"Genetic Atlas" questions

[Mars]

I stumbled across this site, World ancestry/A genetic atlas etc http://admixturemap.paintmychromosomes.com/ I think you altready know it. Anyway, I took a look at their tutorials, they express both "simple event" admixture (one event some time in history) or multiple events of admixture. I checked the results, some appear strange to me. For example, for the spanish population, this atlas identifies two admixture events, one is very old, the other one occured between an african-like population (Bantu Kenya and moroccan) and a western european-like population (so called "french-like") around year 1334 CE, then recently, in the Middle Ages. What kind of event could have occured? Wasn't Spain already "reconquered" by christians in 1334 CE? How come the Bantu Kenya could be there? The greek population appears with one major admixture event in the Middle Ages, too, around 914 CE: a "polish-like" side mixed with a "cypriot-like" one. Is it a legacy of the Bulgarian Empire? Then, my own population, northern italian. One admixture event, occured around 66 BCE, between a "welsh-like" population and a "cypriot-like". I don't know what could have happened back then, Italy was under roman rule if I'm not wrong. Maybe the signal of a progressive admixture between central/southern colonist-farmers and the local gaulish population (welsh-like)?

 

[LeBrok]

Nice interactive map. Someone will need to decipher and educate the rest of us what they measure.

 

[Maciamo]

I am not sure how reliable is the Genetic Atlas. What is certain is that the dating of the admixtures can only be very rough approximations.

The Polish-like component in the Greeks probably corresponds to the 20% of so of R1a and I2a1 + some other Neolithic haplogroups. I don't think it all came in a single event though. The Goths would have brought some in the 4th century. Then the Slavs would have spread more "Polish-like" admixture to the Balkans, some which would have progressively entered Greece under the Ottoman rule. Peaceful migrations inside the borders of an empire are the hardest to record. Many aren't migrations as much as gradual population shift or homogenization through intermarriage with neighbours.

The Welsh-like admixture in the Northern Italians is obviously the Italo-Celtic ancestry, in other words all R1b-P312 in Italy, regardless of whether it came with the Italics or later with the Celts or Gauls. I don't think the Genetic Atlas can tell the difference.

 

[Drac II]

I stumbled across this site, World ancestry/A genetic atlas etc http://admixturemap.paintmychromosomes.com/ I think you altready know it. Anyway, I took a look at their tutorials, they express both "simple event" admixture (one event some time in history) or multiple events of admixture. I checked the results, some appear strange to me. For example, for the spanish population, this atlas identifies two admixture events, one is very old, the other one occured between an african-like population (Bantu Kenya and moroccan) and a western european-like population (so called "french-like") around year 1334 CE, then recently, in the Middle Ages. What kind of event could have occured? Wasn't Spain already "reconquered" by christians in 1334 CE? How come the Bantu Kenya could be there? The greek population appears with one major admixture event in the Middle Ages, too, around 914 CE: a "polish-like" side mixed with a "cypriot-like" one. Is it a legacy of the Bulgarian Empire? Then, my own population, northern italian. One admixture event, occured around 66 BCE, between a "welsh-like" population and a "cypriot-like". I don't know what could have happened back then, Italy was under roman rule if I'm not wrong. Maybe the signal of a progressive admixture between central/southern colonist-farmers and the local gaulish population (welsh-like)?

That study gives two events for Spain, and both are labelled "French-like" (one includes Norway, Morocco and Kenya.) The "Cypriot-like" event in Greece and North Italy include Middle Eastern (Syrian, Jordanian, Iranian) besides Cypriot and South-Italian input.

The admixture event dates seem to basically be "averages" of wider estimates. For the "French-like" side 1 of Spain these dates seem to be from around 1054 to 1586 AD, so it is not necessarily medieval. It could be from Early Modern times, but such dates hardly explain the East African input. It would be different if they had detected West African, as you could try to explain it by means of Spain's involvement in the slave trade.

The admixture events for the "Cypriot-like" side of North Italy are estimated as from about Etruscan and Roman times (766 BC to 550 AD), and the "Cypriot-like" one for Greece is estimated to be from early medieval times (718 - 1138 AD), which does not seem to fit very well with the "Iranian" input they found there.

 

[Mars]

One more doubt I have, I don't understand the reason why they don't find any admixture event in central and north/western european populations. In France and England, we had various population movements (celts, romans, and above all in England, germanic "invaders"): they're apparently not detected, IMHO. In Germany, there was a major movement eastward around 1000 CE, with population replacement and overlap in the area we could call "ex DDR". The Sorbs, an ancient western slavic community from Lusatia, are the living remnant of the former ethnic situation in eastern Germany; there's no track of this expansion in the Atlas, they have a very broad "GermanyAustria" sample which is a combination of a "Spanish-Ireland-North Italian" side and a "Finnish-Lithuanian-Orcadian" side, with no "strong evidence of admixture"...?

 

[Drac II]

One more doubt I have, I don't understand the reason why they don't find any admixture event in central and north/western european populations. In France and England, we had various population movements (celts, romans, and above all in England, germanic "invaders"): they're apparently not detected, IMHO. In Germany, there was a major movement eastward around 1000 CE, with population replacement and overlap in the area we could call "ex DDR". The Sorbs, an ancient western slavic community from Lusatia, are the living remnant of the former ethnic situation in eastern Germany; there's no track of this expansion in the Atlas, they have a very broad "GermanyAustria" sample which is a combination of a "Spanish-Ireland-North Italian" side and a "Finnish-Lithuanian-Orcadian" side, with no "strong evidence of admixture"...?

The results for France are labelled as "uncertain". In several places in central and northern Europe (Hungary, Poland, Scandinavia & the Baltic areas) they also found some admixture. Though I agree that it sounds rather arbitrary how they label the results. By the same token Germany/Austria and the British Isles should also be labelled as showing evidence of admixture.