The European Early Bronze Age (EEBA), although difficult to define for all cultures involved, may be said to have begun with changes in settlement systems, burial customs and material culture, in particular the mostly plain pottery. This process began ca. 2500 BC in the entire Carpathian Basin, Italy, and to the east, with a general decrease in decoration on pottery: Vessels are no longer messengers or symbols indicating an affiliation to an identity group; their functional aspect is emphasised. Begleitkeramik are common starting with the Classical Bell Beaker, including jugs, cups, and bowls, low and deep (Heyd 2013).
This innovation process progresses gradually ca. 2400–2250 BC in a wide area from the Lower Danube down to the Alps and northern Italy, and is recognised in the Carpathian Basin by a return to tell settlements as a development from south to north, affecting Vinkovci, then reaching the Danube, and finally early Nagyrév ca. 2250–2000 BC. Exotic objects that would later become iconic of the Bronze Age begin to appear (Heyd 2013). Continuous use or emergence of circular enclosures in central Europe, appearing (or being essentially improved) after ca. 2500 BC in northern Germany, Iberia, the British Isles, or Bulgaria, suggest a renewed Europe-wide concept of sanctuary, and extensive communication networks with intellectual and religious contents circulating alongside raw materials (Spatzier and Bertemes 2018).
The regional organisation changes thus from trans-regional cultural phenomena prevalent ca. 2750–2500 BC, like Vučedol and Makó/Kosihý–Čaka, to a cultural fragmentation after ca. 2400 BC with 5 new regional units, apart from the continuing late Makó/Kosihý–Čaka, late Somogyvár–Nagýrev, Nyírség, Gyula-Roşia, Maros (Pitvaros), Ada, Gornea-Orleşt. Distinguished by a significant degree of similarity of material culture (burial ritual and pottery), they seem to be a sign of the birth of chiefdoms and tribal organisation (Heyd 2013).
This combination of graves with Bronze Age equipment, cultural fragmentation and tell resettling and expansion gradually expands in importance and consistency, from 2300 BC and especially 2200 BC onwards. This influence is appreciated rather soon in neighbouring cultures, such as the exotic objects appearing in the early/mid–23rd century BC in the Csepel group of the Bell Beaker culture, like a copper/bronze halberd and roll-headed pins or Noppenringe (Heyd 2013).
After the expansion of the Classical Bell Beakers ca. 2500 BC, the Middle and Lower Danube (up to central Germany) and Moravia turn into the cradle of the new Early Bronze Age Civilisation. This expansion and subsequent connected cultural developments are responsible for the creation of extensive sociocultural contacts that will last, with certain evolutionary changes, the whole European Bronze Age. Communities tend to concentrate along interregional trade routes, and long-range exchange becomes common, supporting the unifying, true pan-European nature of the Bell Beaker people, later intensified by certain regional centres (usually in central Europe) throughout the Bronze and Iron Ages (Heyd 2013).
Significant waves of regional fragmentation and emancipation from previous traditions are also seen over the 23rd century BC in Bell Beaker territories in the vicinity of the Carpathian Basin, such as Oggau-Wipfing in the Middle Danube, Proto-Únětice in the Moravian province, or Chłopice–Veselé in Lesser Poland. Apart from the fragmentation, the first centralisation waves appear with the first fortifications on hills in southern areas, and longhouses predominate as living places and foci of the new settlement planning (Heyd 2013).
After ca. 2200 BC, a gradual and continuous process involving the intensification of cultural subsystems is seen, and then massively in the 21st century BC. Metallurgy increases in regional centres. Eventually, the next stage of a full-fledged “European Bronze Age package” is reached from ca. 2000 BC on, when wide parts of temperate Europe develop a system of intensified exchange where trade becomes established, based on a hierarchically organised society, with many prestige and status objects belonging to the elites, culminating in their lavishly equipped graves (e.g. Leubingen and Helmsdorf in Germany, Łęki Małe in Poland, Thun-Renzenbühl in Switzerland, Kermonen en Plouvorn and Saint Adrien in Brittany, and Bush and Clandon in Wessex), and large metal hoards. There are also precious metal vessels, economic specialisation, specialised craft production, and widely available tin–bronze (Heyd 2013).
EBA groups emerge therefore within a unifying framework established previously by expanding East Bell Beakers, which shows thus common cross-regional features, such as shared object forms, burial rites, and new technologies, like the introduction of tin–bronze, and the advent of complex metalworking techniques. All groups are connected from west to east, from north to south Europe, through farming communities that show the emergence of a leading social group of chieftains, characterised by rich single graves with votive depositions, as well as hoards with new kinds of ceremonial weapons, such as solid-hilted daggers (Vollgriffdolche) and halberds (Heyd 2013).
