Bronze Age

A new study by Remco Bouckaert and colleagues attempts to place the origin of Indo-European languages by using an epidemiological population model, essentially plotting the "spread" of languages from a common source [1].

To test these two hypotheses, we adapted and extended a Bayesian phylogeographic inference framework developed to investigate the origin of virus outbreaks from molecular sequence data (13, 14). We used this approach to analyze a data set of basic vocabulary terms and geographic range assignments for 103 ancient and contemporary Indo-European languages (15–17). Following previous work that applied Bayesian phylogenetic methods to linguistic data (1–3), we modeled language evolution as the gain and loss of “cognates” (homologous words) through time (18–20). We combined phylogenetic inference with a relaxed random walk (RRW) (14) model of continuous spatial diffusion along the branches of an unknown, yet estimable, phylogeny to jointly infer the Indo-European language phylogeny and the most probable geographic ranges at the root and internal nodes. This phylogeographic approach treats language location as a continuous vector (longitude and latitude) that evolves through time along the branches of a tree and seeks to infer ancestral locations at internal nodes on the tree while simultaneously accounting for uncertainty in the tree.

Diffusion models applied to spatial data tend to place the origin at the center of the present geographic distribution. That's just the simplest way to explain any geographic distribution under the diffusion model, which assumes that people act like random particles.

By contrast, Phylogeographic models tend to place the origin near the point with maximal clade distance. One ancient Anatolian language, Hittite, is attested in written records and according to the phylogenetic analysis is an outgroup to other, more recent Indo-European languages. Armenian, Greek, and Albanian also belong to relatively deep clades, and they geographically flank Anatolia in different directions.

So in this case, both diffusion and phylogenetic approaches point toward Anatolia as the most parsimonious origin.

Additionally, when the centers of diversification of the major Indo-European families are considered (e.g., Celtic, Romance, and Indo-Aryan), the geographic center of their distribution is Anatolia. Figure 2 of the paper illustrates the geographic ranges estimated as origins for the different clades within Indo-European:

Looking at the picture, Anatolia looks like ground zero for the viral spread of Indo-European languages.

OK, so the logic of the model pretty much inevitably leads to the conclusion. Anatolia is at the geographic center of the early Indo-European families, and is geographically central to the earliest branches of the language tree. But should we believe it? Languages, after all, don't spread exactly like viruses. And viruses don't spread by diffusion much of the time -- if they did, the movie Contagion would have had a lot more boring plot.

I have no strong reason to be skeptical of the main conclusion, that the first Indo-European language may have originated in Anatolia. But I do note that it's strongly influenced by the evidence we happen to have about ancient languages. If we had a stronger record of the ancient languages of Central Asia, who knows what we might find? Tocharian, in the Tarim Basin of western China, was also a relatively deep clade in the Indo-European phylogeny, spoken within the last 2000 years. Could there have been others?

Also, Razib Khan points out some issues with the dates that the model attributes to branch points in the tree: "There are more things in prehistory than are dreamt of in our urheimat".

Bouckaert and colleagues set up an opposition between two hypotheses for the origin of the Indo-European. The first derives the family from Anatolia more than 8000 years ago, possibly shortly after the origin of agriculture in the Fertile Crescent. This is more or less the Colin Renfrew model of Indo-European, which posits that the language family was able to spread due to the population expansion of agriculturalists. In this model, the first Neolithic peoples of Europe should have been Indo-European speakers.

The alternate hypothesis is that Indo-European originated on the steppes of Central Asia and Eastern Europe. This is more or less the Marija Birute Gimbutas model, where early steppe peoples spread westward carrying Indo-European with them. Some linguists and archaeologists have strongly favored this model because of the words reconstructed as part of the proto-Indo-European language, which include many technological and ecological elements that would have been familiar to steppe pastoralists of 4500-6000 years ago.

This seems like a clear dichotomy -- either Indo-European was early and spread with agriculture, or it was later and spread into regions already agricultural. In the first case, the language spread was mostly caused by demographic growth, in the latter case, other mechanisms such as elite dominance and conquest may have played more important roles. So it is interesting that this paper, after concluding an early Anatolian origin was supported by the data, actually argues for a much softer, intermediate position:

Despite support for an Anatolian Indo-European origin, we think it unlikely that agriculture serves as the sole driver of language expansion on the continent. The five major Indo-European subfamilies—Celtic, Germanic, Italic, Balto-Slavic, and Indo-Iranian—all emerged as distinct lineages between 4000 and 6000 years ago (Fig. 2 and fig. S1), contemporaneous with a number of later cultural expansions evident in the archaeological record, including the Kurgan expansion (5–7). Our inferred tree also shows that within each subfamily, the languages we sampled began to diversify between 2000 and 4500 years ago, well after the agricultural expansion had run its course.

