Thank you very much for your detailed answer , for a noob about genetics .
However , I think you are wrong making the hole thing Dacian centric .
Historically , the Dacians were a late development , long after Thracians and Getae were mentioned . Archelogically , they appear to be the result of a limited Getae migration north of Danube and a cultural mix of Balkan people with Celtic and Agathyrsi elements . But all this happened not earlier than 3-2 century BC .
That's why I write about North Thracian/Dacian quite often. You see, North Thracians, which formed the main body of the Daco-Thracian people, where multiple, closely related groups which emerged, just like the South Thracians, from the spread of Carpatho-Danubian cremating people, unified in the LBA by the Gáva-related Channelled Ware and later in the Southern block (which encompassed much of Serbia and Southern Romania) Stamped Pottery. Now who exactly was the central group among these North Thracians to create the later Dacian sphere, is up to debate, but they were in any case closely related and interconnected ever since the LBA.
You might want to study Padea-Panajurski Phenomenon , about the trans-Danubian culture as a posible root of the Dacian people . More, is posible that Dacians were only a ruling military class , not a ethnicity or people . See how fast "Dacian" culture and religion dissapears after Roman conquest .
In fact, I think it was a combination, because we see in the archaeological records that these were all closely related, interconnected (North) Thracian/Daco-Thracian people. The Dacian rule is similar to the earlier Gáva-related Channelled Ware: It might to a large degree being an unification process under La Tene, steppe and South Balkan/Greek influences.
Like we have Dacian-related/North Thracian groups in areas like Transylvania (Ciumbrud group locals/neighbours), Upper Tisza (Sanislau group), Transcarpathia (Kustanovice), South Western Romania (Ferigile, Late Basarabi), Getae at the mouth of the Danube etc. What we see, to repeat it again, with the Dacians is not necessarily the expansion of new people from place X, but rather emergence of a new type of ruling class which seems to have unified all these groups under one rule and new codex.
This is particularly noteworthy since some of the elements later seen in Dacians came clearly from the Western La Tene contact zone and groups to the North, while others and the final form are rather coming from more Southern (not South Thracian though) regions with phenomenons like the Padea-Panagjurski Kolonii phenomenon. This was just yet another unification process, like the one which happened with Gáva-related Channelled Ware, when the Thracian Hallstatt sphere was created.
And in a similar way we can see areas which incorporated people already connected and related before (already Dacian, related North Thracian tribes) and then, also, the expansion of these unified horizon into foreign territories (like Celtic La Tene areas).
I don't think you have genetic evidence to claim Dacians as a proto root of the E-V13 people from Urnfield culture . I think you follow the conventions of the 19th century in the naming of the Daco-Thracians or Geto-Dacians .
I understand that genetics prove the migration of a E-V13 people from Urnfield space into the Carpathian and Balkan space . This does not make any of them Dacians . But following the trail , we found this people in the Southern Balkans , named Thracians by the Greeks .
That Thracians in the South are an integral part of these Daco-Thracian group of people, but they are just a subset of it. That's the crucial takeaway.
We discover that they are genetically similar to the original E-V13 people that started this migration .
Is naming the Northern (of Danube) Thracians as Dacians , just a convention , because it does not stand the historical facts ?
Question is , how many samples of Dacians are analized , from what period and what locations ? How do they compare genetically to the original E-V13 people or the Southern Thracians ?
Since we should get, hopefully, both EBA-MBA samples from Transylvania and Early to Middle Iron Age samples from the same region (Ciumbrud "Scythian" group) and La Tene era locals, we can compare them and look whether they are the same or not, and if not, in which way they differ. Like are many of the Ciumbrud locals more Balkan-like, probably because they are from Basarabi rather than Gáva?
Also I undersatand that Agathyrsi were the original people in the Carpathian space , not the Dacians or Northern Thracians, which were migrators into the region .
That's wrong, because the region was inhabited by Gáva, Gáva-Kyjatice mixed people and Basarabi people before, and these are all North Thracian/Daco-Thracian groups. The Scythians were similar to the Yamnaya, the Cimmerians or later the Sarmatians just foreign newcomers from the steppe, which couldn't replace the locals.
