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Category Archives: Chalcolithic

SW Iberian plaques from the Chalcolithic

A new study gives us the opportunity to learn about the mysterious SW Iberian plaques from the Chalcolithic period.
Daniel García Rivero & Daniel J. O’Brien, Phylogenetic Analysis Shows That Neolithic Slate Plaques from the Southwestern Iberian Peninsula Are Not Genealogical Recording Systems. PLoS ONE 2014. Open access LINK [doi:10.1371/journal.pone.0088296]

Abstract


Prehistoric material culture proposed to be symbolic in nature has been the object of considerable archaeological work from diverse theoretical perspectives, yet rarely are methodological tools used to test the interpretations. The lack of testing is often justified by invoking the opinion that the slippery nature of past human symbolism cannot easily be tackled by the scientific method. One such case, from the southwestern Iberian Peninsula, involves engraved stone plaques from megalithic funerary monuments dating ca. 3,500–2,750 B.C. (calibrated age). One widely accepted proposal is that the plaques are ancient mnemonic devices that record genealogies. The analysis reported here demonstrates that this is not the case, even when the most supportive data and techniques are used. Rather, we suspect there was a common ideological background to the use of plaques that overlay the southwestern Iberian Peninsula, with little or no geographic patterning. This would entail a cultural system in which plaque design was based on a fundamental core idea, with a number of mutable and variable elements surrounding it.

Figure 1. Engraved plaques from the Iberian Peninsula.
a,
Valencina de la Concepción, Sevilla, Spain (Museo Arqueológico de
Sevilla [MAS]); b, S. Geraldo, Montemor-o-Novo, Évora, Portugal (Museo
Nacional de Arqueologia de Portugal [MNAP]); c, Monsaraz, Reguengos de
Monsaraz, Évora (MNAP); d, Mora, Évora (MNAP); e, Jabugo, Aracena,
Huelva, Spain (MAS); f, Ciborro, Monte-o-Novo, Évora (MNAP); g, Marvão,
Portalegre, Portugal (MNAP); h, Estremoz, Évora (MNAP); and I, Pavia,
Mora, Évora (MNAP).

Rather than dwelling in the central discussion of the study, which is to empirically discard the genealogical hypothesis (for which it is surely best to read the paper as such), my main interest is to share this not often seldom discussed Chalcolithic phenomenon which is limited to SW Iberia (i.e. Southern Portugal and nearby areas of Spain). This study gives us the opportunity of not just knowing it but also contemplate its unity and diversity from a large number of specimens. 

Fig. 2 –  General design of the plaques.
The dates of the “plaque idols”, as they are often known in the literature, range from c. 2650 to c. 2100 BCE[see note below], corresponding to the development of the first Iberian (and West European) civilizations (fortified towns) in the area, which began c. 2600 BCE, with two main centers around modern Lisbon (Zambujal) and Almería (Los Millares) but that also knew of other such towns especially in Southern Portugal. All that in the context of dolmenic Megalithism, with the introduction of new burial designs such as the tholos (beehive tomb) or the artificial cave, innovations that may have been restricted for some elites. 

Important note (update Feb 25): the dates given in the previous paragraph are uncalibrated (i.e. raw BP minus 1950). The calibrated dates are quite older: between c. 3500 and 2600 “actual years” BCE, as you can check in table 1. They still overlap with the known dates for Los Millares (c. 3200–2300 BCE) and its “Almeriense” precursor culture but less so with Zambujal (c. 2600-1300 BCE, subject to possible revisions). My apologies for the confusion.

The most dense area, and seemingly also the most diverse, for this kind of findings is the southern part of Évora district (Central Alentejo, near the Guadiana River, known as River Ana in Antiquity), a mostly flat country with some low hills (the highest peak in the district has 600 m.) and a scattered natural forestry of corks and holm oaks. It was once known as Portugal’s “bread basket” and was surely of relevance in the Neolithic and Chalcolithic period, especially in relation with the development of the influential burial style of dolmens or cairns (known as mamoas in Portuguese), later partly replaced by tholoi.

