[This is a critique I wrote to form my part of an article I co-wrote with Prof Martial Staub (Sheffield) about genetics and archaeology. Later I cut it down, with the idea of publishing the more detailed elements as 'online supplementary materials'. It didn't get published, sadly. I think that there were two main problems: one was a significant jump in the scale and breadth of Martial's part and mine; the other was that detailed critique like this is maybe what needs to happen before an article like that under discussion comes out, rather than afterwards. Nonetheless, I think this detailed critique is worth making, and if anyone does know of a journal or other publication that might be interested in considering this (or a shorter version of it), do please let me know.
I have split the piece into three shorter blogs for ease of reading. This part contains the introduction and discussion of the problems involved in the setting up of the 'experiment'; part 2 discusses methods and results; and Part 3 contains the overall conclusions, and an afterword.]
Introduction
As a more specific focus for our critique, we consider one
particular study which made something of a media splash in 2018.[1]
This thought-provoking piece compares evidence from a cemetery at Szólád near
Lake Balaton in modern Hungary (Late Antique Pannonia) and another at Collegno in
Piemonte, Italy, two areas linked historically by the sixth-century Longobard
(or Lombard) Migration to Italy. The analyses revealed discrete groups within
both cemeteries, showing different genetic traits, which were related to
northern and southern Europe. These groups correlated with different methods of
burial and (to a lesser degree) in terms of their diet.
When it appeared, the link to the online publication was retweeted by
one Twitter account with the claim that ‘Peter Heather was right. The
Völkerwanderung was a thing!’[2]
We can leave aside for now the point that Heather certainly was right, for the very
good reason that no serious scholar has ever denied that the ‘Great Migrations’
happened.[3]
What requires more rigorous examination is whether this article supports the
interpretation of the Barbarian Migrations that lies behind the term ‘Völkerwanderung’:
not simply a large-scale, short-term population movement, but one that
introduced novel cultural practices into the regions where the migrants
eventually settled. More specifically, we can ask whether it does anything to
help us ‘understand’ ‘6th-century barbarian social organization and migration’,
as its title proclaims. Here the problem might be a disciplinary divergence in the
meaning of the phrase ‘understanding society’ but, if viewed in a purely
historical or archaeological sense, my answer will be definitive: no, it
doesn’t. It describes two situations where people had (in some way) moved into a
specific locality from elsewhere and had (possibly) used different burial
practices. That is valuable. If, however, we want to understand those specific local phenomena and, a fortiori,
if we wish to draw conclusions from them about the wider events of the
‘Barbarian Migrations’, I will demonstrate that we are no further on than when
we were at the start. The only way in which the micro (local) and macro
(pan-European) phenomena can be linked is via a number of uncritical
assumptions, which the publication in question does nothing to interrogate.
Those assumptions are, first, that if migration occurred then that must have been ‘barbarian’ and,
second, that social organisation and variation in material culture must be explained by migration.
In other words, the fact of ‘barbarian migration’ (which no one is denying) is
the necessary and sufficient cause for late antique population and cultural
change. It is in the current climate of ‘push-back’ against, and indeed flagrant
misrepresentation of the views of,[4]
those who deny a unique causal primacy to the Völkerwanderung, the enthusiastic
expostulation about how science had proven that the Great Migrations were ‘a
thing’ finds its context.
A more critical look at the analysis and its approaches is, however,
necessary.[5]
The popular reception of such studies and the nature of their media coverage
are heavily grounded in suppositions that the methods of laboratory science are
superior to the inevitably subjective assumptions and opinions of the historical
disciplines and the partial – in both senses of the word – nature of their
evidence.[6]
Popularly, the epistemological claims of ‘hard science’ trump those of the arts
and humanities. The Online Supplementary Materials (hereafter OSM) of the
article under discussion set out the procedures employed in the laboratory analyses
and mathematical modelling. I can see no reason to comment critically on these.
It is no part of this discussion to cast – or even to imply – any doubts upon
their quality and rigour. Whatever else one might say, it is an impressive
piece of mathematical modelling and complex data analysis. My critique departs
instead from consideration of the study’s rigour as a scientific experiment and
thus confronts the broader epistemological claims. To anticipate my
conclusions, my argument will be that – in
that more general sense – the experiment represents bad science.