The Early European Bronze Age region becomes finally divided into three fundamentally distinct provinces of cultural material and burial rituals, which act as cultural centres that influence adjacent regions. Three supra-regional culture complexes formed by different groups appear between the Rhine in the West and Transdanubia in the east, the Alps to the south, and the line between Mittelelbe–Saale-region to Upper Silesia/Lesser Poland: its common basis is built by the East Bell Beaker group and regional European groups. Mainly along the Danube appears the Danube Early Bronze Age culture; to the north appears the Únětice complex, forming separated regional Únětice cultures; and the Eastern Early Bronze Age is formed by the Nitra, Mierzanowice and Košťany groups, to the north of the Danube and to the east of the Morava in East Moravia, in south-west Slovakia and Lesser Poland, including (with Košťany) the northern Carpathian Basin (Heyd 2013).
These central groups are delimited from Western Early Bronze Age cultures (Adlerberg and Rhône, based on the West Bell Beaker groups), from Carpathian cultures (Makó/Kosihý–Čaka, Somogyvár–Vinkovci, and Vučedol), and from other northern traditions based on Bell Beaker cultures – like the Veluwe-type Beakers from the Netherlands and the Rhein – or Corded Ware – like Riesenbecher, apart from the developing Nordic Dagger period to the north. Lower Danube, Únětice, and Nordic BA, strongly unified in that they are saturated with huge amounts of diverse metal goods. This is interpreted as a response to a great demand for prestige objects by local communities, and indirect indication of their social differentiation and ranking, as part of the materialisation process of the transformation in ideology (Kadrow 1998).
During the evolution of this Early Bronze period, different shifting independent (“pan-European”) centres of cultural and technological innovations can be seen in Central Europe, from the Upper Danube ca. 2200–2050 BC; to the northern ranges of Únětice ca. 2050–1900 BC; to the Bohemia and Moravian regions ca. 1900–1750 BC; and later, ca. 1750–1400 BC, to one centre in the north-eastern part of the Carpathian Basin (a complex of Füzesabony, Mad’arovce, and Věteřov cultures), in contact with the Aegean world, and another represented by the circle of Nordic cultures, with a singular culture. A different European centre, heir of an important Corded Ware culture influence on Bell Beakers, developed early (at least ca. 2300 BC) as the Epi-Corded Carpathian Cultural Circle, which manifested itself in the Mierzanowice culture (Kadrow 1998).
The real transformational change in Bell Beakers, shifting from a unifying expanding culture to the different regionalisation trends, starts when the centre of gravity shifts from expanding Bell Beakers ca. 2500/2400 BC to the real trade boosted by Aegean influence ca. 2300/2200 BC. The intermediate period sees both worlds meeting in their respective expansions, e.g. in the Adriatic, in the Carpathian Basin, and possibly even in Iberia (Heyd 2013).
Yamna admixed with local EEF-like populations from Hungary before (and during) their evolution into Classical or East Bell Beakers. During their explosive expansion, tens of thousands of Yamna/East Bell Beaker migrants also admixed with local European populations through exogamy, revealing multiple male-biased migration waves, based on the prevalent Yamna R1b1a1b1-L23 (especially R1b1a1b1a1a-L151) lineages and the reported replacements of male lines in all European territories where it spread, in some cases—like the British Isles or Iberia—close to 100%, while the spread of Steppe ancestry was in many cases inferior to 50% and usually decreasing with distance (Olalde, Brace, et al. 2018). Nevertheless, a reported early Bell Beaker sample from France, likely from the Eastern Swiss–Alsatian–Southwestern German province, shows elevated Steppe ancestry and clusters quite close to Yamna (Brunel 2018), showing that the Yamna-like cluster was still prevalent among expanding East Bell Beakers ca. 2500 BC.
The admixture of non-Iberian Bell Beakers relative to Yamna samples has been described as mainly with EEF populations with hunter-gatherer ancestry closer to Körös (in a La Braña–Körös WHG cline), higher than the one found in samples from Hungary LCA or Germany MN. The admixture in Iberian Bell Beakers shows a better fit with previous Iberian populations (from the Neolithic or Chalcolithic), except for Copper Age populations from the north, which harbour more hunter-gatherer ancestry. Similarly, early samples from the British Isles show high variability in ancestry compatible with recent admixture, like the Boscombe Bowmen collective burial, where two closely related individuals (ca. 2500-2140 BC), likely third-degree relatives, share ca. 13–43% ancestry and show the lowest and one of the highest amounts of Steppe-related ancestry, respectively (Olalde, Brace, et al. 2018).
The reported Steppe ancestry in Bell Beaker samples is higher instead of lower in some later samples from central, central-east, and northern European territories, and in the British Isles (Olalde, Brace, et al. 2018). Similar to the increase in Iberian farmer contribution found exclusively in Bell Beakers from Iberia, this increase in Steppe ancestry in certain late Bell Beaker groups compared to earlier ones from nearby regions may be explained by exogamy, more specifically admixture with females of local Corded Ware peoples, who are the best fit for that increased ancestral component from the steppe. So for example, Bell Beakers from the Netherlands (and consequently the British Isles, see §viii.5. Pre-Celts) show contribution of ancestry typically found among the Single Grave individuals they replaced. Certain early Yamna pioneer groups may have in turn increased this Steppe ancestry among some Corded Ware groups from central Europe, prior to the arrival of Bell Beakers (see §vii.1. Western and Eastern Uralians).
