Expansion of domesticated goat echoes expansion of early farmers

goat-neolithic

New paper (behind paywall) Ancient goat genomes reveal mosaic domestication in the Fertile Crescent, by Daly et al. Science (2018) 361(6397):85-88.

Interesting excerpts (emphasis mine):

Thus, our data favor a process of Near Eastern animal domestication that is dispersed in space and time, rather than radiating from a central core (3, 11). This resonates with archaeozoological evidence for disparate early management strategies from early Anatolian, Iranian, and Levantine Neolithic sites (12, 13). Interestingly, our finding of divergent goat genomes within the Neolithic echoes genetic investigation of early farmers. Northwestern Anatolian and Iranian human Neolithic genomes are also divergent (14–16), which suggests the sharing of techniques rather than large-scale migrations of populations across Southwest Asia in the period of early domestication. Several crop plants also show evidence of parallel domestication processes in the region (17).

PCA affinity (Fig. 2), supported by qpGraph and outgroup f3 analyses, suggests that modern European goats derive from a source close to the western Neolithic; Far Eastern goats derive from early eastern Neolithic domesticates; and African goats have a contribution from the Levant, but in this case with considerable admixture from the other sources (figs. S11, S16, and S17 and tables S26 and 27). The latter may be in part a result of admixture that is discernible in the same analyses extended to ancient genomes within the Fertile Crescent after the Neolithic (figs. S18 and S19 and tables S20, S27, and S31) when the spread of metallurgy and other developments likely resulted in an expansion of inter-regional trade networks and livestock movement.

goat-middle-east
Maximumlikelihood phylogeny and geographical distributions of ancient mtDNA haplogroups. (A) A phylogeny placing ancient whole mtDNA sequences in the context of known haplogroups. Symbols denoting individuals are colored by clade membership; shape indicates archaeological period (see key). Unlabeled nodes are modern bezoar and outgroup sequence (Nubian ibex) added for reference.We define haplogroup T as the sister branch to the West Caucasian tur (9). (B and C) Geographical distributions of haplogroups show early highly structured diversity in the Neolithic period (B) followed by collapse of structure in succeeding periods (C).We delineate the tiled maps at 7250 to 6950 BP, a period >bracketing both our earliest Chalcolithic sequence (24, Mianroud) and latest Neolithic (6, Aşağı Pınar). Numbered archaeological sites also include Direkli Cave (8), Abu Ghosh (9), ‘Ain Ghazal (10), and Hovk-1 Cave (11) (table S1) (9).

Our results imply a domestication process carried out by humans in dispersed, divergent, but communicating communities across the Fertile Crescent who selected animals in early millennia, including for pigmentation, the most visible of domestic traits.

Related

Bayesian estimation of partial population continuity by using ancient DNA and spatially explicit simulations

europe-palaeolithic-neolithic

Open access Bayesian estimation of partial population continuity by using ancient DNA and spatially explicit simulations, by Silva et al., Evolutionary Applications (2018).

Abstract (emphasis mine):

The retrieval of ancient DNA from osteological material provides direct evidence of human genetic diversity in the past. Ancient DNA samples are often used to investigate whether there was population continuity in the settlement history of an area. Methods based on the serial coalescent algorithm have been developed to test whether the population continuity hypothesis can be statistically rejected by analysing DNA samples from the same region but of different ages. Rejection of this hypothesis is indicative of a large genetic shift, possibly due to immigration occurring between two sampling times. However, this approach is only able to reject a model of full continuity model (a total absence of genetic input from outside), but admixture between local and immigrant populations may lead to partial continuity. We have recently developed a method to test for population continuity that explicitly considers the spatial and temporal dynamics of populations. Here we extended this approach to estimate the proportion of genetic continuity between two populations, by using ancient genetic samples. We applied our original approach to the question of the Neolithic transition in Central Europe. Our results confirmed the rejection of full continuity, but our approach represents an important step forward by estimating the relative contribution of immigrant farmers and of local hunter‐gatherers to the final Central European Neolithic genetic pool. Furthermore, we show that a substantial proportion of genes brought by the farmers in this region were assimilated from other hunter‐gatherer populations along the way from Anatolia, which was not detectable by previous continuity tests. Our approach is also able to jointly estimate demographic parameters, as we show here by finding both low density and low migration rate for pre‐Neolithic hunter‐gatherers. It provides a useful tool for the analysis of the numerous aDNA datasets that are currently being produced for many different species.

