O2b and other Y-DNA from Korea and surroundings

In another discussion, Terry brought up this recent paper on O2b and Korean patrilineages (with important references to the rest of East Asia) that I believe is worth mentioning:

Soon-Hee Kim et al., High frequencies of Y-chromosome haplogroup O2b-SRY465 lineages in Korea: a genetic perspective on the peopling of Korea. BMC Investigative Genetics 2011. Open access. 

Much of the paper is tainted by insistence on lineage age speculations (TMRCA) which help nothing, are unscientific and induce confusion. However I do find interesting that they seem to find (figure 3) that SE Asian instances of O2b (O2b* and O2b1) are derived and not ancestral in relation to NE Asian ones. Hence the occasional O2b found in SE Asia (Indonesia, Vietnam, Thailand, etc.) looks like having originated in Korea or nearby. 

On the other hand the haplotype neighbor-joining structures for O3 and C still look like rooted in the South. In relation to NE Asian C (C1 and C3) I find most curious that a single Korean haplotype would seem to hold together C1 and C3, maybe indicating a joint origin within C for these two NE Asian haplogroups.

Overall I get the impression of a South to North colonization in East Asia, which pretty much set the fundamentals of modern population genetics in the whole region. This process was surely followed at a later time by some North to South backflow, which does not need to be “Neolithic” (beginning in South China at least as early as in the North) nor “Han” (in many cases the relevant haplogroups are definitively not found among North Han but Koreans, Japanese, etc.), it may well be, at least partly, related to the extension of blade industries since c. 20 Ka ago, phenomenon that might have got a southwards pointing vector. 

In any case, an important reference for data miners. 

 

74th anniversary of the destruction of Gernika

Gernika Oak (source)

Gernika is the only town I know in the Basque Country that lacks of an old quarter. Everything, excepting some peripheral buildings, is new, built in the last seventy or so years.

Gernika and not Guernica, mind you, because Gernika is the Basque spelling and also the Spanish spelling Guernica is misleading in English, making people mispronounce Gwarnikah, when it is actually Garnikah – pronunciation is exactly the same in both languages: Basque and Spanish, only spelling changes. 

74 years ago the town of Gernika, the historical capital of Biscay, was totally destroyed by the systematic bombardment by the Nazi Condor Legion, sent to support the fascists in spite of the supposed international embargo to both fighting sides. This fact underlines that United Kingdom (more or less reluctantly seconded by France) supported the Fascist side in the Spanish Civil War, by means of impeding the legitimate government from getting international support (only some lesser, costly and highly conditional Soviet support arrived besides the enthusiastic but ill equipped international brigades), while the Fascists got all the support they wanted and more from Italy and Nazi Germany.

Before the destruction (source)

In fact they were Italian brigades the ones that marched over most of Biscay after German airplanes bombed not just Gernika but also Durango and other localities. In fact it was largely an Italian and German full fledged invasion with the complacency of Great Britain, who forced France to accept this arrangement (and later used it as cannon fodder against Germany in WWII anyhow). 

74 years ago, in April 26 1937, at 15:37, sirens scared the town. It was monday, market day. For the first time in history a town was totally razed by an air bombardment. Years later, as other cities like Dresden or Hiroshima were also totally razed in the course of WWII, Gernika would seem by comparison pecata minuta, but in it its day it truly impressed the global collective psyche. It was not so much the few thousand dead (not many compared with the million who died in the whole war) but the fact that a civilian town had been so barbarically razed, looking to cause terror rather than military goals. 

In addition the town, as historical capital of Biscay, held and still holds an oak tree that was symbol of Basque freedoms, under which the Parliament of Biscay had been gathering since memory exists, since at least the 11th century (eventually a building was built by the tree). and where the monarchs of Castile (later Spain) took oath of respecting the Basque self-rule. Then of course the painting by Picasso also helped to emphasize the horror and confusion that such a war crime caused all around.