I think this is the most important passage of the paper. Reading between the lines, it says that the origination point for Indo-European languages simply may not address the archaeological record. What if Indo-European got its start in Anatolia 10,000 years ago, but many of the modern branches of Indo-European within Europe -- Celtic, Italic, Germanic -- all moved into Europe in several separate waves, starting less than 6000 years ago from the Pontic Steppe? We have pretty good genetic evidence now that the first farmers in Europe were not very much like recent Europeans. We need later migrations into Europe from elsewhere to explain the genetic record, and the archaeology (and later, history) provides plenty of reasons to think that later migrations were important.

So, there we are. Even though the present study supports an early, Anatolian origin for Indo-European, other evidence rejects the simple Colin Renfrew model. The present Indo-European families did not reach their present geographic distributions with the first agriculturalists. That means we need to look at more complex intermediate steps to explain how current and historic Indo-European languages got to their attested locations. The steppic model might well explain the spread of languages between 6000 and 4000 years ago, even if they shared earlier ancestors that fit the Anatolian model.

References

There are many stories from my travels last summer that I haven't yet told here. I've been thinking that I need to get them written down, so that I'll have more time to write about my upcoming travel this summer. I have copious notes about the time in Denisova itself, and I'll be returning to those. In the meantime I'd like to share some other experiences. Here I want to turn to the subject of kurgans.

An Altai landscape

I went to the Altai for the Paleolithic, because Neandertals and Denisovans lived in the area for tens of thousands of years. But the area is even better known for much later remains, from the Neolithic and Bronze Age up to the Iron Age. A succession of ancient cultures lived in this region, at the crossroads of China, the Tibetan Plateau, Mongolia, and the Russian and Kazakh steppes. Most of the prehistoric peoples of the Altai were pastoralists, nomads who depended on herding cattle, sheep, and horses. Keeping their wealth and food sources on the hoof instead of in the ground, they moved between summer and winter foraging grounds for their herds. They also relied heavily on hunting the rich game in the region, notably red deer.

Denisova Cave itself was used by these early herders. People kept sheep fenced in the cave, every so often burning the accumulated manure and bedding and imperfectly sweeping the ashes. The topmost levels of the archaeological deposits are densely stratified layers of burned ash and debris, left across thousands of years.

Denisova archaeological layers dating to the Holocene. The thin contrasting layers here at the top of the deposit include Neolithic and later burned sheep debris.

Many Altayan people today live in towns, made of Russian-style wood houses. The economy is still heavily based on cattle, and additionally there are large red deer operations. Horses are even today a large part of the culture, and every town seems to have its stadium for the local equivalent of polo. People of traditional Altayan ancestry are a minority even in the Altai Republic, with other nationalities and ethnic Russians making up more than half the population. Altayan houses in the towns are quite distinctive because many of them have a round "summer house" next to them. These mirror the portable yurts that were the traditional summer domiciles of the Altai peoples, giving them a chance to get out of their winter houses and sleep beneath a round roof during the warmer part of the year.

An Altai town. A few of the foreground houses have round "summer houses" in their yards.

Among the earliest cattle herders in the area were people of the Afanasievo culture. These people moved into the Altai area around 4800 years ago and persisted for nearly 1000 years. They lived before metallurgy really became very common in this area, although metal objects are sometimes found in their graves. Like other nomads, their residence sites were relatively ephemeral and their burial sites give us essential information not only about their social lives but also about their economy and subsistence practices.

An Afanasievo kurgan.

Mound-like burial sites in this part of the world are called kurgans, and often involve both stones and earthwork. Some Afanasievo kurgans are quite distinctive, with a round circle of upright, flat stones. Sometimes these are tall, like the petals of a rocky sunflower. Sometimes, they are barely higher than the mound within, almost forming a curb around its edge.

Detail of stones surrounding an Afanasievo kurgan.

I've driven through a lot of Kansas cattle pasture, and the texture of the land here was familiar. Here in Wisconsin, we have some extensive Mississipian and earlier moundworks, but many have been plowed and often destroyed, after less than a thousand years. In the Altai, running across 4000-year-old stone formations, basically undisturbed on the pasture surface -- that was pretty cool.

Detail of an Afanasievo kurgan, horses grazing in background.

Of course, "undisturbed" is a relative concept. Most of the kurgans have undergone some amount of grave-robbing. For the elaborate later mounds, the plundering often really changed their profile. The Afanasievo kurgans, with their relatively flat shape and haphazard stone paving, don't make disruptions quite as evident.

Another Afanasievo kurgan.

Many archaeologists believe the Afanasievo people to have been speakers of an early Indo-European language. The kurgans and stylistic elements of Afanasievo culture are similar to those found later much further to the west, across the Russian steppe. Possibly the Afanasievo people were connected to the Tocharians, whose Indo-European language is attested by inscriptions from the far west of China before 1000 BC.

