Kinship practices in the early state El Argar society from Bronze Age Iberia

1 Vol.:(0123456789) Scientific Reports | (2022) 12:22415 | https://doi.org/10.1038/s41598-022-25975-9 www.nature.com/scientificreports Kinship practices in the early state El Argar society from Bronze Age Iberia Vanessa Villalba‑Mouco 1,2*, Camila Oliart 3, Cristina Rihuete‑Herrada 3, Adam B. Rohrlach 1,4, María Inés Fregeiro 5, Ainash Childebayeva 1, Harald Ringbauer 1, Iñigo Olalde 6,7,8, Eva Celdrán Beltrán 3, Catherine Puello‑Mora 3, Miguel Valério 3, Johannes Krause 1, Vicente Lull 3, Rafael Micó 3,9*, Roberto Risch 3,9* & Wolfgang Haak 1,9* The Early Bronze Age in Europe is characterized by social and genetic transformations, starting in the early 3rd millennium BCE. New settlement and funerary structures, artifacts and techniques indicate times of change with increasing economic asymmetries and political hierarchization. Technological advances in metallurgy also played an important role, facilitating trade and exchange networks, which became tangible in higher levels of mobility and connectedness. Archeogenetic studies have revealed a substantial transformation of the genetic ancestry around this time, ultimately linked to the expansion of steppe‑ and forest steppe pastoralists from Eastern Europe. Evidence for emerging infectious diseases such as Yersinia pestis adds further complexity to these tumultuous and transformative times. The El Argar complex in southern Iberia marks the genetic turnover in southwestern Europe ~ 2200 BCE that accompanies profound changes in the socio‑economic structure of the region. To answer the question of who was buried in the emblematic double burials of the El Argar site La Almoloya, we integrated results from biological relatedness analyses and archaeological funerary contexts and refined radiocarbon‑based chronologies from 68 individuals. We find that the El Argar society was virilocally and patrilineally organized and practiced reciprocal female exogamy, supported by pedigrees that extend up to five generations along the paternal line. Synchronously dated adult males and females from double tombs were found to be unrelated mating partners, whereby the incoming females reflect socio‑political alliances among El Argar groups. In three cases these unions had common offspring, while paternal half‑siblings also indicate serial monogamy or polygyny. The beginning of the European Bronze Age (BA) involved drastic social changes that resulted in strong political centralization, growing economic inequality, and settlement and demographic disruptions. These social changes are striking in particular regions, such as Central Europe, Brittany, southern England and southeastern Iberia, where the unequal distribution of wealth, as reflected in the grave goods, becomes more apparent and consistent1–3. Recent genomic analyses have suggested that these changes were related to the westward expansion of "stepperelated ancestry" and the reduction in diversity of male lineages in most of Europe, following a process that began in the early 3rd millennium cal BCE in Eastern Europe4–8. In this context, increased violence and social coercion could have played a role in new social relations (e.g.,9–12). However, the role and nature of population movements (violent or peaceful), or expansions in this process remain a matter of debate. Following the introduction of game-shifting innovations13, other factors, such as new economies, climate change or infectious diseases14–17 OPEN 1Department of Archaeogenetics, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany. 2Instituto Universitario de Investigación en Ciencias Ambientales de Aragón, IUCA-Aragosaurus, Zaragoza, Spain. 3Department of Prehistory, Universitat Autònoma de Barcelona, Barcelona, Spain. 4School of Mathematical Sciences, University of Adelaide, Adelaide 5005, Australia. 5Independent researcher, Murcia, Spain. 6BIOMICs Research Group, Department of Zoology and Animal Cell Biology, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain. 7Ikerbasque-Basque Foundation of Science, Bilbao, Spain. 8Department of Genetics, Harvard Medical School, Boston, MA, USA. 9These authors contributed equally: Rafael Micó, Roberto Risch and Wolfgang Haak. *email: [email protected]; [email protected]; R[email protected]; [email protected] 2 Vol:.