(source)

A few days later the Italian columns took the whole district, marching on an ill defended Bilbao, from where I now write these lines, and from there westwards to Cantabria and eventually Asturias too. Eventually they would take the whole state, ending the Republic and suppressing the long-lived self-rule of Biscay and Gipuzkoa. The scars of this war and the fascist dictatorship that ensued for decades, effectively destroying two generations, still persist. 

Because, Gandhi dixit, violence engenders violence.

The “Guernica” to Gernika (in Gernika)

 

Bamboo knives? Darts?

Bar-Yosef splitting bamboo with simple stone tools

There is a long held idea among prehistorians that maybe, only maybe, the peoples of SE Asia used bamboo-made tools instead of stone-made ones, what would explain the relative scarcity of stone tools in this area before the Hoabinhian (or rather its predecessor: the Son Vi culture) and the fact that they are mostly flakes and cobbles, not blades.

The hypothesis was floating around for decades but was never, I understand, tested in any practical way. Now a team lead by O. Bar-Yosef and manned by the expert hands of knapper Metin E. Eren, have attempted to reproduce these alleged bamboo knives.

They found that making with the simplest stone tools them was relatively straightforward (see video) but that, once created, they’d lose their edge quickly. Also the ability of bamboo knives to cut hides was poor even if they are useful to cut meat.

On the other hand, Eren was able to produce which is maybe the most critical bamboo tool needed: a spear or dart. While bamboo knives were surely useless in comparison with simple stone flakes, bamboo darts may have been a critical component of the Paleolithic toolkit: the hunter’s weapon.

Of course, bamboo proved itself ideal for basketry and container creation.

Ofer Bar-Yosef et al., Were bamboo tools made in prehistoric Southeast Asia? An experimental view from South China. Quaternary International, 2011. Pay per view. 

Direct sources:

• SMU Research Blog: Bamboo tool-making study shines light on East Asia’s Stone Age tool scarcity
• Related Flickr photo gallery
• Related video

 

ArchaeoNews April 23

A quick review to some of the most interesting archaeological news from the Stone Pages‘ news bulletin:

Europe

Oldest (c. 6000 years ago) European depiction of magic mushrooms (Psylocibe sp.) is in Central Spain (left). An even older one is known from Algeria (c. 9000 years ago). (New Scientist).

A very interesting research article by George Nash et al. on the Llwydiarth Esgob stone can be found at Past Horizons.

Neolithic houses found under modern ones in Saxony (Germany) (Google – Canadian Press).

South Asia

Dolmen burials discovered in Central India. The newly found megalithic sites near Nagpur are among the northernmost ones of this Iron Age cultural and spiritual phenomenon (Times of India).

East Asia

Before the outrigger?

Bamboo knives excellent for meat but awful for hides, and they dull quickly. Practical research by O. Bar Yosef, M.I. Eren and others sheds light on the bamboo knife speculations regarding Eastern Asian Paleolithic (SMU Research Blog). This is so fascinating that I’ll write a separate entry later on.

Rising Seas transformed rice farmers into fishermen at Fuzhou (SE China), what might have triggered the Austronesian expansion (New Scientist)

America

Oldest cloth from Peru (left) is 12,000 years old (Past Horizons, Eureka Alert)

7000 years old human remains found in Iowa during sanitation works (Fox News)

 

The Africanness of Europeans (and West Asians)

Sincerely not my ideal of research on population genetics but this new paper still offers some stuff to chew on:

Priya Moorjani et al. The History of African Gene Flow into Southern Europeans, Levantines, and Jews. PLoS Genetics, 2011. Open access.

An important bias is the lack of other West Asian or North African references. The paper deals with Europeans, Jews and Palestinians (with emphasis in the comparison with the Yoruba outgroup YRI) and that’s about it (we also find Turks in the supplements). This has interest, of course, but also has huge limitations. 