Typical Alentejo landscape (CC by Alvesgaspar)

The plaques’ phenomenon is anyhow found through all the Southern half of Portugal, with limited penetration into Spanish Extremadura. Another important region was the Lisbon Peninsula, which was almost certainly a more important civilization and geopolitical center, with notable urban development in this period and becoming a major center of Bell Beaker.
Its main city, Zambujal (Torres Vedras) still barely researched was connected to the Atlantic Ocean by a 10-14 km long marine branch that was silted (tsunami?) at the end of its occupation (end of Bronze Age?) Hence we are talking of a major city (for the standards of the time at least) which lasted for more than a thousand years and whose influence encompassed once at the very least much of Southwestern Europe (and, if we accept that it was at the origins of the Bell Beaker, then all Western Europe and parts of North Africa).

Ruins of Zambujal (source)
Reconstruction of the known area of Zambujal, possibly just an acropolis (source)
Figure 3. Character states used in the analysis.

Back to the plaques, I don’t feel able to say anything about them that is not in the paper (read it and browse the many figures, please), except for one thing: some of the characteristics of certain plaques compare well with other “religious” iconography from the Southern Iberian Peninsula in Chalcolithic times.

For example plaque A in figure 1 clearly has the “oculado” (eyed) symbol found in many other artistic elements of the time and believed to represent some divinity and very likely representing the eyes of an owl (suspected to have been an ancient divinity or divine symbol in much of Europe, and found also in India).

“Oculado” symbol in a bowl from Los Millares (CC by José-Manuel Benito Álvarez)
An “oculado” idol (CC by Luis García (Zaqarbal))
Proto-Chorintian owl (public domain, credit: Jastrow)

Other plaques with a more defined head (plaque G in fig. 1, NK2 in fig. 3), remind also to the Millarense “cruciform” idols:

(CC Museo de Almería)
Diverse types of idols from Chalcolithic Iberia (source)
So I would think that all or at least many may well represent the same kind of divinity, possibly related to the origins of several more historical deities such as Athena (Greece) or Mari (Basque Country). 
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First ever bronze was smelt in the Balcans

It seems that West Asia is losing a bit of its relevance as the origin of nearly every development. Much as the first steel is now known to have been made in Central Africa several centuries before the Hittites (or not: see update below), the first bronze (“tin bronze” to be specific) seems now to have been made in the Balcanic peninsula, more than a thousand years before it was in Mesopotamia.
Miljana Radivojevíc et al. Tainted ores and the rise of tin bronzes in Eurasia, c. 6500 years ago. Antiquity 87 (2013). Freely accessibleLINK

Abstract

The earliest tin bronze artefacts in Eurasia are generally believed to have appeared in the Near East in the early third millennium BC. Here we present tin bronze artefacts that occur far from the Near East, and in a significantly earlier period. Excavations at Plocnik, a Vinca culture site in Serbia, recovered a piece of tin bronze foil from an occupation layer dated to the mid fifth millennium BC. The discovery prompted a reassessment of 14 insufficiently contextualised early tin bronze artefacts from the Balkans. They too were found to derive from the smelting of copper-tin ores. These tin bronzes extend the record of bronze making by c. 1500 years, and challenge the conventional narrative of Eurasian metallurgical development.

The specific well-dated finding is from Plocnik, Southern Serbia, however as we can see in the map below, most 5th millenium bronze sites are from Bulgaria.

This highlights the likely central role in this earliest bronze metallurgy of the Karanovo-Gumelnita culture (very likely a full-fledged state older than dynastic Egypt), which spanned most of Bulgaria, as well as some nearby regions by the south and the north. However the neighbor cultures of Gradesnica-Krivodol (NW Bulgaria and nearby Romanian areas) and Vinca (Serbia) were also involved.
The highest quality alloys (stannite bronzes) belong to this core area of Thrace (Karanovo, Smjadovo and Bereketska Mogila), as well as Southern Serbian sites (Plocnic and Lazareva) while a second category, “high tin fahlore”, seems to concentrate along the Danube (Gomolava and Ruse). A “low tin fahlore” category is rarer and seems centered in the Gradesnica area.
For some reason, maybe the disruptive Indoeuropean invasions of the 4th millennium, this technology was apparently lost later on, only to be regained from a West Asian source (Troy) already in the 3rd millennium.
An interesting question is the source of tin, which was in many cases the mineral stannite. The authors suggests further research on isotopes but also consider ancient mines that could have been sources:

Stannite is present in the Bronze Age mines of Mushiston in Tajikistan (Weisgerber & Cierny 2002), Deh Hosein in Iran (Nezafati et al. 2006), the Bolkardăg mining district in Turkey (Yener & ̈Ozbal 1987), as well as in Iberia (Rovira & Montero 2003).

