excerpts :

"When our Early and Middle Neolithic Portuguese mtDNA results are combined with previously published data for these time periods in Iberia, an increase in the frequency (ca. 30%) of maternal hunter-gatherer lineages in the transition from the Early to the Middle Neolithic (ca. 3900 BC), peaking at ca. 3900–3500 BC, can be observed. This interval coincides with the consensus chronology for the onset of megalithism along western Iberian regions (Schulz-Paulsson, 2019). In contrast, pre-Neolithic Y chromosome lineages, I2a in particular, seem to be prevalent in Iberia through the whole of the Neolithic, with an average frequency of 40–60% according to published data (Fig. 2 and Table 3). This persistence of hunter-gatherer ancestry inferred from uniparental markers is also evident in whole genome analyses, with Middle Neolithic populations from Iberia and elsewhere in Europe falling in a cline of admixture between ANF and WHG"

"Local Mesolithic hunter-gatherers show a remarkable mtDNA homogeneity, in which U5-derived mitochondrial haplogroups are exclusive. This is found in the two main core areas of Mesolithic settlement in the country—Muge and Sado (Fig. 1A)—and further confirms similar conclusions previously reached elsewhere in Iberia. This is in good accord with the long-acknowledged cultural homogeneity that globally characterizes the peninsula's last hunter-gatherer communities."

"The arrival of farming lifeways to western Iberia is due to a migration process that eventually triggers the neolithization of the entire region. The earliest well-documented entry point of new human populations is the middle and upper sectors of Portuguese Estremadura (Fig. 1A), resulting in the presence of HV, J2, T2, N and H mitochondrial haplogroups at Caldeirão, Picoto, and Galeria da Cisterna (this study; Olalde et al., 2015; Allentoft et al., 2022). Two of the Caldeirão individuals show 27−43% of local Iberian WHG ancestry. The limited number of analysed Cardial samples does not allow a finer characterisation of the exact location and time of admixture, though local admixture of the immediate ancestors of this group seems highly likely given that the Caldeirão individuals (the earliest of which is dated to 5477–5364 BC, 2σ calibrated interval; see Zilhão, 2021) are among the country's first farmers."

"Unlike seen among Early Neolithic individuals, no evidence for exogenous genetic inputs is observed around 3500–4000 BC, among the earliest megalith builders. A significant percentage of typically WHG haplogroups is visible in the number of analysed individuals from Barrão and Bom Santo belonging to U5-derived mitochondrial haplogroups (known in Early Neolithic Spain but so far undetected in coeval individuals from Portugal) (Table 3). Though these data were obtained from cave sites in the limestone massifs of Estremadura, not from dolmens (due to taphonomic limitations derived from the latter's location in acidic soils), current archaeological evidence supports that we are dealing with the same populational pool. Explanations for this pattern—which, in western Iberia, would seem to be better described as one of persistence rather than resurgence—can tentatively be sought on these communities' social organisation, of segmentary type, along with population growth"
 
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the temporal trend is a bit 'cahotic'; but as a whole I see a big difference between the males and females input. I don't know what explain this numeric domination of HG's males over Neolithic males?
 
Even though the circumstances of this persistence and dominance of local hunter-gatherer paternal lineages over those of farmers are unknown, the most plausible hypothesis is that hunter-gatherers violently took control of existing agricultural societies and that this event occurred simultaneously in various locations in Europe.
We will never know the dynamics in place, but maybe it’s another episode of the Nomad-Sedentary dichotomy, the constant conflict and shifts of power that existed between the two types of society throughout history.
It also raises some interesting questions, like do the beliefs, the culture, the language of megalithic societies originate from the hunter-gatherers, the farmers, a mixture of both?
We probably never know.​
 
Even though the circumstances of this persistence and dominance of local hunter-gatherer paternal lineages over those of farmers are unknown, the most plausible hypothesis is that hunter-gatherers violently took control of existing agricultural societies and that this event occurred simultaneously in various locations in Europe.
We will never know the dynamics in place, but maybe it’s another episode of the Nomad-Sedentary dichotomy, the constant conflict and shifts of power that existed between the two types of society throughout history.
It also raises some interesting questions, like do the beliefs, the culture, the language of megalithic societies originate from the hunter-gatherers, the farmers, a mixture of both?
We probably never know.​
Rather agree with your supposition.
 

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