Specially problematic, considering that the paper tries to study an apparent African component in West Eurasian populations, is the lack of North African references. 

The authors fail to see it but for me it is transparent that what they identify as “African admixture” is nothing but North African admixture, surely related to the expansion of Y-DNA E1b (though not strictly so). The origin of this lineage is surely in NE Africa, around modern Sudan, and arrived to West Asia and Europe surely by two main routes:

1. Via West Asia and Greece and then with the Neolithic flows.
2. Via West Iberia and then through the Atlantic (mostly) with Dolmenic Megalithism.

In order to illustrate my point, I shall borrow here an image from a previously discussed paper:

The YRI component vanishes when Iberians and NW Africans are directly compared

The authors also pretend to be able to pinpoint the approximate age of such alleged (and ill understood to them) “admixture” but their dates make no sense whatsoever. At least not for me. So I’ll ignore that part.

We lack of a good source population: HapMap Yorubas YRI can only be a proxy outgroup and the various Palestinian groups can only be an already much admixed proxy. But estimating from several sources (including this PCA, from this earlier entry) I believe that the “YRI admixture” approximates 1/3 of the true admixture with the original Low Sudanese or Upper Egyptian main true source (?) of West Eurasian Africanness.

So all the results should be multiplied by three to estimate the apportion of “Nubian” input. A “Nubian” true original population is anyhow an approximation, because in the Iberian case most of the Africanness is in fact of Moroccan or otherwise NW African origin, with no immediate ties with Sudan (E1b1b1b1-M81). 

If so, I estimate, based on table 2 (and multiplying by three), that there is roughly the following fractions of Nubianness:

• Palestinians c. 30%
• Portuguese c. 6% (notice that the actual amount of North African component in West Iberia is more like 9%, so we are underestimating here the real “Moroccanness” by 50% – this is probably because Moroccans are quite less Yoruba-like than Nubians)
• South Italians c. 5%
• Spain c. 3% (4.5% is probably more realistic for “Moroccanness”)
• Sardinians and North Italians c. 0.6%
• Ashkenazi Jews c. 8%
• Other Jews c. 12%

Whiter than thou…

And that would be what I’d have to say on this only somewhat interesting paper but I happened to dig into some of the supplementary material and I’d say that fig. S1 has some interest. 

Of course it has some interest for those who enjoy racialist (tending to racist) comparisons. The lack of other outgroups like East or South Asians, allows for a very black and white (literally) reading of this material. That’s why the title of this section, because in most racialist forums there is not going to be a blacker than you argument, certainly not involving European populations.

Interestingly there are very few populations whiter than HapMap’s CEU sample. As you may know this strange sample that pretends to represent Europeanness in so many simplified genetic studies is made up of Caucasoid people from Utah (USA): it’s not even a true European sample. However it seems representative enough for English-plus (most white Utahns claim English or, some, Danish ancestry, according to US census data).

Following fig. S1, most populations are actually blacker than CEU, so to say, i.e. they tend towards YRI at least slightly more than CEU. I could only spot two exceptions: Orcadians and  Basques. So we can well say that CEU are, at least in contrast to Africa, a paradigm of Europeanness (after Orcadians and Basques) – however no judgment can be made in relation to other outgroups (from Asia) based on this paper’s data.

Some significant structure within Europe

An interesting element in this supplemental fig. S1 is the second (vertical) dimension. In most tripartite comparisons between CEU, YRI and another European population, CEU and the other Europeans overlap in the second dimension, which only reflects diversity within Yorubas themselves. I understand that if Yorubas are more internally diverse than these two European populations, the potential structure between NW Europeans (CEU) and the compared third population is not-significant, trivial, irrelevant. 

