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


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.


Heyd, Mallory, and Prescott were right about Bell Beakers


Sometimes it is fun to read certain “old” papers. I have recently re-read some important papers that predicted what we are seeing now in aDNA analysis with surprising accuracy:

Harrison & Heyd (2007): “We predict that future stable isotope and ancientDNA analyses of Beaker skeletal material will support our view that immigration played an important role in the Europe-wide Bell Beaker phenomenon”. – Duh, obvious, right? Wrong. Read the whole paper. It was already becoming a classic in the study of the Bell Beaker culture before the latest research on Bell Beaker aDNA, and it will be still more important from now on. There are different models for the Bell Beaker origin and expansion, and this was only one of them: we had the Dutch model, the radiocarbon date-based attempts to locate Bell Beakers in Iberia or North Africa,… I tried to highlight the best sentences from Heyd’s article to include them in my article, and I just couldn’t stop highlighting almost everything. It is surprising that 10 years ago Volker Heyd was predicting so much from such a limited amount of material, and with conflicting reports coming from everywhere, from palaeogenetics to radiocarbon dating. Not that today their chronology of Le Petit – Chasseur is accepted by all, but their general Bell Beaker and Yamna model has been clearly established as the most likely one with support from aDNA.

– Mallory in Celtic from the West 2 (2013), as the last of many to propose Bell Beaker as the vector of spread of Late Indo-European languages, but the first to relate it to North-West Indo-European: “The spread of Indo-European languages from Alpine Europe may have begun with the Beaker culture, presuming here a non-Iberian Beaker homeland (Rhineland, Central European) for that part of the Beaker phenomenon that was associated with an Indo-European language. While it is possible that IE language(s) spread with the Beaker phenomenon, it is questionable that this was associated with Proto-Celtic rather than earlier forms of Late Indo-European, at least part of which might be subsumed under the heading NW Indo-European. This is because the time depth of the dispersal of the Beakers is so great and the earliest attested Celtic languages are so similar (…)”. You might think that it is related to the Atlantic Indo-European theory favoured by Cunnliffe and Koch in the book… Wrong, he specifically dismisses a Neolithic spread of Indo-European, and a Calcholithic spread of Celtic languages as too early. You might also think that to publish that in 2013 has no merit, given the data. Wrong again. Just look at the trend among renown archaeologists – like Anthony (with Haak) and Kristiansen (with Allentoft) – trying to hop on the bandwagon of Corded Ware-driven Indo-European dispersal based on the “steppe admixture” proportion of recent genetic papers, and you realize he is going against the grain here.

Prescott and Walderhaug 1995 (as referred to in Prescott 2012): “The Bell Beaker period is the most, perhaps the only, reasonable candidate for the spread and final entrenchment of a common Indo-European language throughout Scandinavia (and not just Corded Ware core areas of southern and eastern Scandinavia), and particularly Norway”. Duh again? Not so fast. While Bell Beaker had been proposed before as a vector of Indo-European languages in Europe, the association with Germanic was far more controversial. Only the unifying Dagger Period was more clearly established as of Pre-Germanic nature, but it could be interpreted as of Corded Ware, Úněticean, or even early Neolithic origin, or a mix of them. Bell Beaker groups were never good candidates, if only because of the desire by some researchers to offer a romanticized (either more unifying or ancient) picture of a Germanic Northern Scandinavian homeland, explained as a culturally and genetically homogeneous group.

Their papers seem to state the obvious now that the latest aDNA samples are proving them correct, but it was far from clear years ago: remember the native European Basque-R1b – Uralic-N1c harmony disrupted by invasive Eurasian Indo-European-speaking warriors carrying R1a lineages from Yamna to Corded Ware? Well that is still a thing for some. And even today the most popular interpretation of the spread of Indo-European-speakers in Europe is based on the defined “steppe ancestry” proportion found in Corded Ware individuals, and a supposedly Yamna community formed by R1b-R1a lineages, which is obviously reminiscent of the identification of R1a lineages with Proto-Indo-Europeans based on the initial analysis of haplogroups in modern populations.

It is sad to imagine how much we would have improved in our knowledge, had we read their work with interest when it was necessary, and not now that we have most of the aDNA clues. Still sadder is to see people rely on genetic studies alone to derive today what are likely the wrong conclusions. Again.

I will end with a mea culpa. I hadn’t read those works; but even if I had, I would have stayed with the simpler, R1a-Corded Ware model of Indo-European dispersion. That oversimplification will remain in the different editions of our Grammar of Modern Indo-European as a permanent reminder. Simpler seems always better, and Cavalli-Sforza had famously asserted that ancient population movements could be solved with the study of the structure of modern populations. I think he was right, that we can in fact ascertain ancient population movements by studying modern populations if we include anthropological disciplines, but it is such a complex task – and geneticists have not shown a good grasp in (or interest for) Anthropology -, that it is nowadays clearly wrong to rely on modern population samples to derive conclusions about ancient populations, and we are better off studying ancient DNA samples in their context.

