Expansion of haplogroup G2a in Anatolia possibly associated with the Mature Aceramic period

anatolian-hunter-gatherer-sampling

Preprint Late Pleistocene human genome suggests a local origin for the first farmers of central Anatolia, by Feldman et al. bioRxiv (2018).

Interesting excerpts (emphasis mine):

Anatolian hunter-gatherers experienced climatic changes during the last glaciation and inhabited a region that connects Europe to the Near East. However, interactions between Anatolia and Southeastern Europe in the later Upper Palaeolithic/Epipalaeolithic are so far not well documented archaeologically. Interestingly, a previous genomic study showed that present-day Near-Easterners share more alleles with European hunter-gatherers younger than 14,000 BP (‘Later European HG’) than with earlier ones (‘Earlier European HG’). With ancient genomic data available, we could directly compare the Near-Eastern hunter-gatherers (AHG and Natufian) with the European ones. As is the case for present-day Near-Easterners, the Near-Eastern hunter-gatherers share more alleles with the Later European HG than with the Earlier European HG, shown by the significantly positive statistic D(Later European HG, Earlier European HG; AHG/Natufian, Mbuti). Among the Later European HG, recently reported Mesolithic hunter-gatherers from the Balkan peninsula, which geographically connects Anatolia and central Europe (‘Iron Gates HG’), are genetically closer to AHG when compared to all the other European hunter-gatherers, as shown in the significantly positive statistic D(Iron_Gates_HG, European hunter-gatherers; AHG, Mbuti/Altai). Iron Gates HG are followed by Epigravettian and Mesolithic individuals from Italy and France (Villabruna and Ranchot respectively) as the next two European hunter-gatherers genetically closest to AHG. Iron Gates HG have been suggested to be genetically intermediate between WHG and eastern European hunter-gatherers (EHG) with an additional unknown ancestral component.

anatolian-hunter-gatherer-pca
Ancient genomes (marked with color-filled symbols) projected onto the principal components 5 computed from present-day west Eurasians (grey circles) (fig. S4). The geographic location of each ancient group is marked in (A). Ancient individuals newly reported in this study are additionally marked with a black dot inside the symbol

We find that Iron Gates HG can be modeled as a three-way mixture of Near-Eastern hunter-gatherers (25.8 ± 5.0 % AHG or 11.1 ± 2.2 % Natufian), WHG (62.9 ± 7.4 % or 78.0 ± 4.6 % respectively) and EHG (11.3 ± 3.3 % or 10.9 ± 3 % respectively). The affinity detected by the above D-statistic can be explained by gene flow from Near-Eastern hunter-gatherers into the ancestors of Iron Gates or by a gene flow from a population ancestral to Iron Gates into the Near-Eastern hunter-gatherers as well as by a combination of both. To distinguish the direction of the gene flow, we examined the Basal Eurasian ancestry 5 component (α), which is prevalent in the Near East but undetectable in European hunter-gatherers. Following a published approach, we estimated α to be 24.8 ± 5.5 % in AHG and 38.5 ± 5.0 % in Natufians, consistent with previous estimates for the latter. Under the model of unidirectional gene flow from Anatolia to Europe, 6.4 % is expected for α of Iron Gates by calculating (% AHG in Iron Gates HG) × (α in AHG). However, Iron Gates can be modeled without any Basal Eurasian ancestry or with a non-significant proportion of 1.6 ± 2.8 %, suggesting that unidirectional gene flow from the Near East to Europe alone is insufficient to explain the extra affinity between the Iron Gates HG and the Near-Eastern hunter-gatherers. Thus, it is plausible to assume that prior to 15,000 years ago there was either a bidirectional gene flow between populations ancestral to Southeastern Europeans of the early Holocene and Anatolians of the late glacial or a dispersal of Southeastern Europeans into the Near East. Presumably, this Southeastern European ancestral population later spread into central Europe during the post-last-glacial maximum (LGM) period, resulting in the observed late Pleistocene genetic affinity between the Near East and Europe.

near-eastern-european-hg
Basal Eurasian ancestry proportions (α) as a marker for Near-Eastern gene flow. Mixture proportions inferred by qpAdm for AHG and the Iron Gates HG are schematically represented. The lower schematic shows the expected α in Iron Gates HG under 10 assumption of unidirectional gene flow, inferred from α in the AHG source population. The observed α for Iron Gates HG is considerably smaller than expected thus, the unidirectional gene flow from the Near East to Europe is not sufficient to explain the above affinity.