(1234567890) Scientific Reports | (2022) 12:22415 | https://doi.org/10.1038/s41598-022-25975-9 www.nature.com/scientificreports/ might also account for socio-economic and genetic changes detected throughout the transformative times of the 3rd millennium BCE in Europe. In addition, the magnitude of transformations varied in each region. More integrative work is needed to understand the relative contribution of different factors in such intricate processes of change at local and cross-regional levels. The archeological complex of El Argar in southeastern Iberia provides a key case study for deepening our knowledge of social-political reorganization in the European Early BA (EBA) (Fig.1A). El Argar is one of the archeological entities in which a socio-economic divide18,19 and a genetic shift are clearly documented8, and it is arguably one of the first highly complex societies in Western Europe to reach the status of an early state1,19–21. El Argar developed over three phases from ca. 2200 to 1550cal BCE19, spreading from its heartland in the coastal lowlands into the inner highlands, and covering ~ 35,000 km2 at its peak. The Argaric archeological record includes permanent and densely populated hilltop settlements of up to 5 hectares in size. These settlements were organized and managed hierarchically, with evidence of public buildings for political decision-making22, and structures for water supply. Moreover, large-scale storage and processing of cereal crops23, specialized pottery Figure1. Early bronze age El Argar in southern Iberia. (A) Map of Iberia and location of the Argaric and other Bronze Age nearbysites. The map was created using QGIS 3.12 (https:// qgis. org/ en/ site/) and uses Natural Earth vector map data from (https:// www. natur alear thdata. com/ downl oads/). (B) A view of the La Almoloya hilltop site from the East. 3 Vol.:(0123456789) Scientific Reports | (2022) 12:22415 | https://doi.org/10.1038/s41598-022-25975-9 www.nature.com/scientificreports/ and metallurgical production, and intensive subsistence systems combining rainfed agriculture, manuring and small-scale irrigation are found at Argaric sites18,19,24. Argaric sites offer a unique opportunity to address questions of biological relatedness and kinship, since a substantial proportion of the population was buried in single or double tombs, placed under the settled areas. These funerary practices allow us to link individuals, grave goods, tombs, and architectural units diachronically, which is rare in late prehistoric Europe. To date, Argaric archeology has approached questions of kinship through the analysis of double tombs, which represent nearly 20% of burials in certain sites. On average, more than half of these tombs were assigned to two adults, a quarter were occupied by an adult and a child, and the combination of two children was far less common (~ 10%)25. The main focus of previous research has been on double tombs with two adults, usually a male and a female, providing the basis for the hegemonic model since the late nineteenth century: specifically, that these graves were thought to reflect heterosexual, monogamous couples (‘marriages’) as the basis for nuclear families26–29. To test this ‘marriage’ hypothesis, male and female skeletons in double tombs were sampled for radiocarbon dating in the late 1980s. A statistical analysis of paired 14C dates from a sample of 23 double burials suggested a cross-generational gap for most pairs of individuals30, which led to the alternative hypothesis that the relationships between adults in double tombs were genealogical rather than socio-political. As a result, descent/consanguinity, matrilocality and matrilineality were proposed as the main principles of Argaric kinship practices25,31–33. The aim of this study is to use state-of-the-art ancient DNA methods to determine the nature of the genetic relationships between individuals from El Argar contexts, and to use these as new evidence to shed light on kinship practices and social organization of the Argaric society, including inheritance rules that are potentially linked to households. Moreover, we aim to investigate the prevailing hypotheses on Argaric kinship practices, through an interdisciplinary approach that combines genetic, osteological, and fine-grained contextual information from archeological excavations. The bulk of our data comes from the site of La Almoloya in Murcia22,34, which, due to its unique preservation and extensive excavations, features a variety of burial types and grave goods, complemented by detailed anthropological data and a radiocarbon and stratigraphy-based chronology (Supplementary 1, Fig.1B). The results are expected to improve our understanding of one of the earliest, highly complex societies in BA Europe. Data overview and detection of genetic relationships At La Almoloya we sampled 86 individuals with suitable morphological preservation from a total of 101 graves, containing the remains of 128 individuals (Dataset S1.1). We obtained high-quality genome-wide data (1240k SNP capture data) for 68 individuals (79% success rate) passing our quality control thresholds (< 4% contamination, characteristic aDNA damage profiles, unambiguous sex determination) (“Materials and methods”, Dataset S1.2). The 68 individuals from La Almoloya cover El Argar phase 2 (n = 41) and phase 3 (n = 27) of the local stratigraphy (2000–1750cal BCE and 1750–1550cal BCE, respectively), and we observed no bias with respect to post-depositional or taphonomic factors (“Materials and methods”). The relative frequencies of females and males, adults and subadults with genetic results match