We were Back-to-the-Future-wrong, overestimating our potential in some aspects – like the results of researching modern DNA -, and underestimating it in others – like the potential changes that ancient DNA investigation could bring for anthropological disciplines. Just as we are wrong today in trusting the potential of admixture analysis to be self-explanatory, without a need for wide anthropological investigation (or even able to revolutionize archaeological and linguistic theories).

I hope to keep a more critical view of publications – especially the most popular ones – from now on.

How ‘difficult’ (using Esperantist terms) is an inflected language like Proto-Indo-European for Europeans?

For native speakers of most modern Romance languages (apart from some reminiscence of the neuter case), Nordic (Germanic) languages, English, Dutch, or Bulgarian, it is usually considered “difficult” to learn an inflected language like Latin, German or Russian: cases are a priori felt as too strange, too “archaic”, too ‘foreign’ to the own system of expressing ideas. However, for a common German, Baltic, Slavic, Greek speaker, or for non-IE speakers of Basque or Uralic languages (Finnish, Hungarian, Estonian), cases are the only way to express common concepts and ideas, and it was also the common way of expression for speakers of older versions of those very uninflected languages, like Old English, Old Norse or Classical Latin; and their speakers didn’t consider their languages “difficult” …

Therefore, to use different cases is the normal way to express concepts that non-inflected languages express in different ways – i.e. not “more easily”, but “differently”. That’s the point Esperantism has lost in its struggle to convince the world of its “easiness”. In fact, the idea that cases are difficult is so impregnated in Esperantism, that some did create “an old version” [probably deemed “more difficult”] of Esperanto called Arcaicam Esperantom, as a fiction of evolution from an older language…

Thus, among the European population (more than 700 million inhabitants), just around 200 million speak non-inflected languages, while the rest use at least 4 cases to express every possible concept. Within the current EU, more or less half of its speakers speak an inflected language – like German, Polish, Czech, Greek, Lithuanian, Slovenian, or non-IE Hungarian, Finnish, etc. – as their mother tongue.

For example, the literal sentence “I go to-the-house” [not exactly the common expression “I go home” which is expressed differently in each language] would be said in Spanish “voy a-la-casa”, or in French “je vais a-la-maison”, in Italian “vado a-la-casa”, etc. Therefore, in an “easy conlang” for Western European speakers, say in something called Esperanto, a sentence like “io vo a-lo-haus” is apparently “easy”, because the syntactical structure is similar to those non-inflected languages.

NOTE: In fact, there are other interesting concepts behind the use of the obligatory subject before the verb in languages like English or Esperanto, that appears usually in those languages that have reduced the verbal system; therefore, the subject is necessary only in those languages whose verbal inflection becomes too simple to express an idea that must still be expressed some way – more or less like different combinations of prepositions and articles are often needed to substitute the lost nominal inflection, as we discuss here. In those ‘less innovative’ languages that retain a rich verbal system, the subject appears for some reason, as e.g. in Spanish “yo voy a la casa”, which must be expressed differently in innovative languages, using different linguistic resources, like e.g. Eng. “I myself go to the house” (or maybe “it’s me who…“), or French “moi, je vais a la maison”. Is that obligatory subject and ‘simplified’ verbal system of Esperanto “easier”, and therefore “better”…? I guess not. It’s just an imitation of French or English that Mr. Zamenhoff deemed “better” for his creation to succeed, given the relevance of those languages (and its speakers’ acceptance) back in 1900…

On the other hand, in German it would be “Ich gehe nach-Haus-e”, in Latin, it is “vado ad-domu-m”; in Polish “idę do-dom-u” etc. The use of declensions, if compared to uninflected languages, is usually made of just a simple change of “preposition+article” -> “declension” – or, in the ‘worst’ case (as it is shown here), by a “preposition+article” -> “preposition+declension”.

To sum up, can some languages be considered “more difficult” than others? Yes, indeed. If seen from a European point of view, some linguistic features are not easy to learn: the Arab writing system, Chinese unending kanjis, Sino-Tibetan or Vietnamese tones, etc. can cause headaches to [adult] speakers willing to learn them… Also, from an English, French or Spanish point of view, learning a language like Esperanto might seem “better” because of its apparent and equivocal “easiness”… But, between (a) all Indo-European speakers learning a non-inflected language like English [or ‘easy’ Esperanto], or (b) all Indo-European speakers learning an inflected one like Proto-Indo-European?; I guess there is no language “easier” than other, and therefore the “better” option should come from other rational considerations, not just faith in the absurd ramblings of an illuminated Polish ophthalmologist.

Therefore, the question remains still the same: why on earth should any European willing to speak a common language select an invented one (from the thousand “super easy” ones available) than a natural one, like the ancestor of most of their mother tongues, Proto-Indo-European?