While ancestry is not always relevant to distinguish certain population movements (see here), especially – as in this case – when there are few samples (thus neither geographically nor chronologically representative) and no previous model to test, it seems that ancestry and Y-DNA show a great degree of continuity in Anatolia since the Palaeolithic until the Neolithic, at least in the sampled regions. C1a2 appears in Europe since ca. 40,000 years ago (viz. Kostenki, Goyet, Vestonice, etc., and later emerges again in the Balkans after the Anatolian Neolithic expansion, probably a resurge of European groups).

The potential transition of a G2a-dominated agricultural society – that is later prevalent in Anatolian and European farmers – may have therefore happened during the Aceramic III period (ca. 8000 BC), a process of haplogroup expansion probably continuing through the early part of the Pottery Neolithic, as the society based on kinship appeared (Rosenberg and Erim-Özdoğan 2011). There is still much to know about the spread of ceramic technology and southwestern Asia domesticate complex, though.

anatolian-palaeolithic-hg

Without a proper geographical sampling, representative of previous and posterior populations, it is impossible to say. But the expansion of R1b-L754 through Anatolia to form part of the Villabruna cluster (and also the Iron Gates HG) seems perfectly possible with this data, although this paper does not help clarify the when or how. We have seen significant changes in ancestry happen within centuries with expanding populations admixing with locals. Palaeolithic sampling – like this one – shows few individuals scattered geographically over thousands of km and chronologically over thousands of years…

Related

Polygyny as a potential reason for Y-DNA bottlenecks among agropastoralists

polygyny-estimates

Open access Greater wealth inequality, less polygyny: rethinking the polygyny threshold model by Ross et al. Journal of the Royal Society Interface (2018).

Interesting excerpts, from the discussion (emphasis mine):

We use cross-cultural data and a new mutual mate choice model to propose a resolution to the polygyny paradox. Following Oh et al. [17], we extend the standard polygyny threshold model to a mutual mate choice model that accounts for both female supply to, and male demand for, polygynous matchings, in the light of the importance of, and inequality in, rival and non-rival forms of wealth. The empirical results presented in figures 5 and 6 demonstrate two phenomena that are jointly sufficient to generate a transition to more frequent monogamy among populations with a co-occurring transition to a more unequal, highly stratified, class-based social structure. In such populations, fewer men can cross the wealth threshold required to obtain a second wife, and those who do may be fabulously wealthy, but—because of diminishing marginal fitness returns to increasing number of marriages—do not acquire wives in full proportion to their capacity to support them with rival wealth. Together, these effects reduce the population-level fraction of wives in polygynous marriages.

Our model demonstrates that a low population-level frequency of polygyny will be an equilibrium outcome among fitness maximizing males and females in a society characterized by a large class of wealth-poor peasants and a small class of exceptionally wealthy elite. Our mutual mate choice model thus provides an empirically plausible resolution to the polygyny paradox and the transition to monogamy which co-occurred with the rise of highly unequal agricultural populations.

polygyny-pastoralists
(a) Mean frequency of married women who are married polygynously by production system (+2 s.e.) using the Standard Cross-Cultural Sample [30]. Rates of polygyny are measured with variable ]872, per cent of wives with co-wives. (b) Rates of monogamy and polygyny by production system are measured with variable ]861, the standard polygamy code. Data on subsistence come from variable ]858, categorized subsistence. In general, agricultural populations show reduced rates of polygyny and increased rates of monogamy relative to other subsistence systems. See electronic supplementary material for more information. (c) Gini of wealth by production system in our sample.

