The genomic history of the Iberian Peninsula over the past 8000 years

[Ruderico]

IIRC, he also models two samples with a lot more Sub-Saharan than any of the samples show with G25

Yes, there was heterogeneity amongst the medieval samples, but for ballpark figures it gets the job done. As said before heterogeneity suggests a recent influx, whereas homogeneity suggests no significant mixture happened recently, ie people just intermarried and got more and more similar as generations went by. By the way, you can also get similar values of "Guanche" in G25, but you need to use unscaled data rather than scaled. I tried that in late 2021 and curiously got the same figure they did in qpAdm:

[1] "distance%=0.6616"

         Iberia_Southeast_c.10-16CE

Iberia_IA,39
Roman_Colonial,35
Guanche,18.8
Germanic,7.2

So, does the North African and Arab influence vary by area or was it not constant? I say this because I compare it with the Arab conquest of North Africa where there was not much influence on the majority of the population but there was in certain areas

We know for certain there were regional differences, the reason we have lower levels today than in the past is because the source populations that contributed greatly towards our ancestry had less than these individuals from Al Andalus (aka north vs south), but we'd need multiple samples, from multiple sites, in order to assess its variability across Muslim Iberia (and Christian too, why not). Unfortunately we don't have such information so nothing can be said, we have to wait.

[fished]

I looked back at the supplemental material from the paper and it actually seems like the high SSA samples and some others aren't on the G25 datasheet, unless the IDs are different?

[jose luis]

What we do know from Bycroft's study, in addition to Olalde's, is that the former southern population had a very significant discontinuity, and that modern south Iberians are strongly/mostly descended from northern ones, likely the consequence of the repopulations during the Reconquista(1). Naturally the northerners had considerably less NA-related ancestry than the southerners during the middle ages, but to what degree no one knows. Alas there are a few theories, but since we have a total of 0 samples from Atlantic Iberia from the Roman period onwards this is all speculatory:

1- There were already differences across northern Iberia due to Roman colonisation, since Galicia and northern Portugal were more romanised than Cantabria for example.
2- It's also possible it's simply because the Reconquista advanced quicker in the West than elsewhere in Iberia - the border was south of the Lower Mondego by 878 - and that might have entailed the absorption of a population with closer genetic ties do southern Iberia (Mozarabs, who were rather important in the early Middle Ages and their influence was felt in architecture, for example), as well as a number of Berber individuals who had settled there. Since this all happened before religious differences became the main causus belli to justify Christian advance, the fact that some individuals were Muslim might have not had been as important as it would later be when the eastern border advanced south.
3- Spain had significant contribution from Basque individuals during the repopulations, according to Bycroft's study(2)(3). If this was the case, and considering Basques are a very unique population with virtually no NA-related ancestry, their contribution might have had the consequence of lowering this type of ancestry in Central and Eastern Spain. We can speculate a similar thing happened along the eastern coastline of Spain (initially Catalonia) with "French" individuals moving south and settling there, before their descendants moved south - this could also explain the Catalan language.


Naturally these aren't mutually exclusive, and could all have played a part in shaping regional differences within the peninsula.

Other facts that may have contributed to Portugal having more North African ancestors than the rest of the peninsula:
1) The climate of Portugal and Morocco is the same: Mediterranean-Atlantic. While Spain's climate is different, it is mostly Mediterranean-continental.
2) It was the Portuguese who made most of the conquests in Morocco (if the Spanish made any conquests there, it was much later). Then they brought slaves.

[Ruderico]

Other facts that may have contributed to Portugal having more North African ancestors than the rest of the peninsula:
1) The climate of Portugal and Morocco is the same: Mediterranean-Atlantic. While Spain's climate is different, it is mostly Mediterranean-continental.
2) It was the Portuguese who made most of the conquests in Morocco (if the Spanish made any conquests there, it was much later). Then they brought slaves.

Nr 1 is extremely dubious, at best there are similarities between southern Portugal and northern Morocco, but the Galician-Portuguese expansion came from further north/northwest where climate is clearly different. Besides there are ancient samples with around twice our levels of NA-related ancestry in southern Spain.
https://upload.wikimedia.org/wikiped..._of_Iberia.png
https://upload.wikimedia.org/wikiped...ca_present.svg


Nr 2 can't be the cause because the same thing is seen in Galicia, and to a slightly lesser degree in Asturias, León, Extremadura and Western Andalucia (western Spain)

[Jack Johnson]

Nr 1 is extremely dubious, at best there are similarities between southern Portugal and northern Morocco, but the Galician-Portuguese expansion came from further north/northwest where climate is clearly different. Besides there are ancient samples with around twice our levels of NA-related ancestry in southern Spain.
https://upload.wikimedia.org/wikiped..._of_Iberia.png
https://upload.wikimedia.org/wikiped...ca_present.svg


Nr 2 can't be the cause because the same thing is seen in Galicia, and to a slightly lesser degree in Asturias, León, Extremadura and Western Andalucia (western Spain)

Do you know what source population that Iberian heat map is based on? Is it Iberomaurusian/Taforalt or Morocco EN/LN?