The West and Central Asian mines are often argued not to have been sizable enough to be a major source of tin in the Bronze Age proper but, considering that this is a very early and limited bout of advanced metallurgy, I guess that they are also possible sources.

Update (Jan 22): I must (partly) take back my initial comment on steel metallurgy being older in Niger than Turkey: while the discovery of Nigerien steel-making c. 1500 BCE stands, other recent findings in Turkey seem to push back steel metallurgy in Anatolia to c. 1800 BCE (instead of the c. 1300 BCE date accepted before). Thanks to Aeolius for making us aware of this important detail.

Note: thanks to the Stone Pages newsletter ArcheoNews for directing me to this most interesting study.

 
 

Rhône-Provence Bell Beaker

Just a brief note on two French language papers from a decade ago that have shown up in my academia.edu alerts.
The most relevant one because of its wider scope is:
Olivier Lemercier, Muriel Pellissier & Yaramila Tchérémissinoff, Campaniforme et sépultures, au-delà du standard. La place du Campaniforme dans l évolution des sépultures du sud-est de la France au 3e millénaire avant notre ère. Proceedings of the International Conference held at the Cantonal Archaeology Museum (Sion, Switzerland), 2001. → available (with free registration) at academia.edu.

Abstract (only part in English)


Where are the famous Bell Beaker individual burials in the south east of France? What is the nature of the burials wherein we actually find Bell Beaker elements ? And what kind of Bell Beaker is it ? And also : where does the Bell Beakers stand in the evolution of the funeral architectures and rites between the end of the Middle Neolithic and the Early Bronze Age? Answering these questions, thanks to the presence of more than a hundred funeral sites in the area, would change our vision of the Bell Beakers fenomenon itself. These questions are also the occasion to present the diversity and the traditions of the funeral practices by the 3rd millenium BC.

I took some time to read it in spite of my limited skills at French (but it’s still Romance, so well… any educated Romance speaker can read it with some effort) and the overall conclusions are not too surprising: Bell Beaker is not only a burial thing, Bell Beaker appears in burial contexts of older local tradition, etc. 
The details and nuances are many more, of course. On one side the authors discern (much as it happens overall within European Bell Beaker) three groupings: 
  • Corded style in Ardèche
  • International style in the left margins of the Rhône
  • A local variant in the later period
Notice that the authors argue that both the Corded and International styles are roughly contemporary. I can’t judge this but, if real, it may mean a blow against the classical notion of Corded style being older and arriving to SW Europe via the Rhône. 
Another interesting aspect of the paper is that the authors argue for overall continuity of burial styles, which are varied:
  • individual burials with roots in early Neolithic
  • collective burials of both dolmenic-megalithic and cave typology
  • other rarer types, with a handful of examples each
Bell Beaker seems mostly related to collective burials, although in the BB period Megalithism seems to recede somewhat in favor of collective burials in caves, a tradition common in other parts of Europe, especially in the South and SW. This really casts all kind of doubts about BB in this region being able to be explained as some sort of migration from Central Europe (or anywhere else) because, unlike in this Indoeuropeanized area, BB individual burials as such are extremely rare; instead we must talk of BB elements inserted in local traditions of collective or “clannish” nature, just as we can see in Iberia and other Western areas where Indoeuropean influences was still non-existent. 
The other paper is:
Robin Furestier et al., 1974-2004 le site du Fortin-du-Saut (Châteauneuf-les-Martigues, Bouches-du-Rhône) et le Campaniforme 30 ans aprés. Congrès du Centennaire: Un siècle de construction du discours scientifique en Préhistoireavailable at academia.edu (registration needed as well).
This is about a particular Bell Beaker site near Marseilles, whose typology seems mostly influenced by the Portuguese VNSP civilizational center. Otherwise there is other non-BB pottery without decoration and what seems locally rooted stone tools and arrow points.
If you are fluent in French and happen to find out any error in my interpretation, please feel free to correct me in comments, thanks in advance.
 