those of the physical anthropological examination for each of these demographic groups, indicating that the sample is representative of the group buried at the site (Dataset S1.3). Another three individuals from La Almoloya yielded autosomal SNP data below the threshold of 20,000 SNPs: ALM037 (18,226 SNPs), ALM045 (10,970 SNPs), ALM033 (356 SNPs) with no contamination estimate (Dataset S1.2). These three individuals were only included in some analyses to confirm or exclude potential 1st-degree biological relationships, which is also possible for low coverage data (Supplementary 2). To estimate the biological relatedness among La Almoloya individuals and also among and between other published BA individuals from Iberia, we first calculated the pairwise mismatch rate (PMR) (Supplementary 2, Fig.S1), which also provides a general threshold of background (un-)relatedness in BA Iberia from randomly drawn pairs of individuals6,7,35. Here, individuals from neighboring El Argar and Iberian BA groups were of particular interest for the comparison and discussion of results (Dataset S1.28). In total, we report 13 1st-degree-relationships and 10 2nd-degree-relationships among the 68 individuals at La Almoloya, involving 34 individuals (50%) for which genome-wide data was generated (Fig.2, Supplementary 2; Fig.S1–S4, Dataset S1.4-S1.6). Of note, 1st-degree relatives can be parent–offspring or full siblings, and 2nd-degree relationships include aunt-uncle/niece-nephew, grandparent-grandchild, and half-siblings (who share only one of the biological parents). We were able to reconstruct seven pedigrees involving all 1st-degree relationships and to extend some of these pedigrees up to five generations (Fig.3, Supplementary 3, Fig.S5). In addition, we found pairs that were 2nd-degree relatives. We set these aside as ‘unresolved pedigrees’ due to the lack of bridging 1st-degree relatives and the fact that we were unable to unambiguously determine the exact genealogical relationships despite the integration of osteological and archeological data (Supplementary 3, Dataset S1.4–S1.6). With the help of an Identity-by-descent (IBD) analysis of imputed high-quality genome-wide data from selected pairs (> 600,000 SNPs; “Materials and methods”), we also found evidence for more distant genetic relationships up to the 6–7th degree between individuals from three of the seven reconstructed pedigrees, as well as more distant connections between sites (Supplementary 2, Fig.S4, Dataset S1.7). Reconstructed pedigrees from nearby BA sites are shown in Supplementary 4. We notice a similar frequency of 1st-(N = 13) and 2nd-degree (N = 10) related individuals. As the number of 2nd-degree relatives is expected to double that of the 1st-degree relatives, the burials at La Almoloya seem to emphasize the closest biological ties if we disregard the number of unrelated individuals also buried there. While the number of samples is too small to provide robust statistical support, the underrepresentation of 2nddegree relatives indicates that not all biological relatives were buried in the settlement, which suggests inter-site mobility, involving residential changes for a substantial part of the population. A concomitant increase in child 4 Vol:.(1234567890) Scientific Reports | (2022) 12:22415 | https://doi.org/10.1038/s41598-022-25975-9 www.nature.com/scientificreports/ burials during phase 3 (a common feature during late Argaric times 30), suggests an emphasis in funerary rites on the closest biological offspring, or an increase in child mortality. In what follows, we describe the results of the estimation of biological relatedness in reference to the physical distances between the burials, starting with closely inhumated individuals in double burials followed by relatives separated by larger distances at the site. Double burials of two adults. Double burials are an iconic feature of the El Argar group and play a central role in the discussion of Argaric kinship. This type of burial had already been attested to in earlier times at southeast Iberian sites such as Molinos de Papel36,37, and continued to be practiced during phases 2 and 3 of El Argar. At La Almoloya, 48 out of 126 individuals (38%) were buried in 24 double tombs. The majority of these tombs (N = 20) contained two adults (fourteen from phase 2 and six from phase 3), while the rest were either two Figure2. (A) Plan of La Almoloya phase 3 highlighting the position of burials that have yielded sufficient aDNA and close genetic relatedness between individuals up to the 2nd degree. For full pedigrees see SI Appendix, Sect.3. (B) Exemplary pithos double burial and grave goods (C) from La Almoloya burial AY38. 