This is the case for: Swedes, Irish, Germans, German-Swiss, Belgians, Scots, Orcadians, Dutch, French-Swiss, French (two different samples), Polish, Austrians, Hungarians, Czechs, one of the two Russian samples (POPRES), Spaniards, Portuguese, Bosnians, Croatians, Romanians, Greeks, one of the two Italian samples (CEPH-HGDP), Tuscans, Italian-Swiss. This was also the case for Turks (not technically European) but not for any of the other West Asian (Palestinian) samples nor the Ashkenazi Jewish one (which is the most Europanized of all Jewish subgroups). 

Among Europeans, a number of populations show more structure in comparison to CEU (and hence the majority of Europeans) than Yorubas show among themselves, defining a second dimension in intra-European terms. These “outlier” European populations are:

• Basques
• Russians CEPH-HGDP (which I believe are from the Far North and have probably a strong Finnic component)
• Italians POPRES (which are partly from the South – North Italians alone did not contrast much with CEU)
• Sardinians

In addition all the Palestinian groups (“Palestinian”, “Druze”, “Bedouin”) also show such contrast with CEU, as do Ashkenazi Jews but not Turks.

Follow the four relevant eigenvector graphs:

Comparison with Basques

Comparison with POPRES Italians

Comparison with Sardinians

Comparison with CEPH-HGDP Russians

 

Haplogroup O3 downstream structure refined

A new paper has revised some details of the phylogeny of Y-DNA haplogroup O, specially of O3:

Shi Yan et al.,  An updated tree of Y-chromosome Haplogroup O and revised phylogenetic positions of mutations P164 and PK4. European Journal of Human Genetics, 2011. Pay per view. [doi: 10.1038/ejhg.2011.64]

A copy of the paper can be read (for a year) here.

Most importantly, three subclades (O3a1, O3a2 and O3a4 prior to this review) have been joined in a single subclade of O3a that gets the name O3a1, defined by newly described mutations L127, KL1 and KL2.

Former O3a3, the most common lineage in China, is now relabeled O3a2 (per the paper’s proposal) and subclade O3a3b2 (P164) goes up in the hierarchy as O3a2c, absorbing its “uncle” (O3a3c – M134) as a subclade (now O3a2c1) and becoming independent from its former “father” lineage O3a3b (M7), which retains the name.

Another subclade moved up in the phylogenetic hierarchy is former O2a1a (PK4), which is now revealed to be ancestral (and not descendant) to former O2a (M95). 

Figure 1 should help understanding these changes:

click to expand

The three regions (East, North, South) refer to regions of China (rough references: Shanghai, Beijing and Guangzhou respectively, I guess). Most haplogroups are quite evenly distributed but some are only (or almost only) found in the South. These are (by the new nomenclature):  O1a2, O2a*, O2b and O3a2a. Inversely O3a1a is not found in the South (dominant in the East instead). Notice that because of the samples being taken from students at a Shanghai university, East China is oversampled.

A discussion in Chinese can be found also in this Forum of Molecular Anthropology. Thanks to Natsuya for the info.

 

A one-dimensional universe at the Big Bang?

This is so weird and intriguing that I can’t but make a quick comment on it. Two US scientists, Jonas Mureika and Dejan Stojovic, are proposing a radical rethink of what we understand as the basic physics of our universe: they suggest that, at the Big Bang, the Universe had only one dimension (like a line), acquiring then two dimensions (plane) and then three (space), and probably soon a fourth (if not already). 

This radical rethink seems to have been pushed by the advances (and lack of them) in the fields of Physics and Astrophysics in the last decades, when questions have been piling up and convincing answers have been lacking instead. 

These problems include the fundamental incompatibility between gravito-centric General Relativity and particle-centric Quantum Mechanics, the mystery of the Universe’s accelerating expansion (which seems to demand extra dimensions) and serious issues with the elusive (and maybe non-existent) Higg’s Boson. 

By reflecting this new proposal I do not mean to adhere to it but I do like the principle they begin from: maybe something fundamental is wrong in the way we think Physics, so exploring radically new venues may be the way out of an otherwise unsolvable problem. 