The reasons for this decrease in marginal fitness returns are explained as either a) a potential missing of important rival forms of wealth in the statistical model, or b) one or more of the following reasons:

  • [A] male’s time and attention are rival inputs to his own fitness (…) A single rich man will have to defend his 10 wives from nine unmarried men on average.”As the wealth ratio grows even more skewed, this situation could become increasingly difficult to manage (e.g. requiring the use of eunochs to defend harems [74]).
  • A related possibility is that a growing number of unmarried men could socially censure wealthy polygynous males, imposing costs on them that reduce male demand for and/or female supply to polygynous marriage [23,24]. (…)
  • A third possibility is that sexually transmitted infection (STI) burden [22,75] could diminish returns to polygyny, if polygyny enhances infection rates [76,77]. (…)
  • Finally, impediments to cooperation or even outright conflict among co-wives can be greater as the number of wives increases. Interference competition among co-wives could impose significant fitness costs in settings where effective child rearing benefits from cooperation [79,80].(…)
polygyny-agropastoralists
between the Gini coefficient on completed rival wealth and per cent completed female polygyny.

I have previously argued against some reasons traditionally given to explain the replacement of native male populations after migrations (i.e. polygyny, slavery, targeted male extermination, etc.), because I believe that a gradual successful expansion of patrilineal clans over some generations based on wealth alone is enough to explain the obvious Y-DNA bottlenecks that happened in many different prehistoric and historic cultures (especially among steppe pastoralists, including Indo-Europeans).

I realize that I haven’t really used any study to support my opinion, though, and data from modern and ancient pastoralists from different regions seem to contradict it, so maybe ancient DNA can show that Indo-Europeans had often children with more than one woman at the same time. I don’t remember seeing that kind of information in supplementary materials to date. From memory I can think of maybe two or three examples of agnate siblings published, but I doubt the archaeological age estimation (based on simple observation of skeletal remains) combined with radiocarbon age (usually given with broad CI) could be enough to prove a similar age of conception. Maybe a case of many siblings clearly of the same age and from many different mothers in the same burial could be a strong proof of this…

I recently read that theoretical models are actually trusted by no one except for the researchers who propose them, and experimental data are trusted by everyone except for the researchers who worked with them. I cannot agree more. However, we lack information about this question (as far as I know), so we may have to rely on indirect estimations, like the kind of models presented in the paper (or the one proposed for Post-Neolithic Y-chromosome bottlenecks).

The Late Proto-Indo-European word for bride comes from a root meaning ‘drive, lead’, hence literally ‘deportation’, so the bride was transferred from her father’s family to her husband’s house. Marriage was certainly an asymmetrical contract for its members, and the reconstructible word for ‘dowry’ further supports the weaker position of the wife in it. Also, ancient marriage could differ from a family agreement, because marriage by elopement, bride kidnapping or hostage was probably common (more or less socially regulated) for people belonging the same culture. Apart from this, I don’t know about reconstructed linguistic data pointing to polygyny, and I doubt archaeological data alone – without genetics – can help.

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:

Ancient DNA samples from Mesolithic Scandinavia show east-west genetic gradient

mesolithic-scandinavia

New pre-print article at BioRxiv, Genomics of Mesolithic Scandinavia reveal colonization routes and high-latitude adaptation, by Günther et al. (2017), from the Uppsala University (group led by Mattias Jakobsson).

Abstract (emphasis mine):

Scandinavia was one of the last geographic areas in Europe to become habitable for humans after the last glaciation. However, the origin(s) of the first colonizers and their migration routes remain unclear. We sequenced the genomes, up to 57x coverage, of seven hunter-gatherers excavated across Scandinavia and dated to 9,500-6,000 years before present. Surprisingly, among the Scandinavian Mesolithic individuals, the genetic data display an east-west genetic gradient that opposes the pattern seen in other parts of Mesolithic Europe. This result suggests that Scandinavia was initially colonized following two different routes: one from the south, the other from the northeast. The latter followed the ice-free Norwegian north Atlantic coast, along which novel and advanced pressure-blade stone-tool techniques may have spread. These two groups met and mixed in Scandinavia, creating a genetically diverse population, which shows patterns of genetic adaptation to high latitude environments. These adaptations include high frequencies of low pigmentation variants and a gene-region associated with physical performance, which shows strong continuity into modern-day northern Europeans. Finally, we were able to compute a 3D facial reconstruction of a Mesolithic woman from her high-coverage genome, giving a glimpse into an individual’s physical appearance in the Mesolithic.