5 Vol.:(0123456789) Scientific Reports | (2022) 12:22415 | https://doi.org/10.1038/s41598-022-25975-9 www.nature.com/scientificreports/ Figure3. Summary of the genetic results from the double burials at Almoloya. (A) Results of the Pairwisemismatch rate (PMR) analysis including all pairs of individuals from the Iberian Bronze Age available to date. The x-axis shows the number of overlapping SNPs between each pair and the y-axis the coefficient of relatedness. All adult double burials fall within the range of randomly drawn pairs of individuals from the Iberian Bronze Age. (B) Reconstructed pedigrees of three cases involving adult double burials and their common offspring. Below the colored squares and circles is the contextual information of all adult double tombs, including sex, age at death, mitochondrial and Y-chromosomal haplogroups, direct 14C dates, as well as stratigraphy. Pink outlines reflect interchangeable genetic sexes and gray dashed lines indicate pedigrees reconstructed from low coverage data. 6 Vol:.(1234567890) Scientific Reports | (2022) 12:22415 | https://doi.org/10.1038/s41598-022-25975-9 www.nature.com/scientificreports/ children or one adult and one child. In one of the adult double burials (AY80), the remains of a skull of a third individual were placed under a slab outside the cist, after the tomb had already been sealed. We successfully retrieved genomic data from both skeletons for ten adult double burials (20 individuals). The genetic results confirmed the anthropological morphological sex determination of the individuals, and in all ten cases the double burials contained a male and a female, which were found to be genetically unrelated, with the coefficient of relatedness between them being 0.001 (ranging from − 0.024 to 0.022) (Fig.3A, Dataset S1.4, Supplementary 2). Each pair of double burial adults yielded PMR values which were close to the baseline median of the PMR values, which was established from all unrelated pairs of Iberian BA individuals across many sites. Significant overlap of the calibrated ranges from direct radiocarbon dates of all analyzed pairs makes the coexistence of both individuals possible (Fig.2, Supplementary 5, Fig S6, Dataset S1.2, Dataset S1.8). All analyzed adult couples carried different mitochondrial haplogroups, which ruled out direct maternal links (Dataset S1.2). This observation can also be extended to other Argaric sites, such as Cerro del Morrón, from where we also analyzed a contemporaneous, adult double burial that contained an unrelated female (CMO001) and male (CMO002), and other BA sites from southeastern Iberian BA, such as Molinos de Papel (MPD002, female and MPD003, male) (Supplementary 2, Dataset S1.2). In another adult double burial (AY82) we obtained good coverage data for the female individual (ALM018), but not for the male (ALM045), however the results of the biological relatedness tests still suggested that the pair was not related (Fig.3A, Dataset S1.4). In addition, in three out of ten cases from La Almoloya, males and females from double burials had offspring together, and thus represented mates (Fig.3B). This observation suggests the existence of female–male socio-political alliances in life, which were also symbolized in the funerary practices of the El Argar society. So far, the contemporaneous intra-site genomic studies have reported the presence of sexual partners at the site confirmed by common offspring but buried in different graves 38. In other examples, only one of the biological parents was found buried at the site 39–41. An outstanding example is the high-status pithos double burial AY38 from the palatial building (Fig.2B), in which a man (ALM039) and a woman (ALM038) were endowed with rich grave goods (Fig.2C) and thus were interpreted as having been prominent members of the ruling class22. The woman was buried with one of the five silver diadems found uniquely at Argaric sites (the other four are from the eponymous El Argar site, about 100km south of La Almoloya). This outstanding funerary item has been interpreted as a symbol of distinction and power of some El Argar women22. From the funerary context we know that the man died first, just shortly before the woman, because his skeleton was found beneath her featuring a remarkably low degree of disarticulation and joint displacement, in particular along the spine and the thorax. We found a common daughter in the double grave AY30 (ALM030) buried in a pit without goods in a different architectural complex, further away from her parents (Fig.3B). ALM030 had passed away prematurely at an estimated age of 14–17months. Another outstanding example of a double burial containing partners is AY80. The stone cist contained a 30–35-year-old female (ALM015) and a 35–40-year-old male (ALM016) attributed to the high social class (Fig.3B). The funerary context suggests that the woman had died first and her bones were then collected and deposited in a bundle on top of the male burial, which took place at a later time. Both had a common son (ALM052), who reached 45–50years of age and was buried without grave goods 11m away, together with the adult female ALM053, who was buried after him, both in another adult double burial AY42. The skull of an adult male (ALM017) from outside the cist in which