central-european-neolithic
A) Different zones defined for computing proportions of ancestry in Central Europeans 4,500 BP. B) Schematic representation of various population contributions. C) Mean proportions of ancestry from the various PHG zones (A+B+C+D) in Central European populations from zone A at the end of the Neolithic transition 4,500 BP, computed for autosomal and mitochondrial markers.

Relevant excerpts:

Our results are in general accordance with two distinct ancestry components that have previously been detected at the continental scale by Lazaridis, Patterson et al. (2014): the “early European farmer” (EEF), which corresponds here to the NFA from Anatolia (zone C in Figure 3), and the “West European hunter-gatherer” (WHG), which corresponds here to the PHG from zones A and B in Figure 3. Notably, the contribution of an Ancient North Eurasians (ANE) component is not included in our model as we did not consider potential post-Neolithic immigration waves, which could have contributed to the modern European genetic pool, such as the wave that came from the Pontic steppes and was associated with the Yamnaya culture (Haak, Lazaridis et al. 2015). Without considering the ANE ancestry component, our estimate of the autosomal genetic contribution of Early farmers to the gene pool of Central European populations (25%) tends to be lower than the EEF ancestry estimated in most modern Western European populations, but is of the same order than the estimations in modern Estonians and in the ancient Late Neolithic genome “Karsdorf” from Germany (Lazaridis, Patterson et al. 2014, Haak, Lazaridis et al. 2015). Note that the contribution of hunter-gatherers to Neolithic communities appears to be variable in different regions of Europe (Skoglund, Malmstrom et al. 2012, Brandt, Haak et al. 2013, Lazaridis, Patterson et al. 2014), while we computed an average value for Central Europe. Moreover, we computed the ancestry of the two groups at the end of the Neolithic period while previous studies estimated it in modern times. Finally, previous studies used molecular information to directly estimate admixture proportions, while we use molecular information to estimate the model parameters and, then, we computed the expected genetic contributions of both groups using the best parameters, without using molecular information during this second step. Model assumptions may thus influence the inferences on the relative genetic contribution of both groups. In particular, we made the assumption of a uniform expansion of NFA with constant and similar assimilation of PHG over the whole continent but spatio-temporally heterogeneous environment, variable assimilation rate and long distance dispersal may have played an important role. The effects of those factors should be investigated in future studies.

Iberian prehistoric migrations in Genomics from Neolithic, Chalcolithic, and Bronze Age

iberia-neolithic-bronze-age

New open access paper Four millennia of Iberian biomolecular prehistory illustrate the impact of prehistoric migrations at the far end of Eurasia, by Valdiosera, Günther, Vera-Rodríguez, et al. PNAS (2018) published ahead of print.

Abstract (emphasis mine)

Population genomic studies of ancient human remains have shown how modern-day European population structure has been shaped by a number of prehistoric migrations. The Neolithization of Europe has been associated with large-scale migrations from Anatolia, which was followed by migrations of herders from the Pontic steppe at the onset of the Bronze Age. Southwestern Europe was one of the last parts of the continent reached by these migrations, and modern-day populations from this region show intriguing similarities to the initial Neolithic migrants. Partly due to climatic conditions that are unfavorable for DNA preservation, regional studies on the Mediterranean remain challenging. Here, we present genome-wide sequence data from 13 individuals combined with stable isotope analysis from the north and south of Iberia covering a four-millennial temporal transect (7,500–3,500 BP). Early Iberian farmers and Early Central European farmers exhibit significant genetic differences, suggesting two independent fronts of the Neolithic expansion. The first Neolithic migrants that arrived in Iberia had low levels of genetic diversity, potentially reflecting a small number of individuals; this diversity gradually increased over time from mixing with local hunter-gatherers and potential population expansion. The impact of post-Neolithic migrations on Iberia was much smaller than for the rest of the continent, showing little external influence from the Neolithic to the Bronze Age. Paleodietary reconstruction shows that these populations have a remarkable degree of dietary homogeneity across space and time, suggesting a strong reliance on terrestrial food resources despite changing culture and genetic make-up.

