What's crucial is that we have more of a fluent, smooth transition from one phase to the next, unlike it is in areas without a preceding Carpatho-Danubian cremation block tradition.
The most typical rite of the Proto-Thracians and later Dacians is the high prevalance of "invisible burials", due to some sort of deposition which left no archaeological traces, likely due to scattered ashes. And this tradition goes on from late Cotofeni groups, into Nyirseg and local Transylvanian groups, Tei, Verbicoara, Suciu de Sus, Wietenberg to some degree, but less, later Gáva, to some degree (less) Belegis II-Gáva, Vartop, Insula Banului and partly also Babadag (irregular burials oftentimes).
This trend goes somewhat down, with the Cimmerian intrusion and the disruption it caused, including early Channelled Ware, but we see a rise again in late Basarabi, but especially the Northern Basarabi and Gáva derivatives (Vekerzug Sanislau, Kustanovice, locals around Ciumbrud etc.), until culminating, once more, in the later Iron Age and historical Dacians.
Concerning what Zimnicea-Plovdiv-Cerkovna did, in the East Rhodopes, they introduced more advanced and widespread mining, a new form of subsistence (apparently kind of highland pastoralism, again something pretty typical for the Carpatho-Danubian core, since that's how already Cotofeni did survive the Yamnaya invasion) and a whole range of new bronze weapons and tools.
ZPC, with mining and highland pastoralism, did in fact occupy and exploit niches in the Rhodope region, which were barely used before at all. You can see, in the record, that a fairly advanced people came in, and did a planned colonisation. That's not some locals (which ones to begin with?!) which adopted a couple of symbols on their pots only - and even that would be an understatement, because very high end and complex patterns from Verbicoara-Wietenberg-Tei groups appeared in the East Rhodopes, which can barely be copied by locals out of nothing, yet alone what would be their motif to copy 1:1 such complex, and difficult to make patterns?
The whole scenery is dominated by this huge impact of a colonisation from the North. The only remotely similar scenario is when Gáva-related Channelled Ware groups came down, which, as we have established, likely meant that Thracian tribes met other Thracian/Daco-Thracian tribes. Which, by the way, was something earlier scholars sometimes argued for, that North Thracians/Dacians did influence South Thracians in the EIA.
Here a summary from a paper we discussed quite often, for the Turkish parts of the area in question:
In 1980, during the same Kırklareli survey campaign, a rescue excavation on a burial
mound took place. The site known as ‘Taşlıcabayır’ produced fifty-one fluted vessels
initially associated with the LBA, but later related to Troy VIIb2 and the Balkan EIA (see
Özdoğan 1987; 2001). It was part of a larger project that aimed to continue the work of
the 1930s, which had been encouraged by Ataturk himself, and to shed some light on
the archaeology of the Marmara region and the link between Anatolia and Europe.
Özdoğan noted that the results were quite different from those initially expected
(Özdoğan 2002: 284). Between 1980 and 1985 the Thracian parts of the project,
including the districts of Istanbul, Edirne, Kırklareli, Tekirdağ, Gelibolu and Ecebat, were
covered, resulting in the discovery of 300 prehistoric sites, 100 sites of later periods, 800
tumuli and 90 megalithic structures (Özdoğan 2001: 284). Study seasons took place
between 1989 and 1997 (see Özdoğan 1984; 1985; 1987; 1993; 1998). The results of this
project established that EBA settlements in European Turkey are few and small, part of
the Balkan pastoral communities, but also most probably in contact with Anatolia. There
was no settlement definitively dated in the 2nd millennium BC and new evidence was
registered only from the end of it, the transition between the LBA and the EIA, which
Özdoğan interpreted as belonging to a migration from Southeast Romania, which
brought with it the tumuli as well as the dolmen structures (Özdoğan 2001: 287).
In the Eastern Rhodopes and Sakar by contrast, pastoral groups colonised a
specific mountain ecotone following ridge landforms with potential for regular access
to grazing lands and running water. This micro-region was perhaps also attractive for its
natural mineral resources as suggested by the gold ore exploitation at Ada Tepe. The
only evidence for the burial rite practiced here are the dolmen structures with preserved
LBA pottery. The typical ceramic material is richly decorated incised ware, partially
overlapping with types distributed in the Upper Thracian Plain. Correspondence with
some of these pottery types can be seen in some ceramic traditions documented north
of the Danube, precisely in the Carpathian Basin and the Hungarian Plain, which is
potentially indicative of the origin of the incised ware in Thrace. In the western part of
the Rhodopes, possible nomadic or semi-nomadic groups brought cremation in tumuli
to the area and left little or no trace of permanent habitation.