Interesting is the genetic similarity found with Baltic hunter-gatherers from Zvejnieki:

To investigate the postglacial colonization of Scandinavia, we explored four hypothetical migration routes (primarily based on natural geography) linked to WHGs and EHGs, respectively (Supplementary Information 11); a) a migration of WHGs from the south, b) a migration of EHGs from the east across the Baltic Sea, c) a migration of EHGs from the east and along the north-Atlantic coast, d) a migration of EHGs from the east and south of the Baltic Sea, and combinations of these four migration routes.
(…)
The SHGs from northern and western Scandinavia show a distinct and significantly stronger affinity to the EHGs compared to the central and eastern SHGs (Fig. 1). Conversely, the SHGs from eastern and central Scandinavia were genetically more similar to WHGs compared to the northern and western SHGs (Fig. 1). Using a model-based approach (15, 16), the EHG genetic component of northern and western SHGs was estimated to 55% on average (43-67%) and significantly different (Wilcoxon test, p=0.014) from the average 35% (22-44%) in eastern and south-central SHGs. This average is similar to eastern Baltic hunter-gatherers from Latvia (28) (average 33%, Fig. 1A, Supplementary Information 6). These patterns of genetic affinity within SHGs are in direct contrast to the expectation based on geographic proximity with EHGs and WHGs and do not correlate with age of the sample.
(…)
Combining these isotopic results with the patterns of genetic variation, we suggest an initial colonization from the south, likely by WHGs. A second migration of people who were related to the EHGs – that brought the new pressure blade technique to Scandinavia and that utilized the rich Atlantic coastal marine resources –entered from the northeast moving southwards along the ice-free Atlantic coast where they encountered WHG groups. The admixture between the two colonizing groups created the observed pattern of a substantial EHG component in the northern and the western SHGs, contrary to the higher levels of WHG genetic component in eastern and central SHGs (Fig. 1, Supplementary Information 11).

From the same article, three samples with reported Y-DNA, the three of haplogroup I2 (one more specifically I2a1b). Regarding mtDNA, four samples U5a1 (two of them U5a1d), two samples U4a1, one U4a2.

Featured image: potential migration routes, taken from the supplementary material.

Related:

My European Family: The First 54,000 years, by Karin Bojs

steppe-expansion-corded-ware

I have recently read the book My European Family: The First 54,000 years (2015), by Karin Bojs, a known Swedish scientific journalist, former science editor of the Dagens Nyheter.

my-european-family
My European Family: The First 54,000 Years
It is written in a fresh, dynamic style, and contains general introductory knowledge to Genetics, Archaeology, and their relation to language, and is written in a time of great change (2015) for the disciplines involved.

The book is informed, it shows a balanced exercise between responsible science journalism and entertaining content, and it is at times nuanced, going beyond the limits of popular science books. It is not written for scholars, although you might learn – as I did – interesting details about researchers and institutions of the anthropological disciplines involved. It contains, for example, interviews with known academics, which she uses to share details about their personalities and careers, which give – in my opinion – a much needed context to some of their publications.

Since I am clearly biased against some of the findings and research papers which are nevertheless considered mainstream in the field (like the identification of haplogroup R1a with the Proto-Indo-European expansion, or the concept of steppe admixture), I asked my wife (who knew almost nothing about genetics, or Indo-European studies) to read it and write a summary, if she liked it. She did. So much, that I have convinced her to read The Horse, the Wheel, and Language: How Bronze-Age Riders from the Eurasian Steppes Shaped the Modern World (2007), by David Anthony.

Here is her summary of the book, translated from Spanish:

The book is divided in three main parts: The Hunters, The Farmers, and The Indo-Europeans, and each has in turn chapters which introduce and break down information in an entertaining way, mixing them with recounts of her interactions and personal genealogical quest.

Part one, The Hunters, offers intriguing accounts about the direct role music had in the development of the first civilizations, the first mtDNA analyses of dogs (Savolainen), and the discovery of the author’s Saami roots. Explanations about the first DNA studies and their value for archaeological studies are clear and comprehensible for any non-specialized reader. Interviews help give a close view of investigations, like that of Frederic Plassard’s in Les Combarelles cave.

Part two, The Farmers, begins with her travel to Cyprus, and arouses the interest of the reader with her description of the circular houses, her notes on the Basque language, the new papers and theories related to DNA analyses, the theory of the decision of cats to live with humans, the first beers, and the houses built over graves. Karin Bojs analyses the subgroup H1g1 of her grandmother Hilda, and how it belonged to the first migratory wave into Central Europe. This interest in her grandmother’s origins lead her to a conference in Pilsen about the first farmers in Europe, where she knows firsthand of the results of studies by János Jakucs, and studies of nuclear DNA. Later on she interviews Guido Brandt and Joachim Burguer, with whom she talks about haplogroups U, H, and J.