By far the more famous kurgan-building people were carriers of the Pazyryk culture. These people lived much later than Afanasievo in the area, within the first millennium BC. They used bronze and iron, and lived at the eastern end of a cultural complex that extended across the Russian plain to the area north of the Black Sea. The Greeks contacted the westernmost of these people, the Scythians, and the high mobility and extensive trade through Central Asia certainly indicates a cultural continuity if not identity from east to west across this range.

The Pazyryk kurgans were huge mounds, made up of volleyball-sized stones. We clambered across a couple of these near a main road in the middle Altai.

A Pazyryk kurgan.

Kurgans were mounded atop a timber-roofed grave chamber, which included one or more bodies and elaborate grave goods. One kurgan produced a wheeled chariot with horses, giving some impression as to their scale. The kurgans we examined had been excavated by archaeologists during the 1920's, and both now have a large hole in the middle where the grave had been. One had a large larch tree growing up out of the center:

Strange place for a tree.

Rainwater seeped into the Pazyryk kurgans, deep into the tombs themselves, and there the water froze into ice. Many of the mounds were large enough to keep ice frozen year-round. Although most were plundered by ancient graverobbers, archaeologists found a few spectacular instances where textiles and other perishable materials were preserved.

A sample of ancient fabric, at the museum of the Archaeology Institute in Novosibirsk

You won't be surprised to know that, for me, the most interesting discoveries from the Pazyryk kurgans were the physical remains of the people themselves. The extensive effort toward building the mounds, and valuables included in the burials, signify that the kurgan bodies were some of the highest-status individuals in Pazyryk society. High-status people were not exclusively high-ranking males or warriors, they sometimes were females.

Since 1993, the most famous of the kurgan discoveries has been the mummified woman known as the "Ice Maiden". This mummy was found by Natalia Polosnak, as she excavated a kurgan on the Ukok Plateau in the border area between Russia and China. Dating to the fifth century BC, the mummy was the subject of a massive effort to defrost and transport her body by helicopter for study, which was the subject of a documentary.

The Ice Maiden in the museum in Novosibirsk

Her skin provides the earliest known evidence of tattooing anywhere in the world. Probably tattoos are much more ancient than this -- personally, I'm betting that both Neandertals and Middle Stone Age Africans were using mineral pigments and charcoal in tattoos. But the few instances in which we have earlier skin preserved, such as the ancient Egyptians, simply were not tattooing cultures.

The Ice Maiden's tattoo

In the case of the Ice Maiden, her tattoo is a beautiful example of the elaborately antlered red deer, so typical of Pazyryk decorative objects. For example, here is a bronze red deer bangle:

A bronze red deer

That red deer motif is really common in this area of the world, found as portable objects, as sometimes elaborately-carved inscriptions on stelae, and on fabrics. This iconography is much older than the Pazyryk culture, found well into the second millennium BC in Mongolia. There, carved stelae called "deer stones" appear at a particular type of burial site. These stones seem to represent stylized warrior figures, equipped sometimes with belts and weapons, for which the deer (and sometimes other animal) inscriptions may represent tattoos.

Deer stones do occur in the Altai, but I didn't run across any of them during my time there. I did see many simpler stelae, sometimes by themselves and sometimes in groups. These burial markers can be found across thousands of years of different cultures. Most of the ones are probably attributable to more recent peoples in the area within the last 2000 years.

A second Pazyryk mummy lay next to the Ice Maiden in the museum. This mummy, a man, also bears a tattoo: a canine of some sort, if I remember correctly. The mummy has long, ashen-blond hair. The hair of mummies is sometimes misleading, beacuse the pigments can be affected by their burial. But the Tarim Basin mummies from China, dating to more than a thousand years before this man, also had light, sometimes reddish hair. It will be fascinating to learn more about the genetics of these ancient people, to see the ways they are connected to later populations in the region and elsewhere.

The male mummy

Some truly recent grave sites in the area can also carry great anthropological interest. For example, the Pazyryk kurgans we saw weren't alone. Next to them, the nearby town had put a modern cemetery.

The local cemetery

A close look at the markers in this cemetery shows that they often have pictures of the deceased.

The local cemetery

Surprisingly, many of them include inscriptions in Korean. Southern Siberia was a resettlement area for many Korean nationalists, who left Korea during the Japanese occupation.

It is fascinating that this area was central to ancient trade and communication routes, but today seems so removed from the main arteries of international transit. I've never been anywhere with so few jets passing far overhead, and no major highways or rail routes pass through the area. Yet, when we look at the composition of the population, there are people who immigrated from far-flung areas to this corner of the world. The Altai draws people into it today, just as it has done for thousands of years.