the couple from AY80 had been buried, was found to be related in the 3rd degree to both individuals in AY80. Additional IBD analysis of the pair ALM015 and ALM017 confirmed the 3rd-degree relationship in direct generational succession, who together with ALM016 thus represent great-grandparents and great-grandson (Fig.3B; Supplementary 2, Dataset S1.7). In addition, we found that the great-grandson, ALM017, was 1st-degree related to ALM060, his 18–20-monthold daughter who was buried in a pithos in the same area. This constitutes the largest pedigree reconstructed in La Almoloya, which connects relatives over five generations spanning phases 2 and 3, from the great-greatgrandparents (ALM015 and ALM016) to the great-great-granddaughter (ALM060), in a relatively close area, even though generations are missing, remained untyped, or might have been buried elsewhere (Fig.3B, Supplementary 2, Fig.S4). While the small number of cases and limitations of 14C date ranges do not allow the generalized assumption of genealogical links across phases, this example argues against the possibility that the dramatic changes in settlement layout in phase 3 were undertaken by an entirely new group or dynasty. Genetic continuity at the population level between the two phases, as described in8, also rules out scenarios of drastic demographic changes (Supplementary 5, Fig.S7). Grave AY22 represents another adult double burial with common offspring (Fig.3B). The burial contained a 35–45-year-old female (ALM048) and an adult male (ALM049), whose state of preservation did not permit a more precise age estimation. We identified their common adult son ALM034 in a single cist burial (AY16) less than 3m away from AY22. Taken together, males and females from adult double tombs were not found to be genetically related to each other. Irrespective of this finding, these individuals were involved in all 1stand 2nd-degree relationships among adults at the site, which suggests that double burials displayed a central social role (Fig.3B, Supplementary 2, Supplementary 3). Double burials with an adult and a child. At La Almoloya, we documented three double burials containing an adult and a subadult individual, of which only one could be analyzed genetically. Cist burial AY21 contained a 30–35-year-old woman (ALM073), who was buried holding a newborn female baby (ALM062) against the right side of her chest. As the skeletal superposition indicates, the synchronic inhumation of the two bodies and the genetic analysis suggests a mother/daughter relationship (Fig. S5A), where complications in the period after childbirth could be considered the likely cause of death. It is noteworthy that the child carried the 7 Vol.:(0123456789) Scientific Reports | (2022) 12:22415 | https://doi.org/10.1038/s41598-022-25975-9 www.nature.com/scientificreports/ aneuploid XXX-syndrome 8, but this condition is unlikely to have caused the untimely death of both the baby and her mother 42. The combination of adult/subadult individuals in double burials (25%) is relatively uncommon at El Argar sites, and the example from tomb AY21 might hint at exceptional circumstances involving a close genetic relationship. This might be the case for tomb AY85, in which another female neonate, whose sex has been determined genetically (ALM079), was found in the arms of an adult female (ALM066) and in a position remarkably similar to tomb AY21. Unfortunately, the sample of the adult female did not produce sufficient genetic data and therefore we could not ascertain a putative mother/daughter relationship. Conversely, tomb BA6 at La Bastida shows that other scenarios are possible. Here, a 25–30-year-old male (BAS002) was buried alongside a newborn boy (BAS026), but the two were not genetically related (Dataset S1.2). It is important to note that this burial cannot be considered simultaneous as in the other two cases, since part of the pithos rim broke when the tomb was reopened and the fragments ended up on top of the adult pelvis and below the neonate skeleton, thus providing evidence of successive inhumations. However, radiocarbon dates were not statistically different at the 95% confidence level (Supplementary 5). It is possible that this burial was meant to represent a father/son relationship, but whether the adult male buried in BA6 would be aware of the real biological fatherhood or not (as stepfather and therefore social kin) remains an open question. Double burials of children. We successfully recovered DNA from the only double burial at La Almoloya (AY30) with two children. The grave consisted of a small pit, in which a female toddler (ALM030) of 14–17months was first buried, followed later by an 8or 9-year-old girl (ALM031). There were no grave goods associated with ALM031, and from the funerary context we infer that she was buried after ALM030, as her skeleton was found fully articulated and partly on top of the jumbled post-cranium of the younger girl ALM030. We detected a halfsibling relationship