Setting up the experiment
The authors describe the experiment and its
results thus:
[W]e obtained ancient genomic DNA from 63 samples from two cemeteries (from Hungary and Northern Italy) that have been previously associated with the Longobards, a barbarian people that ruled large parts of Italy for over 200 years after invading from Pannonia in 568 CE. Our dense cemetery-based sampling revealed that each cemetery was primarily organized around one large pedigree, suggesting that biological relationships played an important role in these early medieval societies. Moreover, we identified genetic structure in each cemetery involving at least two groups with different ancestry that were very distinct in terms of their funerary customs. Finally, our data are consistent with the proposed long-distance migration from Pannonia to Northern Italy. [Emphasis added]
The experiment was designed to confront the following questions:
Were specific barbarian peoples described in texts culturally and ethnically homogeneous populations, or were they ad-hoc and opportunistic confederations of diverse, loosely connected groups? What role did biological relatedness, being that of close kinship relations or long-term shared ancestry, play in the organization of these barbarian communities and how are such relationships related to patterns of material culture? Did this period involve long-distance migrations as described by late antique authors?
The most troubling aspect of the experiment concerns the way it was
shaped by assumptions about its likely results. The OSM include a brief history
of the Longobards but not one of late antique northern Italy and its long
history of social, cultural, economic, and political relationships with
transalpine areas. A reader of the article and its supplementary materials can
be forgiven for believing – entirely incorrectly – that the Longobard movement
was the only significant migration into Italy to occur in the period.
Furthermore, the cemetery-sites investigated are located in the regions linked
by historical accounts of the Longobard migration. In other words, the
selection of data was made on a priori grounds. Now, genetic scientists
might be led to believe that the epistemological status of the ‘Longobard’
label or identifier attached to the sites from which their samples were drawn
was much more secure than it is in actuality, or that such a label might imply
a genetically discrete population. They can understandably not be familiar with
the broader historical and archaeological issues to which we shall return. One
may therefore assume a ‘good faith’ procedure on their part in accepting
certain parameters in the setting up of the experiment.
Fundamentally, though, one must ask where
the control sample is. Assessment of the results’ significance requires
comparable analysis of other sites either from the same period but not
connected by the Longobard migration, or in the same regions but from a
slightly earlier period. The main comparative aDNA evidence used was a pan-European
range of samples from the Bronze Age, 1500 years or more before the Longobards’
migration.[7]
This is insufficient. One needs comparanda from, say, the middle Roman period. A
few early medieval samples were considered but their selection was problematic.
A cluster taken from a 4th-7th-century English context was
listed as ‘Anglo-Saxon’. Others, from the Caucasus, were labelled as being
‘Alans’. This raises questions in the context of a study of Barbarian Migrations
as these names are late antique or early medieval ethnonyms not necessarily
linked to genetics or to material culture in any straightforward way. In
particular, the term ‘Anglo-Saxon’ implies that these subjects had migrated
into the Empire, in this case into the diocese of Britanniae. When
linked to the burials of supposed migrants in Hungary and Italy it risks giving
the impression of a shared ‘barbarian’ origin.
Only six Italian aDNA samples were consulted
in the whole analysis, all from prehistory, and three from the same site. On
the basis of this lacuna alone, one is entitled to doubt the results’ validity.
The authors state that what they consider to be ‘northern’ DNA is otherwise
unknown in Italian samples.[8]
This is illogical unless one assumes, a priori, that those graves with
such DNA at Collegno were not of Italians. The only Italian aDNA from the relevant period to be considered was
that at Collegno, so it is equally true to say that ‘northern’ DNA was found in
every early medieval Italian population examined in the study. Without
appropriate comparanda it is not possible to know how atypical this profile
would be for a late antique cemetery in the Po valley. The only mitigation
again concerns the information passed to the genetic scientists. If the assumption,
made in good faith, was that Szólád and Collegno were both sites that could
reasonably be accepted as having had Longobard populations, then the issue of a
control might possibly have been seen as moot. If the Longobard nature of these
cemeteries, their populations, and some of their material culture is taken as a
given, its correlation with other variables being the subject of analysis, it
does not need testing.