 

Basque and other European origins according to ancient mtDNA

This is a (partly shortened) version of an article I wrote recently in Spanish language for Ama Ata.
For reasons of the variegated methodology used by the various researchers this comparison across time and space has to be simplified. Still it is a valuable insight on the demographic changes produced in the Neolithic and later on in three European regions: Germany, Portugal and the Basque Country. 
Germany
As you surely know already, the results of archaeogenetic sequencing in Central Europe have produced quite perplexing results: not just the Neolithic wave seems to have caused major changes but also this one was victim of similarly radical later changes in the demography. Visually:

The first period when we see an mtDNA pool similar to the modern one is already in the Late Bronze Age. However we lack data for all the early and middle Bronze Age and the data of the late Chalcolithic already points to the components of this modern pool being present, albeit in a very fragmented form. If anything there was still excess of L(xR), i.e. N(xR). 
This late Chalcolithic and Bronze Age knot of Central European demographic history is still to be solved. But something we can already say for sure: the Neolithic wave was of dramatic consequences in this region but itself was wiped out by later, still ill understood, secondary waves.
Portugal
This area is not so well documented, however the data we do have still provide a very interesting sequence of the demographic history of SW or West Iberia. Visually again:

One of the problems here is, quite evidently, that sequencing only the HVS-I region is not at all enough to identify some very important haplogroups, particularly H. We can reasonably think however that most or even all of the R* sequences are actually H.
We see some but not-so-radical changes with the arrival of Neolithic: some apparent decrease of U (halved) and L(xR), a +33% growth of H and first detection of HV0 (probably V). However these changes seem to have been partly countered by Chalcolithic, plausibly by means of blending between first farmers and more purely aboriginal populations. Overall I am very much tempted to think that the arrival of Neolithic to (South and Central) Portugal only caused mild demic changes. 
This fact, together with the extremely high frequencies of haplogroup H and the key role played by SW Iberia in the formation of Dolmenic Megalithism, as well as their pivotal role in Bell Beaker, including the existence of a major civilization (Zambujal, VNSP), the first one ever in Atlantic Europe, makes this area highly suspect as a possible origin for the spread of mtDNA H in Western Europe to the frequencies that we find today (c. 40-50%).
However we have only very limited archaeogenetic data from other Atlantic Megalithic regions and in general from Megalithic burials and it is at least possible that Armorica (Brittany, West France) or Denmark and the nearby Low Germany regions played important roles in this spread, which we see so dramatically exemplified in the German Bell Beaker sample. 
When the finger points to the Moon, the fool looks at the finger. Portugal could be the Moon but it may just be the finger, so I will remain cautious at this stage of research. Whatever the case it does seem to me that Megalithism is a likely source of that excess H (Bell Beaker being just the finger here, almost for sure).
I must add that there seem to be some important demic changes since Chalcolithic in Portugal. Tentatively I will attribute them to the intrusive SW Iberian “horizons” (proto-Tartessian?) and/or the Luso-Celtic invasions of the Iron Age. 
Basque Country
My main aim in all this compilation was, as in a sense in all my diving into prehistoric research for so many years now, to find an answer to the mystery of the origin of Basques and Basque language. 
In the last few years we have been blessed with some important and revealing archaeogenetic research in this area, and therefore I could build also an informative graph for the Basque Country:

Very synthetically, I think that we can see here, much as in Portugal, some not too radical changes with the Neolithic arrival, and then relative stability until present day. This is coherent with the Basque Country not having suffered effective Indoeuropean invasions, unlike Portugal.
However I strongly feel the need to look at the fine detail in the Basque Neolithic transition, because it has some interesting question marks:

Seen as that, it would seem like the Neolithic-induced demic change was more important in Navarre and less in the Western Basque Country. However the two Ebro basin sequences (both Fuente Hoz and Los Cascajos) are very high in U* and low in U5, which is so far the only U subclade sequenced in the Paleolithic of the Basque-Cantabrian area. At this point I do not really know how to interpret this fact nor even what kind of U sublineage is that one.
What I do know is that, on one side, the Biscay-Gipuzkoan area seems to have been initially unaffected by Neolithic demic waves and that the Paternabidea sequence is very very similar to modern day Basque average (and even more in its own sub-region).
It is very possible that the Basque periphery, notably the Ebro banks, suffered more intense demic changes than the core Basque areas of the piedmont. However, when compared with other European regions (very especially Central Europe) the Basque genetic pool seems quite stable since Neolithic times. 
Is Basque language Neolithic?
Even if genetics and language need not to be tightly related, of course, the question of the origin of Basque language and the proposed Vasconic language family, believed to have been spoken in much of Europe at some point in Prehistory, are indeed related to the genetic origin of the Basque people. 
There are four main models for the origin of Basque and Vasconic:
  1. Magdalenian (Paleolithic) origin in the Franco-Cantabrian region some 17-15,000 years ago (incl. possible sub-waves like Tardenoisian/geometric Epipaleolithic).
  2. Neolithic origin.
  3. Megalithic origin.
  4. More or less recent (Iron Age?) arrival, defended by mostly by the fanatics of Indoeuropean continuity. 
We can safely discard #4 only based on archaeology but the genetic aspect seems to add even more weight to this dismissal, after all it is Indoeuropean speaking peoples the ones which show obvious signs of demic change, sometimes very dramatic, not Basques.
Personally, and with due caution, I would also cast doubt on #1, partly because the Vasconic substrate area seems to include strongly many parts of Italy like Sardinia, in principle unaffected by the Magdalenian expansion, and I would also include at least to some extent parts of the Balcans (for example the Ibar river in Kosovo). 
So I am rather inclined for model #2, i.e. that Vasconic was the language family spoken by European Neolithic peoples with roots in Thessaly (pre-Sesklo→Mediterranean Neolithic, proto-Sesklo→Balcano-Danubian Neolithic). I cannot of course exclude a possible re-expansion of some of those languages within the Atlantic Megalithic phenomenon, which I would deem responsible of the expansion of much of mtDNA H up to modern frequencies, however I doubt this one is the source because it is difficult to explain the presence of Vasconic in many pockets in which Megalithism was at best very secondary or did not exist at all (for example most of the Ancient Iberian area, Sardinia, the Balcans, etc.)
So my tentative proposal is that there was a root Vasconic spoken some 9000 years ago in Thessaly (Northern Greece), which split (as per archaeology) in two branches:
  • Southern or Western Vasconic (Impressed-Cardium Pottery and related cultures, including the Megalithic urheimat in Portugal). 
  • Northern or Eastern Vasconic (Red-White Painted Ware in the Balcans and later Linear Pottery in Central Europe).
Basque, ancient Sardinian, Iberian and the hypothetical lingua franca associated to Megalithism would belong to Southern Vasconic. Danubian Neolithic peoples would have spoken Northern Vasconic instead but, as we can see, they were eventually all but wiped out by secondary arrivals from West and East. Even the very Balcanic core areas of Thessaly, Macedonia and Serbia also suffered an invasion early on by peoples with Beige-Black pottery (Vinca-Dimini) surely related to Tell Halaf. So the main survivor to the Metal Ages was Southern (Western) Vasconic, which was then wiped out (excepted Basque) by the Indoeuropean invasions of Celtic and Italic peoples. 
We can still see fossils however. One of my favorite examples is the Latin particle bi- (as in bilateral, bilingual, etc.), which seems derived from Vasconic bi (two, at least in modern Basque) and unrelated to PIE *dwos. Also the English words kill and ill, which seem related to Basque verb hil(-du) (pronounced /hill/ or /ill/ and meaning to die or to kill, depending on how you conjugate it). Again both English terms do not have any apparent PIE origins, although they may derive from proto-Germanic. These are just examples, of course, there seems to be much more to be researched.
Appendix: detail of the data and bibliography: LINK.
 

Echoes from the past (August-28-2013)

Oh, yeah, I admit it: I have been procrastinating a lot. Result: an extremely long “to do” list. Naturally, I can’t make up for all the past laziness, so here goes a synthesis of what would otherwise be left unattended, take your time, please. 
Middle Paleolithic:
Atapuerca holds “uninterrupted” sequence of European humans since 1.2 million years ago. Soon-to-be-published theory of continuity from H. erectus to Neanderthals in the Castilian site → Paleorama[es], EFE Futuro[es].
More Neanderthal evidence for symbolism found in Fumane cave (Veneto, Italy): polished and ochre-painted shells (pictured) → PLoS ONE (open access), El neandertal tonto ¡qué timo![es].
Upper Paleolithic:
Epigravettian burial, dated to ~14,000 BP, found in Cuges-les-Pins (Provence). The Epigravettian (and not the more widespread Magdalenian) culture of this site indicates a direct link to Italy → INRAP[fr], La Provence[fr], Los Andes[es].
Oldest modern human remain of Galicia found at Valdavara cave (Becerreá, Lugo province). The milk tooth is 17,000 years old, 7000 years older than any other such finding in the NW Iberian country → Pileta[es], IPHES[cat].
Epipaleolithic:
Thousands of engravings, dated to c. 6000 years ago, found in Coahuila (Mexico) → RTVE[es].
“World’s oldest calendar” found in Scotland → BBC.
Female burial found at Poças de São Bento (Sado basin, Portugal) → Paleorama[es].
Neolithic:
First farmers were inbred (at least in Southern Jordan) → Science Magazine.
Qatar Neolithic dig shows the peninsula was in contact with early Sumerian civilization (Eridu or Ubaid period, the first empire ever) → The Archaeology News Network.
Manure was already used by Europe’s first farmers → Science.
Chalcolithic:
Haryana (India) town is oldest large IVC settlement → Business Standard.
East China engravings show first Oriental writing (~5000 years’ old, just slightly younger aged as Sumerian cuneiform writing but much more recent than the controversial Tărtăria tablets of Bulgaria) → The Guardian, English People.
North American natives caused lead pollution in Lake Michigan (oldest recorded) → PPV paper (ER&T)University of Pittsburg.
Perdigões enclosure and collective burial was pilgrimage center. Antonio Valera (often so scholarly cryptic at his blog) loosens up when interviewed by a Portuguese publication, giving meaning to the archeology he’s working with → Super Interesante[por].
Bronze Age:
Cypriot harbor city dug: Hala Sultan Tekke, near modern Larnaka, had 25-50 Ha. and was active between the 16th and 12th centuries BCE → The Archaeology News Network.

