Ötzi the Iceman and the Sardinians

By Razib Khan | February 28, 2012 8:13 am

Well, the paper is finally out, New insights into the Tyrolean Iceman’s origin and phenotype as inferred by whole-genome sequencing. In case you don’t know, Ötzi the Iceman died 5,300 years ago in the alpine region bordering Austria and Italy. His seems to have been killed. And due to various coincidences his body was also very well preserved. This means that enough tissue remained that researchers have been able to amplify his DNA. And now they’ve sequenced it enough to the point where they can make some inferences about his phenotypic characteristics, and, his phylogenetic relationships to modern populations.

The guts of this paper will not be particularly surprising to close readers of this weblog. The guesses of some readers based on what the researchers hinted were correct: Ötzi seems to resemble mostly closely the people of Sardinia. This is rather interesting. One reason is prosaic. The HGDP sample used in the paper has many Northern Italians (from Bergamo). Why is it that Ötzi does not resemble the people from the region that he was indigenous to? (we know that he was indigenous because of the ratio of isotopes in his body) A more abstruse issue is that it is interesting that Sardinians have remained moored to their genetic past, enough so that a 5,300 year old individual clearly can exhibit affinities with them. The distinctiveness of Sardinians jumps out at you when you analyze genetic data sets. They were clearly set apart in L. L. Cavalli-Sforza’s The History and Geography of Human Genes, 20 years ago. One reason that Sardinians may be distinctive is that Sardinia is an isolated island. Islands experience reduced gene flow because they’re surrounded by water. And sure enough, Sardinians are especially similar to each other in relation to other European populations.

 

But Ötzi’s affinities reduce the strength of this particular dynamic as an explanation for Sardinian distinctiveness. The plot to the left is a PCA. It takes the genetic variation in the data set, and extracts out the largest independent components. PC 1 is the largest component, and PC 2 the second largest. The primary cline of genetic variation in Europe is North-South, with a secondary one going from West-East. This is evident in the plot, with PC 1 being North-South, and PC 2 being West-East. The “Europe S” cluster includes northern, southern, and Sicilian Italians. Now notice the position of Ötzi: he is closest to a large cluster of Sardinians. Interestingly there are also a few others. Who are they? I do not know because I do not have access to the supplements right now. The fact that the Sardinians are shifted closer to the continental populations than Ötzi is also striking. But totally intelligible: Sardinia has had some gene flow with other Mediterranean populations. This obviously post-dates Ötzi; Roman adventurers and Genoaese magnates could not be in his genealogy because Rome and Genoa did not exist 5,300 years ago. These data strongly point to the possibility of rather major genetic changes in continental Europe, and in particular Italy, since the Copper Age.  Juvenal complained that the “River Orantes has long flowed into the Tiber,” a reference to the prominence of easterners, Greek and non-Greek, in the city of Rome. The impact of this is not to be dismissed, but I do not think that it gets to the heart of this matter.

The second panel makes clear what I’m hinting at: Ötzi is actually closer to the “Middle Eastern” cluster than many Italians! In fact, more than most. Why? I suspect that rather than the Orantes, the Rhine and the Elbe have had more of an impact on the genetic character of Italians over the past ~5,000 years. Before Lombardy was Lombardy, named for a German tribe, it was Cisapline Gaul, after the Celts who had settled it. And before that? For that you have to ask where Indo-Europeans came from. I suspect the answer is that they came from the north, and therefore brought northern genes.


A Sardinian

And what of the Sardinians? I believe that the “islanders” of the Mediterranean are a relatively “pristine” snapshot of a particular moment in the history of the region. This is evident in Dienekes’ Dodecad Ancestry Project. Unlike their mainland cousins both the Sardinians and Cypriots tend to lack a “Northern European” component. Are the islanders in part descendants of the Paleolithic populations? In part. Sardinians carry a relatively high fraction of the U5 haplogroup, which has been associated with ancient hunter-gatherer remains. But it is also possible that the preponderant aspect of Sardinian ancestry derives from the first farmers to settle the Western Mediterranean.  I say this because the Iceman carried the G2a Y haplogroup, which has of late been strongly associated with very early Neolithic populations in Western Europe. And interestingly some scholars have discerned a pre-Indo-European substrate in Sardinian which suggests a connection to the Basque. I wouldn’t read too much into that, but these questions need to be explored, as Ötzi’s genetic nature makes Sardiniaology more critical to understanding the European past.