But therein lies the problem. On what basis
is either Szólád or Collegno ‘Longobard’? The assignment of ethnic identities
to forms of archaeological evidence has been hotly debated for over thirty
years.[9]
The Szólád/Collegno analyses were initially intended to contribute critically
to this debate. While many archaeologists now accept that giving ethnic labels
to forms of material culture is dubious, these reservations and the newer
interpretations which they have engendered have been bitterly resisted;
Longobard archaeology is one of the more conservative areas in this respect.[10]
This problem even affects the sites’ dating. The earliest period of ‘Longobard’
archaeology begins in 568 precisely, because (so runs the argument) there were
no Longobards in Italy before 568 and the material is Longobard. The ethnicity
of the associated people is thus entirely prejudged. The same is true in
Hungarian archaeology where, conversely, Longobard material cannot be later
than 568. There is no archaeological reason to suppose that the first phase of
‘Longobard’ burials at Collegno could not belong to a period perhaps ten (or
more) years before 568. Archaeological periodisation cannot be fine-tuned to
that level of accuracy and the development of its techniques over the past forty
years has shown that phases of change can drift back or forward by decades. For example, a key archaeological transition in artefact-forms
which, in the 1980s, was dated to ‘c.600’ is now placed closer to 575/80.[11] The extent to which early Italian
‘Longobard’ material is still generally congruent with comparative material
from the period after 568 is unclear. Without the influence of the historical
record, some of it could unproblematically be placed earlier. Equally, there is
no archaeological reason why Szólád could not have been used for a decade or more
after 568. Overall, there are no prima facie archaeological grounds for supposing
that the earliest phase at Collegno is not contemporary with the last period at
Szólád, whether before, after, or straddling 568. This must
influence how we employ cemetery evidence to think about trans-Alpine
connections and the Longobard migration.
The link between this material and the
Longobards’ arrival is, however, too well entrenched in most Italian
archaeology to permit detailed or rigorous scrutiny of the idea. Indeed, the
archaeology of this period is currently experiencing a backlash against
attempts to reassess the role of Barbarian migration in material cultural
change, further making critical revaluation unlikely. The lead-author of the OSM
Collegno discussion has written a forceful – if unconvincing – defence of the traditional
idea that ethnicity is manifest in late antique burial customs[12]
and the lead-author of the Szólád discussion subscribes to a similar viewpoint.[13]
The team involved in the Szólád-Collegno analyses included only archaeologists
who subscribe to traditional ‘ethnic’ readings of material culture so no
serious consideration was given to alternative interpretations.[14]
Against that background it is extremely difficult to avoid the implication that
incomers distinguished from locals are to be identified as Longobards.
We must also scrutinise the assumptions
about the nature of population movement, which can be illustrated with three
quotations:
While previous sampling from the era has
been limited, we note that published fourth- to seventh-century genomes from
Britain, Bavaria, Lithuania, and the Caucasus, analysed alongside our own
ancient samples, cluster close to their modern counterparts.
We found no evidence that such ancestry was
present in northern Italy during this time (who instead resemble modern
southern and Iberian Europeans), which would be consistent with inferred long
term barriers to gene flow in Europe across the Alps.
Modern European genetic variation is
generally highly structured by geography.[15]
The fundamental assumption is of long-term population immobility,
against which seemingly rare migration can be set and, one assumes, be clearly
identifiable. Whatever the scientific grounds, historically it is a counterfactual.
As will be discussed later, movement of individuals or large groups across the
Alps, in both directions, has been constant since prehistory. Instead, support was
drawn from an article claiming that the study of a person’s DNA allowed their
geographical origins to be reliably estimated even to village level.[16]
This conclusion was reached from analysis of populations from three islands off
Scotland, three villages in the Alps, and three villages in Croatia. When separated
by up to thirty miles of sea or several thousand metres of mountain, it is
scarcely surprising that marriage tended to take place within each individual
locality. The Croatian case study, where such natural barriers were absent, was
far less conclusive. Another support was a study of the British Isles which
claimed that modern British DNA showed the persistence of the political units
of the ‘Dark Ages’[17]
but actually came, very clearly, to the hardly staggering conclusion that
people in low-lying arable areas find it easier to move around to find sexual
partners than those living in the middle of mountain ranges.[18]
Some of these issues resurface when considering the experiment’s methods. The
logical accompaniment to the idea that difficult physical geography creates
barriers to gene-flow – that areas of easier communication might accelerate it
– seems not to feature anywhere in the cited literature. The methods of
plotting the spatial distribution of particular genetic components[19]
assumed a ‘flat earth model’ – in other words, a genetic feature would normally
diminish across space in an even fashion. This contradicts the assumption that
physical geography presents long term barriers to gene-flow, as indeed does the
very wide geographical spread of modern subjects listed as Swiss.
Notes
[1] ‘Understanding 6th-century barbarian social organization and
migration through paleogenomics’, in Nature
Communications (2018) 9:3547 (DOI: 10.1038/s41467-018-06024-4). For
interesting discussion of the media and aDNA studies, see, Källén, Anna &
Mulcare, Charlotte & Nyblom, Andreas & Strand, Daniel. (2019). ‘Archaeogenetics
in Popular Media: Contemporary Implications of Ancient DNA.’ Current Swedish
Archaeology. 27. 69-91. 10.37718/CSA.2019.04. I am grateful to Oren Falk
for this reference.
[2] This tweet or the account seems subsequently to have been deleted or has 'blocked' me.
[3] Susan Oosthuizen, The Emergence of the English, is the latest attempt to deny that there was an Anglo-Saxon migration but her argument is extremely problematic.
[4] G.P. Brogiolo, ‘Dati archeologici e beni fiscali nell’Italia
Goto-Longobarda’ in Between Taxation and Rent: Fiscal Problems from Late
Antiquity to the Early Middle Ages/Entre el Impuesto y la Renta. Problemas de
la fiscalidad tardoantigua y altomedieval, ed. P.C. Díaz & I. Martín
Viso (Bari, 2011), pp.87-105, at p.100; G.P. Brogiolo & A. Chavarría Arnau,
‘Chiese e insediamenti rurali tra V e VIII secolo prospettive della ricerca
archeologica’ in ‘Ipsam Nolam barbari vastaverunt’: L’Italia e il
Mediterraneo occidentale tra il V secolo e la metà del VI. Atti del Convegno
internazionale di studi (Cimitile-Nola-Santa Maria Capua Vetere, 18-19 giugno
2009), ed. C. Ebanista & M. Rotili (Cimitile, Tavolario edizioni,
2010), pp.45-62, at 46-47.
[5] In 2019 I presented a preliminary critique of this piece at the
University of Sheffield. The authors’ response, made before the lecture’s text
was publicly available (at https://600transformer.blogspot.com/2019/03/the-barbarian-migrations-in-21st-century.html), was dismissive at best. Cp. the similarly
aggressive response by the authors of Charlotte Hedenstierna-Jonson et al., “A Female Viking Warrior Confirmed
by Genomics,” American Journal of
Physical Anthropology 164.4 (2017): 853-60, to Judith Jesch’s similarly
blogged response: “Let’s Debate Female Viking Warriors Yet Again,” Norse and
Viking Ramblings (9 September 2017) http://norseandviking.blogspot.com/2017/09/lets-debate-female-viking-warriors-yet.html.
Källén et al., ‘Archaeogenetics in Popular Media’, p.85. I am grateful
to Oren Falk for letting me read his unpublished paper ‘Death and the
Shield-Maiden: Viqueering Vikings and Viquens’, a detailed critical discussion
of the supposed woman-warrior found at Bjirka and the ensuing debate.
[6] Källén et al., ‘Archaeogenetics in Popular Media’.
[7] Below, n.28.
[8] Amorim et al. ‘Understanding’, p.5.
[9] This debate was reignited by G. Halsall, ‘The origins of the Reihengräberzivilisation:
Forty Years on.’, in Fifth-Century Gaul: A Crisis of Identity? Ed. J.F.
Drinkwater and H. Elton (Cambridge, 1992), pp.196-207; G. Halsall, ‘Archaeology
and the late Roman frontier in northern Gaul: the so-called Föderatengräber
reconsidered’, in Grenze und Differenz im früheren Mittelalter, ed. W.
Pohl & H. Reimitz (Vienna, 2000), pp.167-80. These studies are reprinted in
G. Halsall, Cemeteries and Society in Merovingian Gaul. Selected Studies on
History and Archaeology, 1992-2009 (Leiden, 2010), pp.93-130, alongside
‘Commentary 2: Careful with that axe, Eugenius’ (pp.131-67), which responds to
critiques made up until about 2010. For similar criticisms of the traditional
ethnic reading, see above all, S. Brather, Ethnische Interpretationen in der
frühgeschichtliche Archäologie (Ergänzungsbande zum Reallexikon der
germanischen Ältertumskunde 42: Berlin, 2004); P. von Rummel, Habitus
Barbarus: Kleidung und Repräsentation spätantiker Eliten im 4. und 5.
Jahrhundert Ergänzungsbande zum Reallexikon der germanischen Ältertumskunde
55: Berlin, 2007); F.J. Theuws & M. Alkemade, ‘A kind of mirror for
men: sword depositions in late antique northern Gaul’, in Rituals of Power.
From Late Antiquity to the Early Middle Ages, ed. F.J. Theuws & J.L.
Nelson (Leiden, 2000), pp.401-76; F. Theuws, ‘Grave-goods, ethnicity and the
rhetoric of burial sites in late antique northern Gaul’, in Ethnic
Constructs in Antiquity. The Role of Power and Tradition, ed. T.
Derks & N. Roymans (Amsterdam, 2009), pp.283-319.
[10] See the works by Brogiolo, above n.4; V. Bierbrauer, ‘’Zur ethnischen Interpretation in der frühgeschichtlichen Archäologie’, in Die Suche nach den Ursprüngen von der Bedeutung des frühen Mittelalters (Vienna, 2004); Kazanski, M., & P. Périn, 2008. ‘Identité ethnique en Gaule à l’époque des Grandes Migrations et des Royaumes barbares: étude de cas archéologiques’. Antiquités Nationales 39, pp.181-216. the articles by Giostra and Vida cited below, n.12
[11] R. Legoux, P. Périn & F. Vallet, Chronologie Normalisée du
Mobilier Funéraire Mérovingien entre Manche et Lorraine (3rd revised
edition; Condé-sur-Noireau, 2009).
[12] C. Giostra ‘Goths and Lombards in Italy: the potential of
archaeology with respect to ethnocultural identification’, Post-Classical
Archaeologies 2011, pp.7-36. There is no space for detailed refutation of
the argument here.
[13] T. Vida, ‘Conflict And Coexistence: The Local Population Of The
Carpathian Basin Under Avar Rule (Sixth To Seventh Century)’, in The Other
Europe in the Middle Ages. Avars, Bulgars, Khazars and Cumans, edited by F.
Curta, Brill, Leiden, 2008, pp. 13–46. Vida dismisses Brather’s work:
‘Brather’s position may be popular with advocates of a post-processualist
critique of both archaeological sources and the methods of the archaeological
inquiry, but it rests on wrong assumptions’ (p.15). He presents no substantive
reasons why this might be the case. He and Giostra both deploy
‘post-processualism’ – a very loose archaeological school of thought of which
neither seems to have a clear understanding – as a sort of bogeyman, and both
rely on the heavily criticised notion of a pan-Germanic culture. For recent
discussion of the latter, see M. Friedrich & J. Harland (ed.) Interrogating
the “Germanic”: A Category and its Use in Late Antiquity and the Early Middle
Ages.
[14] The acknowledgements of Amorim et al., ‘Understanding’,
include thanks, for ‘helpful’ conversations, to Dr Philipp von Rummel and
Professor Frans Theuws, both of whom have published rigorous critiques of the
traditionalist ‘ethnic’ reading of grave-goods (above, n.9). These
conversations have clearly been ignored.
[15] Amorim et al. ‘Understanding’, p.5, p.5, p.9, respectively.
[16] O’Dushlaine, C., et al. ‘Genes predict village of origin in rural
Europe.’ Eur. J. Hum. Genet. 18, 1269–1270 (2010).
[17] Leslie, S., et al. ‘The fine-scale genetic structure of the British
population.’ Nature 519, 309–314 (2015).
[18] Readers should note here the significant difference between the
proposition that mountain ranges act as barriers to gene-flow across
them and the claim that mountains constrain gene-flow among the population
living within the range.
[19] Yang, WY., Novembre, J., Eskin, E., & Halperin, E., A
model-based approach for analysis of spatial structure in genetic data. Nat
Genet 44, 725–731 (2012). https://doi.org/10.1038/ng.2285