Also from Cyprus: large settlement dug out near Nicosia (Cyprus), dated to 2000-1500 BCE → The Archaeology News Network.
Human evolution:
Modern human shoulder much more efficient than chimpanzees’ at throwing… but also than H. erectus’ → BBC.
Neanderthals did speak (of course) → Science Daily, open access paper (Frontiers in Psychology).

Note: their unfounded insistence on most unlikely H. heidelbergensis shared origins of Neanderthals and us casts some doubt on elements of their reasoning however.

Genetics:
Record ancient DNA: ~700,000 years’ old horse sequenced → Nature Communications (PPV).
Experimental archaeology:
How to carve your own stone tools and weapons out of modern materials: very interesting videos (in English) at Paleorama[es] (scroll down). 
More tomorrow (nope my “to do” list is not at all finished with this entry).
 

Revisiting the demographics of Northern and Central Europe in the Neolithic and Chalcolithic periods

Stimulated by the discussion at another entry, yesterday I made a little graph, almost a mnemonic, on the demographics of Northern European Neolithic and Chalcolithic, based on academic data which I discussed back in 2009.
This is the result:

The very simplified graph is nothing but a version of another one, used in 2009 (and reproduced below), which in turn is an annotated and composite version extracted from two different studies (references also below).
For convenience I have marked the millennia marks at the bottom (meaning 5000, 4000, 3000 and 2000 BCE, from left to right) while the unmarked vertical scale ranks from 0 to 100 (marked by the lowest and highest dots, not the frame, which is actually outside of the graph itself). The dots mark population level at any time as proportion of the maximum (100) in discrete intervals rounded up/down to 10 ppts and taken at intervals of 250 years. Notice that I ignored monuments in the case of Britain, only considering the habitation and other productive sites.
Not sure if it will result useful to you but it did help me to visualize the demographics of Northern Europe in these four millennia of surely dramatic population changes. If you don’t like this version the more detailed original double graph is below, scroll down.
Something quite obvious is that while Danubian Neolithic first caused an important population expansion, it later declined to quite low population levels, maybe because of climatic cooling and the exhaustion of the lands because of poorly developed agricultural techniques. 
This late Danubian collapse lasted for about a millennium, when (1) Funnelbeaker (TRBK) in Denmark, (2) Megalithism in Britain and Denmark especially (later also in parts of Germany) and (3) Kurgan cultures in Poland (later also in Germany and Denmark) seem to have brought with them very notable demographic expansions.
But decline seems to set on again all around at the end of the Chalcolithic period, much more notably in the continent (in Poland the rate of archaeological findings decays to zero!) than in Britain and especially Denmark. 
And now indeed the original “verbose” graph:

And the sources:
 

New Maya city discovered

Archaeologists have discovered the ruins of a long lost Maya city in the jungle SE of Campeche state (Yucatan Peninsula, Mexico), in the historical Maya region of the central lowlands. 

The newly discovered city, Chaktún, occupies some 22 Ha. and is believed to have been an important local power between 600 and 900 CE. It was hidden in the northern area of the Biosphere Reserve of Calakmul, near the Guatemalan border.

Source: Paleorama[es].