Image credit: Wikipedia

  • iron0037

    Thanks for taking the time to explain the principal component chart. I’ve always wondered what those things meant exactly :). I’m still not totally sure what “genetic variation in a data set” means exactly. I have a vague idea but it might be nice to create a simple, 10 marker example one day.

  • http://www.genomesunzipped.org J Pickrell

    Interestingly there are also a few others. Who are they? I do not know because I do not have access to the supplements right now.

    No mention of this in the supplement, though they might just be Sardinians from the PopRes data, rather than HGDP Sardinians? The paper is kind of ambiguous about who these people are:

    “In particular, the Iceman abuts the Italian samples originating from geographically isolated regions such as Sardinia (Fig. 3b). ”

    This makes it sound like it’s not *only* Sardinians, but is not particularly clear.

  • Patrick Wyman

    Really interesting stuff. Although it’s clearly well founded in the data, the genetic distinctiveness of Sardinians is pretty surprising to me: Sardinia has been more-or-less (at different times) bound into trans-Mediterranean networks of trade and communication for at least 2,500 years, if not longer, from the Carthaginians to today. I’m wondering what social and cultural factors have helped preserve that genetic distinctiveness.

  • j mct

    One of the tribes of the Sea Peoples that attacked Egypt around 1200 BC were called the Shardana, which many people equate with Sardinia, as they equate the Shekelesh with Sicily and the Peleset with Palestine, as in providing the names of these places. Which is, so the theory goes, where all these tribes eventually ended up after attacking Egypt. They were thought to have come out of Asia Minor, and left from a famine, like the Etruscans which Z writes about quite a bit. Would being from Asia Minor be ‘Middle Eastern’ in this context?

  • http://dispatchesfromturtleisland.blogspot.com ohwilleke

    “Unlike their mainland cousins both the Sardinians and Cypriots tend to lack a “Northern European” component.” Agree.

    “Are the islanders in part descendants of the Paleolithic populations? In part. Sardinians carry a relatively high fraction of the U5 haplogroup, which has been associated with ancient hunter-gatherer remains.” Agree.

    “But it is also possible that the preponderant aspect of Sardinian ancestry derives from the first farmers to settle the Western Mediterranean. I say this because the Iceman carried the G2a Y haplogroup, which has of late been strongly associated with very early Neolithic populations in Western Europe.” Agree.

    “And interestingly some scholars have discerned a pre-Indo-European substrate in Sardinian” Surely there must be such a substrate as quite a few words plausibly belonging to it have been identified, as we can bracket the arrival of Indo-European languages to Sardinia to a time period long after Sardinia was well populated, and one would expect a greater than usual substrate genetic distinctiveness to correspond to at least a par for the course or greater substrate linguistic influence.

    “which suggests a connection to the Basque.” I’m skeptical on this score, without dismissing it. The Gascons look more similar genetically to the Sardinians and Otzi than the Basque in terms of Y-DNA and lactose persistance and the failure of Sardians to share close relatives of a great many private Basque uniparental halogroups. There are a lot of loan words in Sardinian and given its fairly close proximity, Basque isn’t very predominant among them. Sardinian could conceivably have a Basque linguistic family substrate, but I would give greater weight to the argument that most of the similarities that are observed between Sardinian and Basque are due to a common substrate language associated with the Cardial Pottery Neolithic that pre-dates both Basque ethnogenesis and the Basque family of languages in Western Europe, as well as pre-dating the Indo-European languages of which Sardinian is a part.