iberia-admixture
(A) f4 statistics testing affinities of prehistoric European farmers to either early Neolithic Iberians or central Europeans, restricting these reference populations to SNP-captured individuals to avoid technical artifacts driving the affinities. The boxplots in A show the distributions of all individual f4 statistics belonging to the respective groups. The signal is not sensitive to the choice of reference populations and is not driven by hunter-gatherer–related admixture (Datasets S4 and S5). (B) Estimates of ancestry proportions in different prehistoric Europeans as well as modern southwestern Europeans. Individuals from regions of Iberia were grouped together for the analysis in A and B to increase sample sizes per group and reduce noise

Conclusion:

We present a comprehensive biomolecular dataset spanning four millennia of prehistory across the whole Iberian Peninsula. Our results highlight the power of archaeogenomic studies focusing on specific regions and covering a temporal transect. The 4,000 y of prehistory in Iberia were shaped by major chronological changes but with little geographic substructure within the Peninsula. The subtle but clear genetic differences between early Neolithic Iberian farmers and early Neolithic central European farmers point toward two independent migrations, potentially originating from two slightly different source populations. These populations followed different routes, one along the Mediterranean coast, giving rise to early Neolithic Iberian farmers, and one via mainland Europe forming early Neolithic central European farmers. This directly links all Neolithic Iberians with the first migrants that arrived with the initial Mediterranean Neolithic wave of expansion. These Iberians mixed with local hunter-gatherers (but maintained farming/pastoral subsistence strategies, i.e., diet), leading to a recovery from the loss of genetic diversity emerging from the initial migration founder bottleneck. Only after the spread of Bell Beaker pottery did steppe-related ancestry arrive in Iberia, where it had smaller contributions to the population compared with the impact that it had in central Europe. This implies that the two prehistoric migrations causing major population turnovers in central Europe had differential effects at the southwestern edge of their distribution: The Neolithic migrations caused substantial changes in the Iberian gene pool (the introduction of agriculture by farmers) (6, 9, 11, 13, 24), whereas the impact of Bronze Age migrations (Yamnaya) was significantly smaller in Iberia than in north-central Europe (24). The post-Neolithic prehistory of Iberia is generally characterized by interactions between residents rather than by migrations from other parts of Europe, resulting in relative genetic continuity, while most other regions were subject to major genetic turnovers after the Neolithic (4, 6, 7, 9, 25, 48). Although Iberian populations represent the furthest wave of Neolithic expansion in the westernmost Mediterranean, the subsequent populations maintain a surprisingly high genetic legacy of the original pioneer farming migrants from the east compared with their central European counterparts. This counterintuitive result emphasizes the importance of in-depth diachronic studies in all parts of the continent.

Related:

Migration vs. Acculturation models for Aegean Neolithic in Genetics — still depending strongly on Archaeology

aegean-neolithic-anatolia

Recent paper in Proceedings of the Royal Society B: Archaeogenomic analysis of the first steps of Neolithization in Anatolia and the Aegean, by Kılınç et al. (2017).

Abstract:

The Neolithic transition in west Eurasia occurred in two main steps: the gradual development of sedentism and plant cultivation in the Near East and the subsequent spread of Neolithic cultures into the Aegean and across Europe after 7000 cal BCE. Here, we use published ancient genomes to investigate gene flow events in west Eurasia during the Neolithic transition. We confirm that the Early Neolithic central Anatolians in the ninth millennium BCE were probably descendants of local hunter–gatherers, rather than immigrants from the Levant or Iran. We further study the emergence of post-7000 cal BCE north Aegean Neolithic communities. Although Aegean farmers have frequently been assumed to be colonists originating from either central Anatolia or from the Levant, our findings raise alternative possibilities: north Aegean Neolithic populations may have been the product of multiple westward migrations, including south Anatolian emigrants, or they may have been descendants of local Aegean Mesolithic groups who adopted farming. These scenarios are consistent with the diversity of material cultures among Aegean Neolithic communities and the inheritance of local forager know-how. The demographic and cultural dynamics behind the earliest spread of Neolithic culture in the Aegean could therefore be distinct from the subsequent Neolithization of mainland Europe.

