I recently learned about a late Roman culture in the former province of Pannonia that survived Hun, Gepid, Slav and Avar incursions. This is the Keszthely culture. I can only summarize here what I read from Wikipedia articles about it.

The article on Keszthely culture says the name may derive from Latin castellum, "castle". The article on Keszthely city cites etymology from Slavic kostel, "church". However this word ultimately derives from Latin castellum. So they are both right. In the middle ages, churches were often fortified so the word came to mean church. The Keszthely culture, whose people were Romanized Pannonians, was Christian, contrasted against the first Slavs and Hungarian tribes that encountered them.

It is notable that these surviving late Roman settlements were located to the west of the Danube. Due to the geography, invaders into the Balkans generally went along the same major river routes, sacking the cities and villages along the way. As the barbarian incursions became more frequent toward the late Roman Empire, many townspeople decided to move off the main invasion corridors. This movement further crippled the Roman economy.

Fall of Pannonia

Many different groups raided, controlled or were settled in Pannonia during the late Roman Empire.

It appears that the region of Lake Balaton may have been lost to central Roman control as early as 433 if you look at this map of what the Huns controlled.

The Keszthely culture thrived during the Avar overlordship. The Keszthely culture page also mentions that they thrived under Gepid overlordship but when I look at this map of the maximum territorial extent of the Gepid kingdom I find that their western border was the Danube. So it looks like instead there were Lombards around Lake Balaton prior to the invasion of the Avars.

Anyway, things were going well for the Keszthely master gold artisans under Avar overlordship until they backed the wrong horse during an Avar civil war. Rather than copy the content from the Wikipedia article about this I suggest you just read the whole thing, it is very concise.

https://en.wikipedia.org/wiki/Keszthely_culture

As punishment the Avars destroyed the fortress of Fenékpuszta. Maybe this was a factor in the eventual demise of this culture.

Later a Slavic prince from further north, Pribina, was given permission by the Franks (who had defeated the Avars) to rule their former territory around Lake Balaton.

Pribina's main duty was to gather the groups of Slavs who were fleeing from various directions, and to keep them loyal to the Franks.

In 846 he built a new fortress just a few km SW of Fenékpuszta called Blatnograd. The article about him states that he Christianized the populace there. However if any of the Keszthely culture people were still around, they would have already been Christian. So maybe the Christianization refers mainly to Slavs and Avars.

How does the J-L283 come in?

Because an ancient sample from Mokrin, Serbia dating to 1900 BC was found positive for J-Z615 and because subsequent lineages have high diversity in the western Balkans, I believe that this lineage  became established in parts of Pannonia and Illyria in the Bronze Age. The vast majority of living J-L283 descend from this J-Z615 branch.

It is also possible that the J-L283 ancestor himself had originally migrated through this area though there is no hard evidence for it yet, instead so far we have higher diversity in Italy for the older J-Z600 lineages. We hope that additional testing of men in rare sibling J-YP91 will shed further light on the ancient origins / migration path of J-L283 to Europe.

Of all the groups that contributed to the ethnogenesis of the modern Hungarians, the ones that mostly, per capita within that group, ultimately trace back to ancestors who lived in Pannonia and Illyria during the Bronze Age would have been Romanized Pannonians.

Even if J-Z615 were not particularly numerous in Roman Pannonia compared to Illyria (perhaps due to losses suffered against invading Celts), due to proximity to Illyria we can expect some presence in Pannonia, as the Romans were always moving people around and sometimes they moved on their own accord.

The other groups (some listed above) could have assimilated some J-Z615 men but most of their male lines must ultimately trace back to areas not near the J-Z615 core geography of Pannonia and Illyria.

That being said, the man from the furthest east on this map appears to trace his male line to recently immigrated Slovaks from the Košice region of Slovakia.

We also have two men with surname Toth among our samples, the one who is J-Z1043>Y26712>Y29721 and the man whose SNP testing is in progress. I have been informed by Hungarian researchers that Toth means "Slovak" so could be indicative of Slovak origins. But neither man has close STR matches to indicate where his male line ancestors may have been living prior to his MDKA (most distant known ancestor).

The furthest west sample, from Pornóapáti, on the border of Austria, has a male line ancestor with a German name, Eberhardt.

On this map there are three lineages represented that appear to trace descent to the area of the Keszthely culture or somewhat near to it.

1. A man who is J-L283*
2. A man who is J-Z1043>Y26712>Y29721. His closest male line relatives are two lines, one from Rheinland-Pfalz, Germany and one from Silesia/Belarus/Ukraine. He only did a SNP test so far so we may have more to learn regarding his relationship to them if he does WGS/Big Y and YFull analysis.
3. One of two men who may represent their own subclade of J-Z1043, due to having rare alleles DYS392 = 12 and DYS385 = 13-18.

Ancient DNA from 6000 Keszthely Tombs Holds the Key

The clearest answer to whether or not any of these modern Hungarian male lines actually descend from members of the Keszthely culture can be found by genetically testing the remains of 6000 of their tombs.

Many countries prioritize research funding for ancient Roman sites, so maybe we can have hope that some of these remains will eventually be DNA tested.

J-L283 and J-Z631/J-Z1043 Research Fund

If you would like to support the research into our common origins, you can make a donation to me and indicate whether you want the money to be invested in a test to advance J-L283 origins or J-Z631/J-Z1043 origins. I will buy a test and YFull analysis at my discretion to advance the research into the respective group.

https://paypal.me/phylogeographer

I used to manage separate funds but they are discontinuing the Paypal money pool feature.

If you want to advance the research into a different specific lineage and are willing to pay for part or all of the test yourself, please contact me first before donating. I can see if someone is interested to test and whether they can pay for part of it.