Unlike the admixture of peoples of Yamna descent with EEF populations found in Bell Beakers, where typical Early European farmer mtDNA subclades are found together with typical Yamna Y-DNA lineages (Olalde, Brace, et al. 2018), it is difficult to pinpoint precise mtDNA subclades in Bell Beakers corresponding to their admixture with Corded Ware peoples, because of the shared mtDNA originally from the Pontic–Caspian steppes, and because of the previous admixture of central European Corded Ware peoples with EEF populations, too (Juras et al. 2018), similar to Yamna groups from Hungary (see §vii.7. North-West Indo-Europeans).
Main R1b1a1b1a1a-L151 subclades expanding with East Bell Beakers are R1b1a1b1a1a1-U106/S21/M405 (TMRCA ca. 2700 BC) and R1b1a1b1a1a2-P312/S116 (TMRCA ca. 2500 BC), with a comparatively earlier successful expansion of the former’s surviving subclades. The earliest R1b1a1b1a1a1-U106 subclades are found during the late 3rd millennium BC in Scandinavia (Allentoft et al. 2015) and Bohemia, and slightly later in the Netherlands, while R1b1a1b1a1a2-P312 subclades are found everywhere in Europe (Olalde, Brace, et al. 2018), except for northern Scandinavia, which suggests a bottleneck of hg. R1b1a1b1a1a1-U106 in migrating Bell Beakers in Jutland.
The main R1b1a1b1a1a2-P312 subclades R1b1a1b1a1a2b-U152, R1b1a1b1a1a2a-DF27, and R1b1a1b1a1a2c-S461 share an early TMRCA ca. 2500 BC. Nevertheless, only R1b1a1b1a1a2b-U152 lineages are found widespread in different EEBA provinces at the end of the 3rd millennium, including the Upper Danube, Iberia, Bohemia, Poland, and Hungary (Olalde, Brace, et al. 2018). R1b1a1b1a1a2a-DF27 is found early in a sample from Quedlinburg in central Europe (Mathieson et al. 2015), in Iberian Bronze Age samples (Valdiosera et al. 2018), and one much later among Longobards in Hungary (Amorim et al. 2018), with a clear bottleneck in south-western Europe, especially beyond the Pyrenées. R1b1a1b1a1a2c-S461 lineages are mainly found in Bell Beakers from Britain and later Bronze Age populations, in a bottleneck caused by the expansion to the British Isles (Olalde, Brace, et al. 2018).
Rarer R1b1a1b1a1a2-P312 subclades include R1b1a1b1a1a2d-L238 (TMRCA ca. 2500 BC), reported in an old Icelander (Ebenesersdóttir et al. 2018), and present mainly among modern peoples of Scandinavian descent, which may suggest its early expansion to the north; R1b1a1b1a1a2e-DF19 (TMRCA ca. 2500 BC), found in a Roman individual from Britain (Martiniano et al. 2016), and among modern northern Europeans; and R1b1a1b1a1a2f-DF99 (TMRCA ca. 2000 BC), found in an Early Medieval Longobard (Amorim et al. 2018) and among modern northern-central Europeans.
Due to the early TMRCA of R1b1a1b1a1a-L151 lineages, and to the occasional finding of early subclades of the most common lineages in distant territories, the split of hg. R1b1a1b1a1a-L151 in expanding clans must have happened early during the Yamna Hungary–early East Bell Beaker society. It is impossible, then, to assign any R1b1a1b1a1a-L151 lineage to a specific Early Bronze Age community, in spite of the known majority distributions in certain regions. The association of certain subclades with specific linguistic communities needs to be understood, therefore, as the product of gradual and successive Y-chromosome bottlenecks, and a simplification of the ancient picture based on the limited data available.
Studies of ancient European hydronymy, reflected in the so-called Old European pattern (Krahe 1964, 1949; Nicolaisen 1957), reveals a quasi-uniform name-giving system for water courses that shows Indo-European water-words and suffixes following rules of Late Proto-Indo-European word formation (Adrados 1998). This points to an ancient wave of Late Indo-European speakers that spread over northern, western, and central Europe, before the proto-historic Celtic and Germanic expansions, including the British Isles, the Italian and Iberian peninsulas, the Balkans, and the Northern European Plains up to the Neman River in Lithuania.
The expansion of the Bell Beaker folk, originally from their North-West Indo-European homeland in the Yamna Hungary–East Bell Beaker community (Mallory 2013), and especially the expansion of R1b1a1b1-L23 lineages, under further Y-chromosome bottlenecks of R1b1a1b1a1a-L151 subclades (Cassidy et al. 2016), should therefore be associated with the spread of these Old Europeans throughout Europe, where their dialects would later evolve into the majority of the attested Indo-European branches of Europe.