They are thinking out of the box and that is something I really like and that often brings real solutions in all fields. 

The new theory has been published in the Physical Review Letter (pay per view) and is also discussed in its essentials at Science Daily.

 

Stoning at Dmanisi

H. georgicus

Lots of cobbles have been found in a gully near Dmanisi, Georgia, the oldest known site of Homo erectus (or habilis or georgicus) in Eurasia. The cobbles could not have arrived there naturally and are not found in other areas of the site (Olduwayan style tools have been found instead). 

The researchers suspect that the abundance of cobbles in the gully was caused because it was a pass our ancient relatives used to attack carnivores, by stoning them, and rob them their prey. The unusually high frequencies of carnivore bones in the site would seem to support this kind of strategy and ratify our earliest relatives as active scavengers who could rob their prey to other predators by using the skills nature gave them: sociality, intelligence and two free hands. 

Full story at The Great Beyond (found at Archaeology in Europe).

 

Guest post by Argiedude: A West-East Y-DNA gradient in Iberia?

What follows was sent to me by Argiedude with offer of publishing. I believe it has some interest, so here it is, however publication does not necessarily imply agreement by the blog’s author (see comments section).

_____________________________

I’ve made a map of the main y-dna haplogroups of Iberia, using all the y-dna studies I could find, totaling some 3000 Spanish and 2000 Portuguese samples, though it varies depending on the haplogroup. The graph below shows the results:

click to enlarge

There are 10 haplogroups, excluding SRY-2627 and M153, which are redundant with R1b1b2. 7 of the 10 have clear east-west gradients. The other 3 have no gradient, though for G a weak east-west gradient could be argued. None have a north-south gradient.

Not only is there an east-west gradient, but it follows a specific pattern, dividing Iberia into 2 halves. And there is a curious anomaly in the otherwise perfect 2 halves, which can be easily seen in the image below:

Valencia, in the far east, consistently has a y-dna composition that is more akin to western Iberia. The image even underestimates this similarity, because E-M81 is higher in Valencia than in the rest of east Iberia, but it just barely didn’t make the threshold to be included with the western half, so the image shows Valencia as scoring 4 of 6 similarity with western Iberia when it should perhaps be 5 of 6 (after including E-M81). I didn’t include a few haplogroups because they were too small (1% or less frequency), but 2 of them, E-M123 and E1a1+E1b1a, also had a frequency peak in Valencia higher than in the rest of  east Iberia and similar to western Iberia. So I don’t think that the results for Valencia are random. As a final note, Valencia consisted of 300 samples, which is a respectable sample size.

The frequencies in the western half seems to be more uniform, while the frequencies in the eastern half are more jumpy. In particular, the west coastal strip, from south Portugal to Galicia, is remarkably similar, in all haplogroups. I think the y-dna of Iberia used to be like western Iberia today. There was a disruption that altered the eastern half. This would explain the anomaly of Valencia: it wasn’t as badly affected by the disruption as the rest of east Iberia, thus retaining a more western y-dna composition.

IMPLICATIONS FOR TMRCA

E-M81 has one of the youngest age estimates (TMRCA) of any major haplogroup, about 2000 years old. The first image shows it to follow the typical east-west pattern in Iberia almost perfectly, second only to R1b1b2 (which is perfect). So was E-M81 part of the original older stratum of y-dna in Iberia? This would fly in the face of the TMRCA age estimates for E-M81. E-M81 is so young, and at the same time identical in haplotype to North African E-M81, that we are forced to adscribe its presence in Iberia to the Arab invasion starting in 700 AD. But the maps paint a completely different picture, not only showing a geographic distribution that makes no sense at all with a historic Arab origin, but also because E-M81’s notorious similarity to the repeat pattern of east-west distribution seen in most other haplogroups indicates that its distribution must have been molded by whatever events also produced the distribution patterns in all those other haplogroups. It seems extremely unlikely that E-M81 would have been born 2000 years ago in North Africa, became diffused in Iberia between 700 AD and 1200 AD, and only then something occured which rearranged Iberia’s y-dna, all of it, into the now observed patterns of east and west halves. This unlikely scenario would have to be nothing less than a complete and total population rearrangement, no half measures, given that E-M81 is actually higher (much higher) in regions barely occupied by the Moors than in the stronghold of Granada, where the Moors ruled for 800 years.