The chapter on Ötzi and the South Tyrol Museum of Archaeology (Bolzano) introduces the reader to the first prehistoric individual whose DNA was analysed, belonging to haplogroup G2a4, but also revealing other information on the Iceman, such as his lactose intolerance.

Part three, dealing with the origin of Indo-Europeans, begins with the difficulties that researchers have in locating the origin of horse domestication (which probably happened in western Kazakhstan, in the Russian steppe between the rivers Volga and Don). She mentions studies by David Anthony and on the Yamna culture, and its likely role in the diffusion of Proto-Indo-European. In an interview with Mallory in Belfast, she recalls the potential interest of far-right extremists in genetic studies (and early links of the Journal of Indo-European Studies to certain ideology), as well as controversial statements of Gimbutas, and her potentially biased vision as a refugee from communist Europe. During the interview, Mallory had a copy of the latest genetic paper sent to Nature Magazine by Haak et al., not yet published, for review, but he didn’t share it.

Then haplogroups R1a and R1b are introduced as the most common in Europe. She visits the Halle State Museum of Prehistory (where the Nebra sky disk is exhibited), and later Krakow, where she interviews Slawomir Kadrow, dealing with the potential creation of the Corded Ware culture from a mix of Funnelbeaker and Globular Amphorae cultures. New studies of ancient DNA samples, published in the meantime, are showing that admixture analyses between Yamna and Corded Ware correlate in about 75%.

In the following chapters there is a broad review of all studies published to date, as well as individuals studied in different parts of Europe, stressing the importance of ships for the expansion of R1b lineages (Hjortspring boat).

The concluding chapter is dedicated to vikings, and is used to demystify them as aggressive warmongers, sketching their relevance as founders of the Russian state.

To sum up, it is a highly documented book, written in a clear style, and is capable of awakening the reader’s interest in genetic and anthropological research. The author enthusiastically looks for new publications and information from researchers, but is at the same time critic with them, showing often her own personal reactions to new discoveries, all of which offers a complex personal dynamic often shared by the reader, engaged with her first-person account the full length of the book.

Mayte Batalla (July 2017)

DISCLAIMER: The author sent me a copy of the book (a translation into Spanish), so there is a potential conflict of interest in this review. She didn’t ask for a review, though, and it was my wife who did it.

Collapse of the European ice sheet caused chaos in northern and eastern Europe until about 8000 BC

deglaciation-europe-east

A new paper with open access has appeared in Quaternary Science Reviews, authored by Patton et al.: Deglaciation of the Eurasian ice sheet complex, which offers a new model investigating the retreat of this ice sheet and its many impacts.

According to the comments of professor Alun Hubbard, the paper’s second author and a leading glaciologist:

To place it in context, this is almost 10 times the current rates of ice lost from Greenland and Antarctica today. What’s fascinating is that not all Eurasian ice retreat was from surface melting alone. Its northern and western sectors across the Barents Sea, Norway and Britain terminated directly into the sea. They underwent rapid collapse through calving of vast armadas of icebergs and undercutting of the ice margin by warm ocean currents.

Some speculate that at some points during the European deglaciation, this river system had a discharge twice that of the Amazon today. Based on our latest reconstruction of this system, we have calculated that its catchment area was similar to that of the Mississippi. It was certainly the largest river system to have ever drained the Eurasian continent.

One thing that we show pretty well in this study is that our simulation is relevant to a range of different research disciplines, not only glaciology. It can even be useful for archaeologists who look at human migration routes, and are interested to see how the European environment developed over the last 20,000 years.

Interesting is its effect on population movements in eastern Europe, including the steppe, the forest-steppe, and the Forest Zone, during the Younger Dryas period and thereafter.

Another, recent build-up article on this model also by Patton and cols. of december 2016, in the same journal, is The build-up, configuration, and dynamical sensitivity of the Eurasian ice-sheet complex to Late Weichselian climatic and oceanic forcing. A summary is found at the University of Tromso website.

Discovered via News at Phys.org.

Featured image: Younger Dryas period, from the article.