The analysis of the paper highlights two points regarding the process of Neolithisation in the Aegean, which is essential to ascertain the impact of later Indo-European migrations of Proto-Anatolian and Proto-Greek and other Palaeo-Balkan speakers(texts partially taken verbatim from the paper):

  • The observation that the two central Anatolian populations cluster together to the exclusion of Neolithic populations of south Levant or of Iran restates the conclusion that farming in central Anatolia in the PPN was established by local groups instead of immigrants, which is consistent with the described cultural continuity between central Anatolian Epipalaeolithic and Aceramic communities. This reiterates the earlier conclusion that the early Neolithisation in the primary zone was largely a process of cultural interaction instead of gene flow.
aegean-neolithic-pca
Principal component analysis (PCA) with modern and ancient genomes. The eigenvectors were calculated using 50 modern west Eurasian populations, onto which genome data from ancient individuals were projected. The gray circles highlight the four ancient gene pools of west Eurasia. Modern-day individuals are shown as gray points. In the Near East, Pre-Neolithic (Epipaleolithic/Mesolithic) and Neolithic individuals genetically cluster by geography rather than by cultural context. For instance, Neolithic individuals of Anatolia cluster to the exclusion of individuals from the Levant or Iran). In Europe, genetic clustering reflects cultural context but not geography: European early Neolithic individuals are genetically distinct from European pre-Neolithic individuals but tightly cluster with Anatolians. PPN: Pre-Pottery/Aceramic Neolithic, PN: Pottery Neolithic, Tepecik: Tepecik-Çiftlik (electronic supplementary material, table S1 lists the number of SNPs per ancient individual).
  • The realisation that there are still two possibilities regarding the question of whether Aegean Neolithisation (post-7000 cal BC) involved similar acculturation processes, or was driven by migration similar to Neolithisation in mainland Europe — a long-standing debate in Archaeology:
    1. Migration from Anatolia to the Aegean: the Aegean Neolithisation must have involved replacement of a local, WHG-related Mesolithic population by incoming easterners. Central Anatolia or south Anatolia / north Levant (of which there is no data) are potential origins of the components observed. Notably, the north Aegeans – Revenia (ca. 6438-6264 BC) and Barcın (ca. 6500-6200 BC) – show higher diversity than the central Anatolians, and the population size of Aegeans was larger than that of central Anatolians. The lack of WHG in later samples indicates that they must have been fully replaced by the eastern migrant farmers.
    2. Adoption of Neolithic elements by local foragers: Alternatively, the Aegean coast Mesolithic populations may have been part of the Anatolian-related gene pool that occupied the Aegean seaboard during the Early Holocene, in an “out-of-the-Aegean hypothesis. Following the LGM, Aegean emigrants would have dispersed into central Anatolia and established populations that eventually gave rise to the local Epipalaeolithic and later Neolithic communities, in line with the earliest direct evidence for human presence in central Anatolia ca 14 000 cal BCE
  • On the archaeological evidence (excerpt):

    Instead of a single-sourced colonization process, the Aegean Neolithization may thus have flourished upon already existing coastal and interior interaction networks connecting Aegean foragers with the Levantine and central Anatolian PPN populations, and involved multiple cultural interaction events from its early steps onward [16,20,64,74]. This wide diversity of cultural sources and the potential role of local populations in Neolithic development may set apart Aegean Neolithization from that in mainland Europe. While Mesolithic Aegean genetic data are awaited to fully resolve this issue, researchers should be aware of the possibility that the initial emergence of the Neolithic elements in the Aegean, at least in the north Aegean, involved cultural and demographic dynamics different than those in European Neolithization.

    Featured image, from the article: “Summary of the data analyzed in this study. (a) Map of west Eurasia showing the geographical locations and (b) timeline showing the time period (years BCE) of ancient individuals investigated in the study. Blue circles: individuals from pre-Neolithic context; red triangles: individuals from Neolithic contexts”.

    Related: