The figure above is from The genomic history of the Iberian Peninsula over the past 8000 years. If you had seen something like this five years ago, you’d be gobsmacked. But today this is not atypical, especially in light of the fact that Spain seems to harbor many good sites in relation to the preservation of ancient DNA. In the figure above you see an excellent representation of the different streams of ancestry and settlement within Spain over the last 8,000 years. You can conclude from it, for example, that only a small proportion of the ancestry of modern Spaniards derives from people who were residents of the peninsula during the Pleistocene. Similarly, you can also conclude that a minority, though non-trivial, proportion of the ancestry of modern-day Spaniards derives from people who arrived during Classical Antiquity and the Moorish period.
David Reich submits Five Corrections to The New York Times.
As you know, in the fact-checking process I was sent more than 100 statements of which a very high proportion (more than half) were incorrect. For example, as I mentioned to you in my letter of January 7, 20 of 49 statements presented to me for review on January 2 were incorrect, and 27 of the 36 statements presented to me for review on January 5 were incorrect. The high rate of errors was concerning as it suggested that the narrative based on them might not be supported by a solid set of facts. While a substantial number of these incorrect statements were removed through your fact-checking process, some errors got through, and I am therefore now requesting formal corrections of the following 5 errors that meaningfully affect the article, so it is important to set the record straight on them. (I have also identified additional errors, but those are for the most part smaller, so I am not requesting corrections in those cases.)
One of the frustrating aspects of The New York Magazine piece is that I have read probably read most of the Reich lab’s papers over the last 5 years or so (perhaps earlier), so I knew which factual points were false or exaggerations, but I didn’t want to highlight them incessantly because people would get lost in the muddle of detail. For example, in relation to this assertion:
About 5,000 years ago, a “relatively sudden” mass migration of nomadic herders from the east — the steppes of eastern Ukraine and southern Russia — swept in and almost entirely replaced the continent’s existing communities of hunter-gatherers and early farmers.
The figure from Haak et al. 2015 immediately came to mind. It literally rejects the characterization in a quick and simple figure (the population that purportedly “entirely replaced” is green). Obviously, the figure does not show what the piece claims Reich believes, and it is not credible that he would assert something that is refuted by the papers his own lab publishes. If you had read this area you would know all this, but even population geneticists who are not immersed in the human ancient DNA literature likely would not pick up on this. The sample size objection was in a similar class.
Here’s what I’m going to leave you if you are an outsider: if the author misrepresents so many details, how much should you trust them in broad strokes?
The piece was not reportage. It was rhetoric. Sophistry.
Update: David Reich asks for five corrections to the piece in The New York Times Magazine piece.
Didn’t mean to post so much about that crappy piece in The New York Tines Magazine. But there’s so much tendentious crap in it. That being said, I am probably not going to post much more on this, because David Reich’s response is up:
Letter in response to Jan. 17 article in The New York Times
January 19, 2019
To the Editor:
Gideon Lewis-Kraus (Jan. 17) profiles the nascent field of ancient DNA, which in the last few years has contributed to a transformation in our understanding of the deep human past. His article touches on important issues that we, as a field, have yet to deal with fully: including how to handle ancient remains ethically and in a way that preserves them for future generations; how geneticists and archaeologists can work in equal partnerships that reflect true respect for the insights of different disciplines; and how ancient DNA technology, which at present is applied efficiently only in large labs, can be made accessible to a wider group of scholars.
But Lewis-Kraus misunderstands several basic issues. First, he suggests that competition to publish is so extreme that standards become relaxed. As evidence, he cites a paper by my lab that was accepted on appeal after initial rejection, and another that was reviewed rapidly. In fact, mechanisms for appeal and expedited review when journals feel they are warranted are signs of healthy science, and both processes were carried out rigorously.
Second, he contends that ancient DNA specialists favor simplistic and sweeping claims. As evidence, he suggests that in 2015 I argued that the population of Europe was “almost entirely” replaced by people from the Eastern European Steppe. On the contrary, the paper he references and indeed my whole body of work argues for complex mixture, not simple replacement. Lewis-Kraus also suggests that I claimed that our first study of the people of the Pacific island chain of Vanuatu “conclusively demonstrated” no Papuan ancestry. But the paper in question was crystal-clear that these people could have had some Papuan ancestry – and indeed, to support his claim, Lewis-Kraus could only cite his own notes from an interview I gave him long after I had published a second paper proving that there was indeed a small proportion of Papuan ancestry.
Lewis-Kraus also suggests that I use small sample sizes to make unjustifiable sweeping claims. In fact, small sample sizes can be definitive when they yield results that are incompatible with prevailing theories, as when my colleagues and I described two samples that proved the existence of the Denisovans, a previously undocumented archaic human population. In my papers, I am careful to only make claims that can be supported by the data I have. In small-sample size studies, I emphasize that more samples are needed to flesh out the details of the initial findings. A major focus of my lab is generating the large data sets needed to do this.
Lewis-Kraus’s critiques are based on incomplete facts and largely anonymous sources whose motivations are impossible to assess. Curiously, he did not ask me about the great majority of his concerns. Had he done so, the evidence underlying his thesis that my work is “indistinguishable from the racialized notions of the swashbuckling imperial era” would have fallen apart. The truth, and the main theme of my 2018 book Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past, is exactly the opposite – namely, that ancient DNA findings have rendered racist and colonialist narratives untenable by showing that no human population is “pure” or unmixed. It is incumbent on scientists to avoid advocating for simplistic theories, and instead to pay attention to all available facts and come to nuanced conclusions. The same holds true for journalists reporting on science.
Harvard Medical School and the Howard Hughes Medical Institute, Boston, Massachusetts
There is a very long piece in The New York Times Magazine, Is Ancient DNA Research Revealing New Truths — or Falling Into Old Traps?. It’s the talk of DNA-Twitter for obvious reasons. The very fact that you have a long piece in The New York Times Magazine on this topic means that David Reich is almost certainly going to made into something of a villain. The reason I say this is that these sort of narratives pitched to a general audience have to exhibit novelistic drama and plot, and so there are “spots” preexistent for both antagonists and protagonists. If the writer doesn’t create that narrative, the piece would probably never see the light of day. Who would read it?
So before the first pixel loaded, I knew:
1) David Reich was going to be the antagonist
2) And indigenous people, along with supporting archaeologists were going to be protagonists
This does not speak to whether this is “true” or not. It is simply how it was going to work out if the piece was ever going to be published because those are the elements of a story that would appeal to readers of The New York Times. This is a product strongly shaped by consumer demand.
One thing I want to address is a critique, expressed by some academics in the piece, that researchers in ancient DNA do not have the number of samples to make the generalizations that they make. This seems reasonable on the face of it, but one thing you have to consider is that when you obtain an individual’s DNA you get a window onto their whole pedigree. A single individual is actually a pedigree if you have its genome. A genome provides an enormous amount of data. It is an endpoint of a historical process of sexual reproduction that extends back many generations. This is how you can use a single whole genome to infer whole population histories. One of the consequences of humans being “evolutionarily young” is that we all bear the stamp of some common processes and events.
From a naive perspective, you can say things like “how do you know this person is related to other people in the area?” And taken in the aggregate there are cases where unrepresentative individuals will yield results that mislead researchers. But on the whole over the last decade or so these groups have developed certain intuitions and guidelines, and have been rather good at making inferences based on a few data rich individuals. They make mistakes. But most objections about the nature of the data are really unfounded (albeit, widespread).
Many of the aspects of the piece do ring true. There are only a few huge laboratories in the ancient DNA space which tend to hoover up samples and collaborators. I have a suspicion I know who this is: ‘One geneticist compared competing with the big labs to battling an entire navy ‘with a little dinghy, armed with a small knife.”‘ For Holocene period analysis, the two big players are the Reich group and that of Eske Willerslev (Johannes Krause is going to make a splash with Late Antiquity). Though Eske’s group is mentioned offhand, it is curious that he himself is not mentioned at all.
In many ways, Eske is a much more colorful figure than Reich, and many of the issues applicable to the work of the latter and his relationships with indigenous peoples and archaeologists apply to the former. But in the United States David Reich is a brand name to the general public that Eske is not, and there can be only one devil in the underworld. But from a narrative perspective, Reich presents less raw material. He is a soft-spoken and delicately built vegetarian computational biologist. Eske Willerslev is the scion of Vikings whose background is in fieldwork as an anthropologist. His autobiography, written in Danish, is apparently very colorful!
Over the last few days I’ve been looking at genetic data related to the Middle East, and as part of that process, I added some Ethiopian samples (in particular, Beta Israel). Which has brought me to thinking about the issue of the origins of the Ethiopians. In 2012 Pagani et al. published a paper which concluded modern Ethiopian peoples by and large emerged out of an admixture event that occurred around ~3,000 years ago. The Sub-Saharan African ancestors of Ethiopians seem to be most similar to the peoples of Sudan. The dating of this admixture is really recent historically. In fact Homer mentions Ethiopians, which suggests that people in the Near East and Eastern Mediterranean may have had some awareness of various populations in this region while the mixing between different ancestral streams was occurring at that very moment (recall most admixture datings pick up the last signals, not earlier ones).
Pagani and those working with him published follow-up paper which indicated that the Eurasian ancestry in Ethiopians is most similar to that in Egypt and the Levant, and not to that in southern Arabia (in particular, Yemen). Their method broke down “tracts” of Eurasian ancestry, and compared affinities segment-by-segment. This is curious because genome-wide methods (e.g., Admixture, Treemix) always indicate that the Eurasian affinity of Ethiopians are with Yemenis. Seeing as how Yemen is literally across the Red Sea, this is reasonable. Pagani et al. suggest that the Yemeni affinity is due to Ethiopian gene-flow into Yemen (the two regions are historically bound together through conquests, etc.).
To make a long story short, I’m not totally convinced by this analysis. Over the past few years, we have more information on the genesis of the East African genetic landscape. First, an ancient genome from Mota in the Ethiopian highlands dated to 4,500 years ago did not have Eurasian admixture. This confirms Pagani et al.’s supposition of a relatively recent admixture event in the Ethiopian highlands. Skoglund et al. 2017 reported on ancient DNA from a Tanzanian pastoralist dating to 3,100 years before the present. This individual’s Eurasian ancestry (~40 percent) is similar to that of pre-pottery Neolithic Levantines. In other words, they lack genetic affinity with farmers from the eastern regions of the Near East. In contrast, Skoglund et al. report that modern Somalis have about ~15 percent of their ancestry from these eastern (“Iranian”) farmers, as well as the Levantine ancestry.
The data seem to be pointing to the fact that the emergence of the genetic patterns in the “Horn of Africa” were likely complex, and occurred through multiple waves of interaction and migration. As the map above makes clears there are two major branches of the Afro-Asiatic language families present in Ethiopia and Somalia, Semitic and Cushitic. The presence of Arabic to the north and west is a relatively recent phenomenon. The Nubian languages were Nilo-Saharan, while the language of ancient Egypt was a separate branch of Afro-Asiatic from Cushitic and Semitic.
The ancient languages of Yemen are part of the same “South Semitic” family as the Ethiopian Semitic languages. Though this may have been cultural diffusion, it does suggest that the genetic signal of connection points to a real phenomenon in terms of migration. Yemenite Jews and many Yemeni non-Jews do not have very much Sub-Saharan African ancestry, suggesting to me that before the rise of Islam most of the gene-flow was from southern Arabia to Ethiopia. A dynamic which reversed with Islam, as a substantial minority of the ancestry of most Yemenis is now Sub-Saharan African.
This does not account for the Cushitic languages. It seems that the Savanna Pastoral Neolithic cultures, of whom the Tanzanian pastoralist in Skoglund et al. was a representative, spoke Cushitic languages. This would mean that the languages of the largest number of Ethiopians, and that of Somalia, is that of the earliest Eurasian migrants into much of Sub-Saharan East Africa. The “Iranian farmer” ancestry in modern Somalis indicates long-term contacts with later migrants, possibly Semitic-speaking populations. Only in the highlands of northern Ethiopia did Semitic languages overtake Cushitic ones. Meanwhile in much of East Africa Cushitic gave way to other languages, often from the Nilo-Saharan family.
There is the broader question of where Afro-Asiatic languages come from. The diversity of languages in Ethiopia have suggested to some that one should look in Africa. I think that Ethiopia’s diversity is like that of the Caucasus: an artifact of rugged mountainous terrain. Rather, the existence of a very distinct Egyptian language 5,000 years ago quite different from contemporaneous Semitic Akkadian, suggests that the roots of this language family are quite old. I suspect that Semitic was intrusive to Ethiopia from Yemen, and that Cushitic became dominant in the period after the Mota individual flourished, and probably arrived from the north. Both the affinities with Levant populations and Yemenis make sense in this light. Much stronger genome-wide affinities with Yemenis could be because of the Ethiopian admixture into Yemen at some basal level quite early in history.
Update: The always well informed “Lank” leaves this comment:
Several problems with this. The Somali model you are referring to models them as a mixture of the 3100 ybp Tanzanian pastoralist, modern Sudanese Dinka, and Iranian farmers. This is unrealistic for several reasons, which could explain the strange 15% Iran-related ancestry that would imply very significant Semitic ancestry in Somalis, since early Semites themselves were mostly not of Iran-related ancestry as far as we know.
Analyses of the 3100 YBP Tanzanian pastoralist’s raw data, e.g. using David’s G25, reveal her to be very similar to Somalis. She can actually be modeled as ~90% Somali, with admixture related to East/South African hunter-gatherers. This is plausible as hunter-gatherers were the natives of the Rift Valley, and mixed with the proto-South Cushites of the Savannah Pastoralist culture represented by this sample. We see this in modern South Cushitic Tanzanian Iraqw (and ‘Nilo-Hamites’ like the Datog, of mostly Cushitic ancestry and cultural affinity) as well, who have very significant mtDNA related to the native hunter-gatherers of the Rift Valley. Much more than the currently more numerous Bantus, who have arrived more recently, South Cushites have mixed with hunter-gatherers. So using admixed early South Cushites like the Tanzanian to model Somalis, who despite being a modern population are actually fairly similar to pre-proto-South Cushites, may be what results in the strange model. Other analyses show that Iran/CHG-related ancestry in Somalis, if present, is very low. The raw data is out there if you want to try the models yourself.
Mota is a highly interesting sample, but not relevant for dating the admixture in early Cushites. He was found in remote southwestern Ethiopia, not really a stronghold of Cushites even today. The African component in Somalis (and most of the SSA in Cushitic/Semitic Ethiopians) is more closely related to the Sudanese, not the Omotic-speaking groups, who we now know tend to have high levels of ancestry related to Mota (other than Omotic groups like the Wolayta living closer to Cushitic/Semitic groups).
The recent 3 kya admixture model for the majority of the Eurasian admixture in Cushitic/Semitic populations does not hold up to scrutiny. The predominant overall ancestry as well as Eurasian admixture levels of the Tanzanian 3100 YBP sample is actually very similar to Somalis, with some local admixture. Finding this sample resembling modern Cushites all the way in Tanzania supports that its admixture traces back to the very earliest Cushites, who are certainly older than 3000 years.
A massive new ancient DNA preprint just dropped, The population history of northeastern Siberia since the Pleistocene:
…Here, we report 34 ancient genome sequences, including two from fragmented milk teeth found at the ~31.6 thousand-year-old (kya) Yana RHS site, the earliest and northernmost Pleistocene human remains found. These genomes reveal complex patterns of past population admixture and replacement events throughout northeastern Siberia, with evidence for at least three large-scale human migrations into the region. The first inhabitants, a previously unknown population of “Ancient North Siberians” (ANS), represented by Yana RHS, diverged ~38 kya from Western Eurasians, soon after the latter split from East Asians. Between 20 and 11 kya, the ANS population was largely replaced by peoples with ancestry from East Asia, giving rise to ancestral Native Americans and “Ancient Paleosiberians” (AP), represented by a 9.8 kya skeleton from Kolyma River. AP are closely related to the Siberian ancestors of Native Americans, and ancestral to contemporary communities such as Koryaks and Itelmen. Paleoclimatic modelling shows evidence for a refuge during the last glacial maximum (LGM) in southeastern Beringia, suggesting Beringia as a possible location for the admixture forming both ancestral Native Americans and AP. Between 11 and 4 kya, AP were in turn largely replaced by another group of peoples with ancestry from East Asia, the “Neosiberians” from which many contemporary Siberians derive. We detect additional gene flow events in both directions across the Bering Strait during this time, influencing the genetic composition of Inuit, as well as Na Dene-speaking Northern Native Americans, whose Siberian-related ancestry components is closely related to AP. Our analyses reveal that the population history of northeastern Siberia was highly dynamic, starting in the Late Pleistocene and continuing well into the Late Holocene. The pattern observed in northeastern Siberia, with earlier, once widespread populations being replaced by distinct peoples, seems to have taken place across northern Eurasia, as far west as Scandinavia.
The preprint is very interesting and thorough, and the supplements are well over 100 pages. I read the genetics and linguistics portions. They make for some deep reading, and I really regret making fun of Iosif Lazaridis’ fondness for acronyms now.
I will make some cursory and general observations. First, the authors got really high coverage (so high quality) genomes from the Yana RS site. Notice that they’re doing more data-intense analytic methods. Second, they did not find any population with the affinities to Australo-Melanesian that several research groups have found among some Amazonians. Likely they are hiding somewhere…but the ancient DNA sampling is getting pretty good. We’re missing something. Third, I am not sure what to think about the very rapid bifurcation of lineages we’re seeing around ~40,000 years ago.
The ANS population, ancestral by and large to ANE, seems to be about ~75% West Eurasian (without much Basal Eurasian) and ~25% East Eurasian. Or at least that’s one model. Did they then absorb other peoples? Or, was there an ancient population structure in the primal ur-human horde pushing out of the Near East? That is, are the “West Eurasians” and “East Eurasians” simply the descendants of original human tribes venturing out of Africa ~50,000 years ago? Also, rather than discrete West Eurasian and East Eurasian components, perhaps there was a genetic cline where the proto-ANS occupied a position closer to the former, as opposed to some later pulse admixture?
Without more ancient DNA we probably won’t be able to resolve the various alternative models.
Ten years ago when I read Peter Heather’s Empires and Barbarians, its thesis that the migrations and conquests of the post-Roman period were at least in part folk wanderings, where men, women, and children swarmed into the collapsing Empire en masse, was somewhat edgy. Today Heather’s model has to a large extent been validated. The recent paper on the Lombard migration, the discovery that the Lombards were indeed by and large genetically coherent as a transplanted German tribe in Pannonia and later northern Italy, confirms the older views which Heather attempted to resurrect. Additionally, the Lombards also seem to have been defined by a dominant group of elite male lineages.
Why is this even surprising? Because to a great extent, the ethnic and tribal character of the post-Roman power transfer between Late Antique elites and the newcomers was diminished and dismissed for decades. I can still remember the moment in 2010 when I was browsing books on Late Antiquity at Foyles in London and opened a page on a monograph devoted to the society of the Vandal kingdom in North Africa. The author explained that though the Vandals were defined by a particular set of cultural codes and mores, they were to a great extent an ad hoc group of mercenaries and refugees, whose ethnic identity emerged de novo on the post-Roman landscape.
In the next few years, we will probably get Vandal DNA from North Africa. I predict that they will be notably German (though with admixture, especially as time progresses). Additionally, I predict most of the males will be haplogroup R1b or I1. But the Vandal kingdom was actually one where there was a secondary group of barbarians: the Alans. It was Regnum Vandalorum et Alanorum. I predict that Alan males will be R1a. In particular, R1a1a-z93.
But this post is not about the post-Roman world. Rather, it’s about the Inner Asian forest steppe. The sea of grass, stretching from the Altai to the Carpathians. A new paper in Science adds more samples to the story of the Srubna, Cimmerians, Scythians, and Sarmatians. Ancient genomes suggest the eastern Pontic-Caspian steppe as the source of western Iron Age nomads. The abstract is weirdly nonspecific, though accurate:
For millennia, the Pontic-Caspian steppe was a connector between the Eurasian steppe and Europe. In this scene, multidirectional and sequential movements of different populations may have occurred, including those of the Eurasian steppe nomads. We sequenced 35 genomes (low to medium coverage) of Bronze Age individuals (Srubnaya-Alakulskaya) and Iron Age nomads (Cimmerians, Scythians, and Sarmatians) that represent four distinct cultural entities corresponding to the chronological sequence of cultural complexes in the region. Our results suggest that, despite genetic links among these peoples, no group can be considered a direct ancestor of the subsequent group. The nomadic populations were heterogeneous and carried genetic affinities with populations from several other regions including the Far East and the southern Urals. We found evidence of a stable shared genetic signature, making the eastern Pontic-Caspian steppe a likely source of western nomadic groups.
The German groups which invaded the Western Roman Empire were agropastoralists. That is, they were slash and burn farmers who raised livestock. Though they were mobile, they were not nomads of the open steppe. Man for man the Germans of Late Antiquity had more skills applicable to the military life than the Roman peasant. This explains in part their representation in the Roman armed forces in large numbers starting in the 3rd century. But the people of the steppe, pure nomads, were even more fearsome. Ask the Goths about the Huns.
Whole German tribes, like the Cimbri, might coordinate for a singular migration for new territory, but for the exclusive pastoralist, their whole existence was migration. Groups such as the Goths and Vandals might settle down, and become primary producers again, but pure pastoralists probably required some natural level of predation and extortion upon settled peoples to obtain a lifestyle beyond marginal subsistence. Which is to say that some of the characterizations of Late Antique barbarians as ad hoc configurations might apply more to steppe hordes.
There has been enough work on these populations over the past few years to admit that various groups have different genetic characteristics, indicative of a somewhat delimited breeding population. But, invariably there are outliers here and there, and indications of periodic reversals of migration and interactions with populations from other parts of Eurasia.
Earlier I noted that Heather seems to have been correct that the barbarian invasions of the Roman Empire were events that involved the migration of women and children, as well as men. The steppe was probably a bit different. Here are the Y and mtDNA results for males from these data that are new to this paper:
There was some question regarding possible Scythian admixture into the early Zhou below. This is possible because of the Zhou dynasty, arguably the foundational one of Chinese imperial culture (the Shang would have been alien to Han dynasty Chinese, but the Zhou far less so), may have had interactions with Indo-European peoples to their north and west. This has historical precedent as the Tang dynasty emerged from the same milieu 1,500 years later, albeit the Tang were descended from a Turkic tribe, not Indo-Europeans.
I looked at some of my samples and divided the Han into a northern and southern cluster based on their position on a cline (removing the majority in between). I also added Lithuanians, Sardinians, Uyghurs, Mongols, and Yakut. As you can see on the PCA the Mongols are two clusters, so I divided them between Mongol and Mongol2.
A comment below suggested another book on Vietnamese history, which I am endeavoring to read in the near future. The comment also brought up issues relating to the ethnogenesis of the Vietnamese people, their relationship to the Yue (or lack thereof) and the Khmer, and also the Han Chinese.
Obviously, I can’t speak to the details of linguistics and area studies history. But I can say a bit about genetics because over the years I’ve assembled a reasonable data set of Asians, both public and private. The 1000 Genomes collected Vietnamese from Ho Chi Minh City in the south. I compared them to a variety of populations using ADMIXTURE with 5 populations.
You can click to enlarge, but I can tell you that the Vietnamese samples vary less than the Cambodian ones, and resemble Dai more than the other populations. The Dai were sampled from southern Yunnan, in China, and historically were much more common in southern China, before their assimilation into the Han (as well as the migration of others to Southeast Asia).
Curiously, I have four non-Chinese samples from Thailand, and they look to be more like the Cambodians. This aligns well with historical and other genetic evidence the Thai identity emerged from the assimilation of Tai migrants into the Austro-Asiatic (Mon and Khmer) substrate.
Aside from a few Vietnamese who seem Chinese, or a few who are likely Khmer or of related peoples, the Vietnamese do seem to have some Khmer ancestry. Or something like that.
That sound you hear is the rumbling of the earth caused by the rippling tsunami that’s coming. The swell of ancient DNA papers focused on historical, rather than prehistorical, time periods. Some historians are cheering. Some are fearful. Others know not what to think. It will be. The illiterate barbarians of yore shall come out of the shadows.
If they had arrived on the edge of Europe two centuries earlier, the Avars would have a reputation as fearsome with the Huns, with whom they are often confused, and rightly so. But the Avars emerged as a force on the European landscape after the end of the West Roman Empire. The post-Roman polities did not have their own Ammianus Marcellinus (sorry Bede, you lived in the middle of nowhere).
And yet for centuries the Avars dominated east-central Europe and held the numerous Slavic tribes in thrall. They smashed past the borders of Byzantium during the reign of the heir of Justinian, and by 600 AD, on the eve of the great battle with Persia Constantinople had lost control of most of its Balkan hinterlands to these barbarians. A Byzantium which still controlled North Africa, much of Italy, southern Spain, Egypt, Anatolia, and the Levant, had been reduced to strongpoints all around the Balkan littoral. During the wars with the Sassanids, the Avars took advantage of the opportunity offered, and even raided the suburbs of Constantinople itself!
So who were these people? The most plausible conjecture is that they were part of the great mass mobilization of Turkic peoples which began in the early centuries of the first millennium after Christ. As Rome and Han China fell, nomadic barbarians rose. A new preprint seems to all but confirms this, Inner Asian maternal genetic origin of the Avar period nomadic elite in the 7th century AD Carpathian Basin:
After 568 AD the nomadic Avars settled in the Carpathian Basin and founded their empire, which was an important force in Central Europe until the beginning of the 9th century AD. The Avar elite was probably of Inner Asian origin; its identification with the Rourans (who ruled the region of today’s Mongolia and North China in the 4th-6th centuries AD) is widely accepted in the historical research. Here, we study the whole mitochondrial genomes of twenty-three 7th century and two 8th century AD individuals from a well-characterised Avar elite group of burials excavated in Hungary. Most of them were buried with high value prestige artefacts and their skulls showed Mongoloid morphological traits. The majority (64%) of the studied samples’ mitochondrial DNA variability belongs to Asian haplogroups (C, D, F, M, R, Y and Z). This Avar elite group shows affinities to several ancient and modern Inner Asian populations. The genetic results verify the historical thesis on the Inner Asian origin of the Avar elite, as not only a military retinue consisting of armed men, but an endogamous group of families migrated. This correlates well with records on historical nomadic societies where maternal lineages were as important as paternal descent.
The samples were from a period about a century after the arrival of the Avars. It is not unreasonable to think that the Avar conquest meant that a continuous stream of Inner Asian pastoralists kept entering into the territory which they occupied for the opportunity, but this sort of genetic distinctiveness indicates that the Avars remained very separate from the people from whom they extracted tribute. Most, though not all, of these people, were or became Slavs.
Around 800 AD the Avars were finally defeated decisively by the Franks, and their elite converted to Christianity. I suspect this was the final step which would result in their assimilation over the next few centuries into the location population until they diminished and disappeared.
The results above support the proposition that the Pannonian Avars of the second half of the 6th century were the descendants of the Rouran Khaganate of the early half 6th century. The kicker is that the Rouran flourished in Mongolia! So like the Mongols six hundred years later, the Avars seem to have swept across the entire length of Eurasia that was accessible to their horses in a generation. To some extent, this is a recapitulation of the pattern we see nearly 3,000 years before the Avar, when the Afanasievo culture established itself in the Altai region, far from its clear point of origin in the forest-steppe of Eastern Europe.
Perhaps the period between 500 BC and 300 AD can be seen as an ephemeral transient between the vast periods before and after when pastoralists had free reign across most of temperate Eurasia?