It should also be noted that North Africa has 2 major haplogroups, E-M81 and J1-L222, found at about 50% and 25% respectively, from Morocco to Libya. But in Iberia, while E-M81 is present at 4% in Spain and 5% in Portugal, J1-L222 is not found at all in Portugal and is only found at 0.05% in Spain. This is also repeated in thousands of Latin American samples, where E-M81 is about 4% and J1-L222 is 0.1%. A historic recent diffusion from North Africa would obviously have spread 2 E-M81 samples for every 1 J1-L222 sample, as per their frequencies in North Africa, but instead we see that the ratio between E-M81 and J1-L222 in Iberia is 75 to 1. Likewise in south Italy the ratio is 20 to 1.

To summarize, on top of previous evidence over the last 2 years undermining the extremely young age estimate of E-M81, which consisted of the obvious east-west distribution of E-M81 in Iberia and the anomaly of J1-L222 not being found even close to proportion with the presence of E-M81 in Iberia, we can now add the fact that E-M81’s distribution in Iberia isn’t an oddity, but in fact the typical pattern of distribution of most Iberian haplogroups, which obviously points to deeper causes for its diffusion in the peninsula, unless Iberia’s population has been completely and totally rearranged in very recent history. This is not just about Iberia, but about the theory of TMRCA itself, which as you may have guessed by now, I completely disagree with: I think all y-dna haplogroups are older than their currently estimated ages (per TMRCA) by orders of multiples.

A final note to round out this observation is the fact that most haplogroups are higher in the west than in the east, which sometimes really doesn’t make sense, most notably in the case of E-V13, which would have come from eastern Europe via land and should have had a higher frequency in east Iberia.

ODDS AND ENDS OF IBERIA’S Y-DNA

Ibiza has 2 clusters specific to its island in the haplogroups G and T. The cluster in G has a modal haplotype identical to the general G haplotype, but the T cluster has a very distinctive modal haplotype, which I haven’t found in any sample from anywhere else in Iberia or Latin America; so far, it’s only observed in Ibiza, not even Majorca and Minorca.

There’s something strange going on in the Cantabria/Basque region. Cantabria has an unusually very high rate for R1a and E-M81, and the Basques for R-M153. Very few regions have any single haplogroup with a highly divergent frequency, but these 2 neighbors manage to have 3 such events. The y-dna differences between Basque and Cantabria are the sharpest y-dna clines by far in Iberia. And of course, Cantabria belongs to the western half and the Basques to the eastern half of the Iberian y-dna divide. Cantabria’s R1a and E-M81 seem to extend westwards, resulting in lower but still unusually high frequencies of both haplogroups in Galicia, Asturias, and Castile, but in both cases the haplogroups can’t manage to diffuse eastwards even as far as the Basque region. Likewise, R-M153, very high in the Basque region, has a notable tendency to spread to the rest of east Iberia, but it can hardly manage to cross west into Cantabria and beyond.

The haplogroups I included in these images amounted to 93% of Iberia’s y-dna. Most of the remaining 7% belonged to E1b1b (M35) lineages, except E-M81 and E-V13.

click to expand

_____________________________

See also at Leherensuge (by Maju):

• Iberian Y-DNA (the one closest in content to this article)
• Neolithic spread in Iberia: the Y-DNA perspective (related to the previous)
• Pyrenean Y-DNA
• Several posts on R1b1b2: 
• R1b1b2a1 is almost exclusive of Western Europe
• Finally some good research on R1b1b2
• Again on Neolithic and European Y-DNA
• R1b1b2a1 neolithic or what?
• Geographic patterns of European Y-DNA
• New paper on Spanish genetics (nuclear DNA but a poor paper)

 

The Late Bronze Age crisis in Britain, why?

