Surprises in the tea leaves? Sounds like new data ahead...maybe... "Siret's Smile" is discussed at Bernard's Blog.
And a little disclosure. I've read the four sentences in the abstract and the references. Hopefully a nice person will send me a copy of the paper!
The best I understand is that Gustav Kossinna and Louis Siret represent different flavors of a diffusionist archaeological interpretation. From this viewpoint, innovation occurs rarely in humanity and when it does, like the invention of the airplane or the use of metals, it originates from an epi-center, a homeland, and by some process spreads to other places, sometimes dragging an entire cultural package with it.
Diffusion is demonstrably more often the lazy act of borrowing, but it can also be a full-blown, heads-spinning-off-shoulders population replacement in the other extreme. Major disruptions in the archaeological record, according to the diffusionist perspective, are not evidence of a kind of localized punctuated equilibrium, they are instead actual disruptions from an external source.
Kossinna viewed culture as necessarily rooted in ethnicity and equated changes in material culture with changes in ethnicity, whereas Siret viewed religion and technology as the glue that bound most cultures together, however routinely stimulated from the outside. "Kossinna's Smile" was published as a prelude to, and with foreknowledge of, The Bell Beaker
Phenomenon and the Genomic Transformation of Northwestern Europe. From that study we learned that the heads-spinning-off-the-shoulders variety was the primary instigator for material change in the Island of Britain.
Importantly, Volker Heyd sees the original, external stimulation of proto-Beaker Culture in Iberia as potentially having subtle steppic tendencies. That's probably a minority view, but he gives examples of this in his paper. In other words, I doubt he would he would accept that the northern and southern Beaker domains had totally discrete origins that were simultaneously and coincidentally expanding on each other and somehow melded into pan-Beaker through acculturation.
"Siret's Smile" by Guilaine is a reply to Heyd's "Kossinna's Smile" which may be nothing more than an argument for what embodies the Beaker Culture center of gravity. This question is dealt with by David Reich in the video presentation linked by Bernard, and Reich clearly sees religion as the glue of Beaker material culture in opposition to the ethnically monolithic Corded Ware.
Guilaine appears to be of an opinion similar to Oliver Lermercier, Convertini, Besse & co. in the idea of a Greek Implantation Model of the Beakerization of SW Europe. It's a diffusionist view also, which emphasizes the evangelization of local people by elites. It may be entirely valid for this region. But I doubt he's arguing acculturation, and looking at the abstract, it seems that Guilaine's argument and style (Siret's Smile) is hinting (or taunting) at even newer evidence not disclosed, maybe genetic.
Although Siret's chronology for Southern Iberia is technically outdated, in broad terms he saw the beginning of the Metal Age in Southern Iberia as being stimulated from the Eastern Mediterranean, which he called "Phoenician". These were colonies of skilled men devoted to mining and trade with high status who upgraded the local culture. Then in the regular Bronze Age, Iberia went through the process of "Celticization", as he called it. (Aranda Jimenez, 2015, pg8) Which brings us to the tea leaves...
At 1:53 in the video Bernard linked, David Reich specifically says that there was almost "no shared ancestry between the Spanish practitioners of this culture..and the Central European ones...". But let's look at that statement closely. According to Siret's view (Guilaine), that's kind of irrelevant since most Spanish practitioners of this culture are native Spanish who have become indoctrinated in a new religion. And Guilaine, at least from the snippets I viewed, emphasizes the role of the Eastern Mediterranean elites (Siret) in remaking early Metal Age Spain.
Of course, during the Bronze Age Spain is increasingly Steppified (Celtified), and later, actually Celtified.
So of course Guilaine presents new archaeological data in this paper to counter Heyd. I haven't seen it yet, but when I do, I'll post part 2. I imagine that it's new data from Valencia de Conception which will be rather conclusive, like isotopes or updated radiocarbon dates. I may be reading too much into this, but I imagine ancient DNA (not disclosed in this paper) maybe be lurking around the corner to offer a new twist to the narrative. Maybe not.
Recent palaeogenomic data have expanded the debate concerning the
direction of cultural transmission during the European Chalcolithic by
suggesting the western movement of people from the Eurasian Steppe. Heyd
(2017) considers a simultaneous spread of material culture as
supportive of these model. The author addresses Heyd’s suggestions in
the light of new archaeological data from the southern Iberian
Peninsula. These data strongly suggest both Eastern Mediterranean and
endogenous influences and innovation in the spread of culture across
Europe during the third millennium BC.