We see that the best in the Ciumbrud group samples, which, even though they are from a central "Scythian" cemetary, completely surrounded by cremation burials from local North Thracians/Dacians, was highly mixed and showed the local element.
Therefore if even this "most Scythian" group was so much local and North Thracian/Dacian, what do you think the neighbouring groups will be? And we already know it from the Chotin Vekerzug Balkan-like group, which had an E-V13 already, that they were Balkan-like and had E-V13.
Therefore the Agathyrsi themselves were a Thraco-Scythian/Daco-Scythian mixed people and were later replaced by completley North Thracian/Dacian people. This is no speculation, because that's what the abstract clearly stated. La Tene era samples from a local group were completely local Carpatho-Balkan, with practically no Northern Central, South Balkan or Scythian admixture any more, which proves that this local element always persisted. It appears in the Scythian mix and then replaces this Scythian mix. This is as straightforward as it can be.
Were the Agathyrsi Indo_Europeans , or what were they ? Which people of Balkan-Carpathian space were Indo-Europeans genetically ?
Like described above, the Agathyrsi was Thracians with a small influx of actual Scythians and South Balkan newcomers, which influenced the wider Daco-Thracian population of the region. Like in the Sanislau group to the North West of Ciumbrud, the actual Scythian influence was near zero genetically as we can see, but culturally they caused a shift. Same with the La Tene Celts btw.
As for the core region of E-V13 in Romania , this is most probably an influence of south of Danube people , a Vlach migration during the Second Bulgarian Empire or later . As you can see , the area is very close to Danube , a narrow strip , which was deserted at the time of Slavic settlement north of Danube . So there is no much continuity of E-V13 in Romania , after the Roman retreat at 271 AD.
Still , wanna be Dacian roots in Romanians are very low , not as nationalistic propaganda wants us to believe .
The issue is that the very late Roman population in the Danubian provinces was primarily Dacian derived shortly before the migration period. We do know this because the records make clear that the earlier population was largely erradicated, the region depopulated, and Daco-Romans and Dacian tribals were the primary source for the resettlement.
I quoted in various threads here and elsewhere the ancient comentators, which made this absolutely clear. To rename the provinces of Dacia ripensis and Dacia mediterranea was not a simple change of the label, it reflected a true shift due to the earlier depopulation and resettlement of the region, primarily from Dacian-derived people.
Also worth to note: Even in modern Bulgarians a large fraction of the E-V13 presence is likely due to Dacians moving in, in the late period. A good indicator for North vs. South Thracian proportions is the relative frequency of E-Z5018 vs. E-V13 as a whole.
There are branches of E-Z5018 which could be Southern in origin, and there are many non-Z5018 Northern branches. HOWEVER, the bulk of Z5018 is Northern and therefore the relative proportions of Z5018 and secondary the central group Z5017 give us a hint as to how Southern/Northern E-V13 in a population is.
E.g.: Bulgaria has 38 : 123 vs. Russia has 47 : 122 at FTDNA. Now the numbers for E-Z5018 would be higher, if all FTDNA testers would have made a more downstream test, but this already shows a significant difference. The Mediterranean area and Bulgaria have a higher frequency of non-Z5018/Southern branches vs. most of the continental areas. The exceptional instances are all related to later Dacian migrations to the Central and Southern Balkans, which however led to now Imperial Roman spread on the same level any more, because at that time the Roman Empire was already breaking apart.
Looking at this, we can say that areas like Bulgaria have a higher presence of South Thracian survivors, but still a large fraction is derived from later North Thracian/Dacian people, which however did inhabit the Northern Bulgarian zone from the start anyway.
Another take on this problem is the relative frequency of two main Northern branches of E-V13 under Z5018, namely E-L241 and E-FGC11457. If using a threshold of 15 %, a clear pattern emerges which shows where the South Thracian and early Roman mediated spread was more common, contrary to the red areas where a continental spread of Dacian-related lineages was more influential and happened e.g. in Albania-Greece fairly late. This late Dacian-related expansion of E-V13 in the Balkans created a wedge on the map, between the core Roman Imperial areas.
And we will see, once we get more Roman era samples, when exactly much of the E-V13, especially the Northern branches, arrived. My prediction is they came fairly late, a large fraction only with the resettlement in the Late Roman era and the migration period.