[Granary]

What we do know from Bycroft's study, in addition to Olalde's, is that the former southern population had a very significant discontinuity, and that modern south Iberians are strongly/mostly descended from northern ones, likely the consequence of the repopulations during the Reconquista(1). Naturally the northerners had considerably less NA-related ancestry than the southerners during the middle ages, but to what degree no one knows. Alas there are a few theories, but since we have a total of 0 samples from Atlantic Iberia from the Roman period onwards this is all speculatory:

1- There were already differences across northern Iberia due to Roman colonisation, since Galicia and northern Portugal were more romanised than Cantabria for example.
2- It's also possible it's simply because the Reconquista advanced quicker in the West than elsewhere in Iberia - the border was south of the Lower Mondego by 878 - and that might have entailed the absorption of a population with closer genetic ties do southern Iberia (Mozarabs, who were rather important in the early Middle Ages and their influence was felt in architecture, for example), as well as a number of Berber individuals who had settled there. Since this all happened before religious differences became the main causus belli to justify Christian advance, the fact that some individuals were Muslim might have not had been as important as it would later be when the eastern border advanced south.
3- Spain had significant contribution from Basque individuals during the repopulations, according to Bycroft's study(2)(3). If this was the case, and considering Basques are a very unique population with virtually no NA-related ancestry, their contribution might have had the consequence of lowering this type of ancestry in Central and Eastern Spain. We can speculate a similar thing happened along the eastern coastline of Spain (initially Catalonia) with "French" individuals moving south and settling there, before their descendants moved south - this could also explain the Catalan language.


Naturally these aren't mutually exclusive, and could all have played a part in shaping regional differences within the peninsula.

It's also possible that there were fewer Berbers and Arabized North Africans in the Ebro valley, this could be related also to the fact Islamized Gothic nobilty lived in the region as well.
Also the expulsion and reshuffling or Moriscos might have ended up bringing some Southern Iberian converts to Galicia and not to Aragon which was administratively separated.

[RCO]

We can understand the Northern African presence in Portugal basically via Y-DNA E-M81 and mtDNA U6, they share more or less the same proportions in the general population, they are fragmented lineages from another bigger population (from North Africa) not originally native from Western Iberia, what is an indication they were massively incorporated in the North-Central phases of the Portuguese Reconquista, at least the biggest part of them. Moving frontiers are always incorporating people from the newly conquered lands, specially when they are intensively agricultural areas like estuaries, rivers and ancient established urban areas with ports and irrigated lands.

[Ruderico]

Do you know what source population that Iberian heat map is based on? Is it Iberomaurusian/Taforalt or Morocco EN/LN?

Neither, it says on top North Morocco. 10% Iberomaurissian in Iberia would be insanely high considering Moroccans should have ~30% or thereabouts.

[Ruderico]

Also the expulsion and reshuffling or Moriscos might have ended up bringing some Southern Iberian converts to Galicia and not to Aragon which was administratively separated.

I'm not aware of any significant number of Moriscos being forced into NW Spain, but perhaps someone with better knowledge on the topic could chime in.




Additionally Bycroft's study analysed the date of the admixture event and, for the Portuguese-Galician cluster, the average date was around 900AD give or take a few decades. It seems to be firmly early-medieval thought the peninsula, with the (partial) exception of the Portuguese-Andalucian cluster which seems slightly later. This cluster was also defined by an additional, albeit small, amount of SSA which could suggest and already admixed source like the 10-16th c. individuals we have seen in Olalde's paper.
There was an additional study that did this analysis and came to a similar date, but unfortunately I was careless enough to not save it on my computer and I have no idea who made it, nor how is it called.



Now whether the individuals involved in this main admixture event in the early MA were similar to those Roman/Visigothic Andalusians, or more uniquely north Africans (similar to contemporary Guanches) no one knows. I'm guessing both.

[jose luis]

Nr 1 is extremely dubious, at best there are similarities between southern Portugal and northern Morocco, but the Galician-Portuguese expansion came from further north/northwest where climate is clearly different. Besides there are ancient samples with around twice our levels of NA-related ancestry in southern Spain.
https://upload.wikimedia.org/wikiped..._of_Iberia.png
https://upload.wikimedia.org/wikiped...ca_present.svg


Nr 2 can't be the cause because the same thing is seen in Galicia, and to a slightly lesser degree in Asturias, León, Extremadura and Western Andalucia (western Spain)

1) I agree, to the north, temperatures go on dropping and the precipitation go on increasing, but there is a meteorological factor that unites Asturias, Galicia, Portugal, the Atlantic Coast of southern Spain and Atlantic Morocco, they are all regions under the influence of the cold current of the Canaries. A sea current can unite the climate of very distant regions. In Norway above the*Arctic Circle,*Røst has a climate bordering on*a subtype of the Mediterranean climate*due to abnormally warm temperatures despite its latitude located above 67°N latitude. Also, the Portuguese Institute of Climate (IPMA) gives another version of Köppen, for Portugal, and there are other similar classifications that give the same climate in general, for the Portuguese coast, which is where the majority of the population is.

https://www.google.com/search?q=clim...a2qSd0nJ2yVq8M
https://www.researchgate.net/figure/...fig1_250308832

2) I agree, the basic North African mix will be from the early middle ages, but its excess in Portugal and Galicia, in relation to Spain, must be from slaves. Galicia has always had close relations with Portugal which may explain this North African gradient towards Asturias.
----------------

The Portuguese border is different from the Portuguese language border. I think that, in this Bycroft study, the space between the two borders should have a color between the neighboring colors of Portugal and Spain.
https://pt.m.wikipedia.org/wiki/L%C3...esa_na_Espanha
An unimportant remark: It seems to me inappropriate to call the Bycroft study of Bycroft study. Bycroft has a secondary role in the study (well, not like the Galicians who played the freight boy).

As for the observation I made in another thread about hunter-gatherers, the expression of hunting instincts requires a cultural environment of its own, but people with these genes seem to be more difficult to scare, to be more indifferent.