In the LBA, in groups like Suciu de Sus, Lapus, but to some degree also ZPC, we find kind of more monumental sites, which however contain quite often no regular burials! This too, beside the whole ceramic, subsistence pattern, tools and techniques etc., etc. connect the Carpathian basin/Carpatho-Danubian block with the South Thracian groups and ZPC into early Fluted/Channelled Ware into Psenichevo as well.
The West Rhodopes were settled by groups from Brnjica (related to Vatin, Paracin and Belegis):
The pottery assemblage typical for this area partially overlaps with the types distributed in the
Eastern Rhodopes, but it is much closer to the ceramic tradition of the Brnjica culture.
Probably communities from the Brnjica culture also populated the middle Struma Valley,
forming a system of defensive settlements towards the end of the 13th century BC.
Like I said some months ago, the choice is ONLY between Verbicoara-Tei-Wietenberg/ZPC and Gáva-related Channelled Ware, all other groups were eventually eaten up.
A second spread can be connected with the groups of the Verbicoara and Tei in
Romania. An indication of population movement can be traced through northwest and
central Bulgaria towards the Upper Thracian Plain and the East Rhodopes. The short life
of the sites in northwest and central Bulgaria can be explained by the temporary
character of the common cave sites, such as Devetashka, Tabashka, Emenenska and
Muselievo, (Bonev 2003: 32), which were probably those sites that survived due to
better preservation. It seems possible that there are two separate periods within the
Thracian LBA linked to separate pottery traditions originating in the areas north of the
Danube. The earlier period, associated with the 16th and 15th centuries BC, was based
on the Verbicoara and Tei traditions, but developed its own character in Upper Thrace
and the East Rhodopes. Later connections are associated with the cave settlements in
central-north and northwest Bulgaria and with the Govora group, which also originated
north of the Danube River. Some of the LBA traditions in west Thrace and Thasos, could
have been related to either of these distributions or, in a more direct connection, with
the East Rhodopes. A large portion of the material culture in this area, however, seems
to have ‘arrived’ through the mechanism of the appearance of the Macedonian incised
ware. This combination of material culture gives the specific character of the west
Thracian sub-region (Figure 10.9 d). With respect to Macedonia per se, there are
substantial differences with the material from earlier phases. The roots of the
appearance of the incised ware in this area can be seen in Wietenberg and Monteoru.
The scenario of Verbicoara-Tei-Wietenberg vs. Gáva-related is no strict one, because we might in this case deal with some assimilation process indeed. That has the following reasons:
- When Gáva-related Channelled Ware spread, they met closely related people which split from them just a couple of generations ago. That kind of relationship makes any sort of cultural diffusion way more likely, than e.g. ZPC/Gáva vs. Illyrian, Mycenaean, Brygi and Paeonian groups.
- Also, when Gáva-related Channelled Ware unified the Daco-Thracian world, there was quite some population density in areas like the East Rhodopes. When Tei-Verbicoara-Wietenberg moved South, these areas were practically uninhabited. When the Gáva colonisers and warbands came, they met larger numbers of locals, which were specialised highlanders in some areas as well.
The most important point is, that whatever Psenichevo used, it came from the Carpatho-Danubian sphere with additions from the steppe (first Noua-Coslogeni, later Thraco-Cimmerian, finally Scythian). The Southern Greek/Aegean influence started to gain importance soon after the LBA-EIA, but that was too late for the main expansion and spread of both E-V13 and Daco-Thracians. This could only have caused a more Hellenised later culture and Aegean-Anatolian admixture, which the South Thracians likely acquired.
Funnily, some elements of say Psenichevo are more like what we find in LBA Transylvania, than what Gáva/post-Gáva produced. This is because Gáva was quite a shift there, while in the South, it looks like older Carpathian traditions survived in areas like the East Rhodopes, and kind of re-emerged, on top of Gáva-style, with additions from Encrusted Pottery, Aegean-Anatolian customs and the steppe.
But to imagine Psenichevo without the Carpathian roots is absurd. It was much more similar to the Carpathian traditions than to the Aegean-Anatolian ones. And locals are none of importance pre-ZPC.