    Alternately, most of the substrate influence could even be traceable all the way back to a Paleolithic substrate during which Sardinia was inhabited that is shared with Basque (either with or without an intermediate early Neolithic linguistic layer). Twenty-five of the twenty-seven pre-Latin substrate words Wikipedia identifies in Sardinian including Basque roots are technologically consistent with a hunting and gathering society. Two Basque roots (one for pig also shared by Basque with the Indo-European Illyrian language, and one for a year old lamb not apparently shared with other languages) have a strong association with a farming or herding mode of food production. Also the plants and animals in the substrate list are mostly the sort of animals that women in a gathering role might encounter rather than words for game animals that men might preserve, which would fit with the matriline genetics typically being more stable than the patriline genetics. “Womens words” may be more prone to presence in a subtrate than “men’s words” which one would expect to come from disproportionately from the superstate. The substrate words could be words that people like Otzi’s indigenous wives contributed to the language of their families.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    I’m wondering what social and cultural factors have helped preserve that genetic distinctiveness.

    perhaps malaria killed all the lowlanders who were cosmopolitan. modern sardinians may actually be descended from highlanders.

  • Simplicio

    Out of curiosity, is this the oldest human body we have this level of genetic data from? Can the same be done to bog bodies or Egyptian mummies or the like?

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    #7, no, neanderthals are older. and yes, it can be done on other bodies.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    This makes it sound like it’s not *only* Sardinians, but is not particularly clear.

    popres has random people from cities, right? i assume some sardinians and highland sicilians are in the mix. judging by g2a frequencies the ‘sardinian’ component is strongest in the mainland in alpine regions.

  • http://Finhall Brian Lovett

    I am interested by the mention of a possible Basque connection because latest information suggests that the Basques are mainly R1b (Western Atlantic Modal) relatively modern.

  • dave chamberlin

    It shouldn’t strike anyone as strange that a relic population should be found on an island. It has happened repeatedly in human history as well as animal history. New Guinea, Australia, Tasmania, and the Andaman Islands all have populations that show distinctive roots to early human migrations that have been wiped out or minimized on the nearby mainlands.

  • Palisto

    “It shouldn’t strike anyone as strange that a relic population should be found on an island. It has happened repeatedly in human history as well as animal history. New Guinea, Australia, Tasmania, and the Andaman Islands all have populations that show distinctive roots to early human migrations that have been wiped out or minimized on the nearby mainlands.”

    Yes, but it is interesting that apparently it happened in last 5300 years.

  • Simplicio

    @12 I’m not surprised that its an island so much as this particular island. I don’t know much about Sardinia, but neighboring Sicily has been a cross-roads for 3,000 years, with the Greeks, then Carthaginians then Romans, then Arabs then Normans then Italians ruling. I think there were some Vandals in there somewhere to. And during the Roman Republic period the population was supposedly mainly agricultural slaves brought in from abroad, so at least in some cases it wasn’t just a small overclass moving in and interbreeding with a stable native population.

    I would’ve thought Sardinia and other islands in the central Mediterranean would have similar histories and thus be “mutts” of other Mediterranean cultures.

  • Onur

    Simplicio,

    Sicily is adjacent to the Italian mainland, that is why it does not show island behavior in terms of demographic movements, so Sicilians are practically not islanders but Italian mainlanders. Also, Sardinia does not neighbor Sicily, the only neighbor of Sardinia is Corsica. Unfortunately, there is currently no detailed research on Corsican autosomal genetics, but the most detailed extant autosomal study on Corsicans (Vona et al.) shows Corsicans to be genetically closest to Sardinians and, like Sardinians, pretty far from Italian mainlanders (including Sicilians) and French mainlanders.

  • Eurologist

    I can’t take this talk of “relics” and “replacement” seriously. Both Ötzi and Corsicans/ Sardinians are mainly typical Europeans, autosomally. They just lack the Northern component that has diffused into southern Europe from IE to historic times, and appear to lack as much West Asian as Italy and Greece and a portion of the Balkans have today. I believe there was a pretty steep East-West gradient of West Asian just after the beginning of the neolithic, and that has diffused a bit more, since then, as would be expected.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    They just lack the Northern component that has diffused into southern Europe from IE to historic times, and appear to lack as much West Asian as Italy and Greece and a portion of the Balkans have today.

    that is atypical.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    Sicily is adjacent to the Italian mainland, that is why it does not show island behavior in terms of demographic movements, so Sicilians are practically not islanders but Italian mainlanders.

    this is false. don’t make stuff up on the fly. the distinction between sicily and southern italy is real, though the chasm is not analogous to the sardinian vs. mainland one. (you will not respond with a long comment explaining yourself at length, i know enough about sicily and its peculiar history to know you’re making assertions post hoc).