between these two girls on their father’s side (Fig.3, Supplementary 3), which indicated that the adult male ALM039 from the wealthiest grave AY38 of La Almoloya, located in the nearby palatial building, was the father of both. It is noteworthy that the adult female ALM038, buried alongside this man, was the mother of only one of the girls (ALM030), and that we have not identified the biological mother of ALM031 among the successfully typed individuals. The archaeological context does not provide clues as to whether the two mothers lived at the same time or not, nor whether this case represents an example of serial monogamy, or, alternatively, polygamy. However, the fact that the half-sisters were entombed together reflects awareness (on the part of the people who buried them) of the kin relationship between the two children, irrespective of their different biological mothers, and very likely also the acknowledgement of fatherhood on behalf of ALM039. However, it is also possible that these unions were temporal and dissolvable. The instances in which siblings were identified genetically also represent variable archaeological contexts and situations open to interpretation. We also detected two siblings buried together in tomb BA23 from La Bastida, which, like AY30, also dates to the late Argaric phase (Supplementary 4). A 9-to-11-month-old girl BAS017 was buried in a ceramic vessel, followed by her brother BAS018, who died shortly after at roughly the same age. Conversely, in another case of siblings from La Almoloya, two boys (ALM080 and ALM081) were buried very close to each other but in separate graves (AY88 and AY89, respectively) (Fig. S5). As a result, we observe that double tombs containing at least one child feature close biological relationships, except for the case of the adult and newborn male found at La Bastida (BA6), which deviates from the double burials of adults. Genetic relationships beyond double tombs. We also observed several biological relationships between individuals buried in single tombs and therefore explored the degrees of relatedness in the light of chronological and spatial distances. Phase 3 at La Almoloya is characterized by a network of housing complexes that were built around 1750cal BCE, and which form a large part of the structures visible today (Fig.2A). However, the layout of the preceding phase 2 was largely dismantled by the urbanization efforts of phase 3. Thus, building complexes cannot be used as a general background, and it is advisable to operate with raw distances only. To analyze the spatial distribution of biologically related individuals, we plotted the physical distances between all 1stand 2nd-degree related pairs of individuals (Fig.2A). We find that most of the individuals with close parental links were buried less than 5m apart from each other. Interestingly, half-siblings (biologically 2nd-degree relatives) are spatially as close as full siblings (1st-degree relatives), while all other 2nd-degree related individuals (uncle-aunt/nephew-niece and grandparent-grandchild relationships) are separated by 19–32m, and are often buried under the floors of different buildings of phase 3. We documented a case of full siblings (ALM080 and ALM081) located in separate but close pithoi graves without grave goods. Both male individuals died prematurely, one at the age of 14–20months (ALM080) and the other at the age of 18–24months (ALM081), and while the time elapsed between their deaths remains unknown, this situation suggests the intentional placing of the two brothers in a nearby space (Fig. S5). As mentioned above, other full siblings from La Bastida (genetically male and female) were found buried together in tomb BA23 (Supplementary 4). These two examples may reflect social ties among subadult siblings regardless of their biological sex. We detected a possible half-sibling relationship on the father’s side between ALM068 (a 14–16-month-old female baby from tomb AY8) and ALM078 (a 14–16-month-old male from tomb AY23 interred sometime later), buried in separate graves but within the same housing complex. The mother of ALM068 was buried in a separate tomb (AY17-ALM077), close to her daughter but not to the boy (ALM078), to whom she is biologically unrelated. Another possible, but perhaps less plausible interpretation for the 2nd-degree relationship between the two children is that the boy (ALM078) was the uncle of the girl (ALM068) on her father’s side (albeit one generation younger), as he is not related to her mother, ALM077 (Fig. S5). 8 Vol:.