Atlantic Bronze Age

There is a lengthy article today at BBC on what appears to be an economic crisis in Late Bronze Britain, between roughly 800 BCE and 500 BCE, when Iron begins showing up and a recovery seems to take place.

The article is lengthy but inconclusive. However I have my own ideas of why this decline: the Celtic invasion of Western Iberia, which, together with other parts of Atlantic Europe constituted an economic region since the beginnings of Megalithism beyond Portugal, in the fourth millenium BCE.

Hence, when we contemplate this crisis in Britain we are surely contemplating the last, extremely decadent, episode of an international civilization that had some three millennia of unwritten history.

Very briefly (dates may change slightly depending who you read):

• c. 4800 BCE the first dolmens (chamber tombs) appear in Southern Portugal, with their characteristic “collective” (clannic, sequential) burial style. This type of tomb defines the cultural phenomenon we can well call Domenic Megalithism.
• c. 3800 BCE Dolmenic Megalithism migrates to Armorica (Brittany, Mid-West France), where it acquires an elitist flavor peculiar of this country. 
• c. 3500-3000 BCE Dolmenic Megalithism expands through all Atlantic Europe, often hybridizing with other pre-existent of co-arriving traditions and in some cases at least signifying the first or almost first serious Neolithic, with the demographic implications this may have.
• Further expansion happens then into parts of Central Europe (Danubian area north of the Alps) and, later, into parts of Italy and North Africa.
• c. 2600 BCE two civilizations appear in Iberia: Los Millares and Zambujal (VNSP), the latter surely central to the Dolmenic Megalithic cultural area
• c. 2400 BCE Central and Northern European parts of this area (east of the North Sea-Rhine line) are lost to Indoeuropean culture (Corded Ware), however Western France and Belgium are consolidated into it (Artenac culture).
• For a whole millennium this ethno-cultural divide at the Rhine is stable. Bell Beaker (a secondary mercantile phenomenon) acts as a unifying force probably at between Westerners and Indoeuropeans. 
• Around 2000 BCE the center of Corded Ware is at Zambujal, which is a thriving civilization.
• c. 1800 BCE Los Millares is replaced by El Argar, a larger state probably, and one influenced by Mycenean Greece, specially in its last phase. 
• c. 1250 BCE Indoeuropean tribes (proto-Celts more or less) descend along the right bank of the Rhône river penetrating into Catalonia. It is the Urnfield culture expansion that has reflections in other parts of Europe (but does not affect other parts of the West yet).
• c. 1200 BCE Zambujal civilization ceases to exist, coincident with a silting of its 10 Km long “marine branch” or canal, which joined it to the Atlantic Ocean (tsunami?) At a similar date El Agar state collapses and its cities become independent (it seems: post-Argarian culture). 
• Atlantic Europe, not really anymore Megalithic in any intense sense of the word, retains its distinct personality within the Atlantic Bronze trade networks.
• c. 700 BCE Hallstatt-Urnfield Celts of NE Iberia invade the Northern Plateau and the Atlantic areas. It is likely, judging from the archaeological record, that at this time (or maybe a little earlier) the city of Tartessos was destroyed by the Phoenicians of Gadir (modern Cádiz). The Atlantic Bronze economic (and cultural) area is broken for good.

This last is what I think that caused the apparent economic crisis in Britain and not just the generic concept of technological advance of Iron: the destruction of their main economic partners in the South, with links to the Mediterranean (Sicily, Cyprus) and such. Only later, as new networks were established with continental (Celts of Belgica and Armorica) and naval (Phoenicians) partners, would Britain experience some economic recovery. But that would also be the seeds of their own Celtization a few centuries later (La Téne).