  • Onur

    this is false. don’t make stuff up on the fly. the distinction between sicily and southern italy is real, though the chasm is not analogous to the sardinian vs. mainland one. (you will not respond with a long comment explaining yourself at length, i know enough about sicily and its peculiar history to know you’re making assertions post hoc).

    I am not talking about history but genetics. History tells us that South Italy and Sicily were many times invaded and ruled by different groups in the past, but genetics tells us that they have not differentiated the genetics of Sicily and South Italy in a significant way. Genetically South Italians and Sicilians are virtually identical. The sole difference between them is the presence of a bit more African admixture in Sicilians (that is probably recent and connected with the Muslim Arab/Berber invasions).

  • Onur

    Also, by “demographic movements” I was referring to the demographic movements as a whole, not just foreign invasions. Only genetics can inform us about the demographic movements as a whole (albeit in a crude manner).

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    #19, be more precise in the future. i think you over-read the genetic argument, but it is defensible. in contrast, the straits of messina have not been trivial culturally.

  • Onur

    Well, when it comes to demographic movements, I try to use genetics and historical information concurrently whenever available, but my priority is, quite understandably, on genetics.

    As for the Strait of Messina, the Calabro-Sicilian language is spoken on both sides of the strait (not in itself a strong argument for a strong gene flow, but it complements the genetic evidence).

  • Roberto Congiu

    I think that it makes more sense to see this in the perspective of human migration.
    Sardinia was inhabited during the ice age, when sea levels were lower, and you could probably walk to the island from the mainland through Corsica. The end of the last ice age left Sardinia actually isolated. It is believed that the people who lived in Europe in that period had a generic marker (Haplogroup I, see http://en.wikipedia.org/wiki/Haplogroup_I_(Y-DNA) ) but subsequent migration from the east relegated this group to some more remote places (the balkans, scandinavia, and Sardinia). Most people in Europe in fact belong to the Haplogroup R.
    It is indeed conceivable that simply Otzi was from the same people who settled Sardinia and Corsica from central Itali, or shared an ancestor with them.

  • http://dispatchesfromturtleisland.blogspot.com ohwilleke

    “judging by g2a frequencies the ‘sardinian’ component is strongest in the mainland in alpine regions.”

    Immediately pre-Italo-Celtic that would have been a Rhaetic-Etruscan linguistic area and Tuscany was Etruscan before it was Latin. There are disputed about where the Rhaetic-Etruscan people cam from among the classical authors, but at least view was that they were migrants/relic populations who arrived there from Southern France before they were displaced by the Celtic Gauls.

  • dave chamberlin

    Before this thread slides into history I would like to make a few comments on Otzi that have nothing to do with genetics, yet. We have considerable evidence on Otzi the man that paints a picture of him as an incredibly competent human being. He approaches the competence of one of those rediculous Jean Auel characters whom are near perfect in every single way. He wasn’t just found with a copper axe one thousand years before the supposed beginning of the copper age, he was found with high levels of arsenic in his blood meaning he was in all likelyhood a coppersmith himself. I won’t go into the long list of items he had with him but it is a clear indication of his very high competence in a number of skills. This won’t mean much yet but it will down the road as genetics advances to identify incredibly complex genetic patterns that signify high intellegence. For here we have the complete genome not just of a 5300 year old human but a damned intelligent one as well. As they say in the news business this is a story with legs. Recently there has been found on Otzi the blood of two other individuals meaning he went down successfully fighting. That the arrow that killed him was removed but that his valuable copper axe was left is weird and has left some to speculate his murderer did not want to be discovered as Otzi still had powerful and dangerous friends.

  • Bobby Boone

    The picture at the bottom of the article is Elisabetta Canalis and she was born on September 12, 1978, in Sassari, Italy. Although Elizabett is quite pretty, a more appropriate picture of a Sardinian woman might be http://toporagno.deviantart.com/art/Sardinian-women-48485507.

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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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