(1234567890) Scientific Reports | (2022) 12:22415 | https://doi.org/10.1038/s41598-022-25975-9 www.nature.com/scientificreports/ Another half-sibling relationship on the father’s side can be suggested for ALM046 (a 14–18-month-old boy), buried in grave AY13, and ALM047 (a 6–7-month-old male infant) buried in grave AY14, none of which had grave goods. In this case, we found neither the father nor the mother among the successfully genotyped individuals, and we cannot completely rule out the possibility of an uncle/nephew relationship. However, these individuals were buried close to one another, as was also the case with other pairs of siblings, which strongly hints at specific social and familial ties (Supplementary 3). In summary, an aunt-uncle/niece-nephew relationship cannot be excluded in cases in which two children are related in the 2nd degree. It is worthwhile noting that half-siblings, which would in every case be linked via the paternal line, make polygamy (polygyny) and serial monogamy plausible practices to consider. However, we also found other 2nd-degree relationships between an adult and a subadult for which we cannot discard an avuncular relation, such as ALM004 (adult female) and ALM075 (infant female), or ALM019 (adult female) and ALM069 (infant male) (Supplementary 3). Lastly, we were able to infer more distant relatives by calculating the number and fraction of segments in the 1240k SNP data that are identical-by-descent (IBD) in individuals with > 600,000 SNPs after imputation (“Materials and methods”, Supplementary 2). This method not only allowed us to confirm and distinguish between close 1stand 2nd-degree relationships but also to estimate biological relatedness up to the 6th–7th degree, by which we were able to connect three of the seven main pedigrees reconstructed at La Almoloya (Dataset S1.7, Supplementary 3). Inferring kinship practices. Following the individual-based evaluation of biological relatedness at La Almoloya, we compared the structure of the reconstructed pedigrees from all related individuals and looked for links across generations that would signal lineality or inheritance along preferential parental lines. Here, we observed that all reconstructed pedigrees are linked through the paternal side and, in one case, the male lineage can be traced over at least five generations (Fig.3, Supplementary 3). In addition, in all other cases of 2ndand 3rd-degree relationships (six 2nd-degree pairs), for which the pedigree could not be fully established or extended due to missing 1st-degree related individuals, we observe that the possible alternative pedigrees can also only be explained through the paternal line (Supplementary 3). All 1st-degree relationships among adults involved at least one adult male (3 out of 19 adult males analyzed) (Fig.4). No adult male has an adult daughter, sister, brother, or adult half-siblings also buried at the site. The few 2nd-degree relationships involving adults were all also between males (4 out of 19 adult males analyzed) (Fig.4). Conversely, we found no 1stor 2nd-degree relationships between adult women (0 out of 30 adult women analyzed). Women related in the 1st degree at the site were mothers of either girls (AY21/2-ALM062, AY30/1ALM0030, AY8-ALM068) or adult males (AY16-ALM034, AY27/1-ALM058 and AY42/1-ALM052), but not boys. These women were not related to any other adult women (Fig.4) and had no parents at the site. The same holds true for 2nd-degree related females, then considered integrated lineage females, who were found to be aunts and/or grandmothers (AY58-ALM004, AY87-ALM019, AY26/2-ALM086) of both girls and boys, but, again, never related to adult women (Fig.4). These results obtained by reconstructing the pedigrees are in line with results that have already been reported at the meta-level in8, where it was described that males of La Almoloya had more close relatives at the site than females. This observation was made based on significantly higher observed f3-statistics for f3 (male, male; Mbuti) than f3 (female, male; Mbuti) than f3 (female, female; Mbuti) (after excluding all 1stand 2nd-degree related pairs). Although the f3-outgroup statistic is used at the population level to measure shared genetic drift between two populations after the split from a common outgroup, it has been also useful to identify 1st-degree relatives as they share half of their genomes and thus, will report higher f3-values4,8. Examining the paternal lineages, we observe a higher residential stability, not only at the site but also in some specific housing complexes (i.e., close proximity) (Fig.2A). A prime example is ALM034/AY16, an adult male buried close to his parents, ALM048/AY22-1 and ALM049/AY22-2. A similar scenario could be inferred for female ALM086/AY26-2, buried in an adult double burial close to her adult son ALM058/AY27-1. Unfortunately, we did not obtain sufficient aDNA from the partner buried with ALM086/AY26-1 to prove the biological fatherhood between him and ALM058/AY27-1 (Supplementary 3, Fig.S5). Finally, another example of crossgenerational paternal lineages buried closer in space are ALM015/AY80-1 and ALM016/AY80-2, an adult double burial, which also contained the skull of their adult great-grandson ALM017/AY80-0 (Fig.3, Supplementary 3). Other sources of information to infer lineality and locality can be gleaned from uniparentally inherited markers, such as mitochondrial DNA (mtDNA) and Y-chromosomal haplogroups. Irrespective of the varying genetic resolution, the finding of only one single Y-chromosome lineage in La Almoloya (R1b-P312 > Z195), which is also the predominant lineage across Iberia, is remarkable, but cannot be used to resolve relationship patterns at an intra-site level and thus suggests a much more common practice at a broader scale or a small/non-diverse source population of Y chromosome diversity. The diversity of the mtDNA is also similar to the diversity observed in Iberia in the preceding periods 43, with the exception of one female individual carrying mtDNA haplogroup R0a, which has not been reported to date from Iberia (Dataset S1.2). Aside from close relationships within La Almoloya, we also found a close relationship between ALM034/ AY16 and a 40–50-year-old female from Lorca, buried in Madres Mercedarias Tomb 4_1 (MMI003), another Argaric site about 50km away. Due to the low coverage of MMI003, the biological relatedness tests returned an intermediate value between 1stand 2nd-degree and thus need to be interpreted with caution. In the case of a 1st-degree relationship, MMI003 would be a direct example of female exogamy. In the case of a 2nd-degree relationship, the type of mobility would be unspecific as the parent leaving La Almoloya could have been either the father or the mother of the female from Lorca (Fig.3, Supplementary 3). 9 Vol.:(0123456789) Scientific Reports | (2022) 12:22415 | https://doi.org/10.1038/s41598-022-25975-9 www.nature.com/scientificreports/ Using IBD analyses, we also found three 6th–7th-degree inter-site relationships involving pairs of males and female and male individuals from La Almoloya and La Bastida (Dataset S1.7), which connect the networks of biological relatives across both El Argar sites. In addition, we found between-site connections between individuals from phase 3 of La Almoloya and La Horna (LHO), a Valencian BA site 44,45. This finding highlights the power to detect long-distance relationships through intensive sampling schemes and emphasizes the extended networks within El Argar, but also sheds light on the political and economic relations with neighboring societies46 (Dataset S1.7, Fig.S4). The combined view of the results leans towards the practice of female exogamy and patrilocality, in which young females moved to a different residence to build new relationships. The adult females buried in double graves provide support for these practices as they have no parents buried at the site and, apart from their offspring, also no other adult relatives, which suggests that they came from outside the community and were integrated through their union with local males, and can thus be considered mates of lineage males. Importantly, the fact that we do not find 1stor 2nd-degree relationships between adult women at La Almoloya suggests that this practice was reciprocal and that young females from La Almoloya also moved to other sites. Patrilocality does not necessarily imply the absence of mobility of adult males. In fact, our results also support substantial mobility for both sexes as shown by the presence of fewer 2nd-degree than 1st-degree relatives at the site. However, the ability to trace male lineages through generations by the presence of adult male offspring, but not female adult offspring (Fig.4B), supports patrilocality despite male and female mobility. The integration of genetic, demographic, and other contextual data sheds further light on the social organization and kinship practices of the Argaric community. Results of the genetic and anthropological sex determination indicate a slight excess of males (11 males vs. 8 females) among subadults. By contrast, the number of adult women (N = 53) exceeds the number of adult men (N = 32), resulting in a sex ratio of 1.65 in favor of Figure4. Overview of genetic sex and age at death determinations and total numbers of observed relationships per category and long-distance relatives outside La Almoloya. (A) Simplified age classes of the individuals analyzed from La Almoloya: subadult (including infant (0–3years) and child (3–12years)) and adult (including young adult (20–35years), middle adult (35–50years), and old adult (50+ years)56) females and males. Of note, adolescent individuals (12–20years) were not found at the site; (B) total number of 1st- (pink) and 2nd-degree (purple) relatives between age and sex classes as summarized in (A). Numbers reflect the number of links in the pedigrees between age/sex classes and numbers inside symbols reflect the number of links within each class. The graph illustrates the absence of either 1stor 2nd-degree relationships among adult females; (C) Long-distance relatives (6–7th degree) as indicated by shared IBD-blocks between individuals from La Almoloya and other BA archaeological sites. The map was created using QGIS 3.12 (https:// qgis. org/ en/ site/) and uses Natural Earth vector map data from (https:// www. natur alear thdata. com/ downl oads/).