Comparing genes across
linguistic families
Guido Barbujani
Princeton, Institute of Advanced Study October 2014
“If we possessed a perfect pedigree of mankind, a genealogical arrangement of the races of man would afford the best classification of the various languages now spoken throughout the world...”
-Charles Darwin, The Origin of Species, 1859
In turn, language data are useful to help us understand biological diversity and migration processes
AC
B
History
A common language frequently signifies a common origin and a related language indicates a common origin further back in time. Such commonality of origin should be reflected by genetic relationship, despite several complicating factors.
Robert R. Sokal (1988) Proc. Natl. Acad. Sci. USA
Summary
1.Migrations are population, not molecular, processes
2.Classical comparisons of genes and languages
3.The trouble with the vocabulary and an alternative approach
4.Comparing genes across language families
Fig. 1. The first principal component of gene frequencies from 38 independent alleles at the human loci: ABO, Rh, MNS, Le, Fy, Hp, PGMi, HLA-A, and HLA-B. Shades indicate different intensities of the first principal component, which accounts for 27 percent of the total variation
It all began from this
P. Menozzi, A. Piazza & L.L. Cavalli-Sforza (1978) Science
Continentwide genetic gradients in Europe
L.L. Cavalli-Sforza et al. (1994) Science
Diffusion of Neolithic artifacts in Europe
P. Balaresque et al. (2010) PLoS Biology, interpolated from data by R. Pinhasi et al.
Rationale for the proposal of a Neolithic demic diffusionEuropean genetic diversity distributed in gradients. Only gene flow can generate such patterns on the continental scale
No documented migration in post-Neolithic times spanning the area from the Levant to the Atlantic coasts
Neolithic technologies may have spread by cultural contact or by migration (most likely, by a combination thereof)
Diffusion of Neolithic artifacts cannot produce genetic clines if it is caused only by cultural contacts
Demic diffusion: expanding Neolithic people carried in Europe their know-how, their genes, and perhaps their languages too.
E. Kitchen et al. (2009) Proc. R. Soc. B
Their languages too?
C. Renfrew (1987) Archaeology and language: The puzzle of Indo-European origins
Their languages too?
Conditions for the origin of genetic gradients by demic diffusion
1. Demographic growth of farmers
2. Diffusion, incomplete admixture
3. Farmers continue to grow in numbers, hunter-gatherers don’t
A.J. Ammerman & L.L. Cavalli-Sforza (1984) The NeolithicTransition and the Genetics of Populations in Europe
But…
0. Low population density
In the first DNA studies (mtDNA) very old ages are estimated for the
main European mutations
“Each cluster can be assigned, in its entirety, to one of the proposed migration phases; the age of each cluster approximates very closely the timing of the migratory event”
“The main mitochondrial variants in Europe predate the Neolithic expansion”
(M. Richards et al. (1996, 2000) Am. J. Hum. Genet.
Estimated ages of mitochondrial haplogroups (x 1000)
Richards Sykes Richards et al. 1996 1999 et al. 2000
H 23.5 11.0-14.0 15.0 - 17.2 J 23.5 8.5 6.9 - 10.9 T 35.5 11.0-14.0 9.6 - 17.7 IWX 50.5 11.0-14.0
X: 20.0 I: 19.9 - 32.7 K 17.5 11.0-14.0 10.0 - 15.5 U 36.5 5: 50.0 44.6 - 54.4
Neolithic contribution overestimated in preDNA studies? Hans Bandelt
Haplogroup H, “the signature of the Paleolithic expansion in Europe”
Two basic models
Palaeolithic model Neolithic model (Cultural diffusion of food- (Demic diffusion of food- production technologies production technologies
G. Barbujani (2012) Curr. Biol.
Ok folks, all those with haplogroup H come with me, let’s do the Paleolithic
migration. No way Steve, not you. You’re a J, damn it, a J! Wait until the Neolithic!
“Each cluster can be assigned, in its entirety,to one of the proposed migration phases; the age of each cluster
approximates very closely the timing of the migratory event”
Ancient DNA evidence: Neolithic Europeans did not only carry the J hg, no evidence of the H hg in Paleolithic Europeans
20,00055,00045,0007,70022,70013,60012,000
Haplogroup estimated age
21 pre-neolithic hunter-gatherers 105 Nolithic farmers
Post Pr (Model B): 1,655 to 2,691 folds as high as Post Pr (Model A)
Genetic continuity since Paleolithic times very unlikely in ABC analyses of mtDNA
2 individuals from the Upper Paleolithic, 43 from the Mesolithic (including the two La Braña specimens) and 121 from the Neolithic
It is people who migrate, not haplogroupsHaplogroup ages are not estimates of migration times
Summary
1.Migrations are population, not molecular, processes
2.Classical comparisons of genes and languages
3.The trouble with the vocabulary and an alternative approach
4.Comparing genes across language families
Often, genetic isolates are also linguistic isolates
F. Calafell & J. Bertranpetit (1993) Am. J. Phys. Anthropol.
In Europe, linguistically-related populations are genetically closer than unrelated populations separated by the same geographic distance
Correlations Positive, significant • GEO,LANG 26 / 26• GEO,GEN 22 / 26• GEN,LANG 16 / 26• GEN,LANG.GEO 11 / 26
R.R. Sokal (1988) Proc. Natl. Acad. Sci USA
In agreement with Renfrew’s predictions, four African-Eurasian gradients corresponding to four language families
G. Barbujani & A. Pilastro (1993) Proc. Natl. Acad. Sci .USA
R.D. Gray & Q.D. Atkinson (2003) Nature
In agreement with Renfrew’s predictions, estimated
divergence between Indo-European languages
between 7,800 and 9,500 years BP
R. Bouckaert et al. (2012) Science
In agreement with Renfrew’s predictions, geographic origin of the Indo-European family inferred in Anatolia
But no gene-language correlation in the Americas
A simple, global correspondence between genetic and linguistic
diversity?
1. Do we speak different languages because our genes influence language learning?
2. Do we carry different alleles because we speak different languages?
L.L. Cavalli-Sforza et al. (1988) Proc. Natl. Acad. Sci. USA
Summary
1.Migrations are population, not molecular, processes
2.Classical comparisons of genes and languages
3.The trouble with the vocabulary and an alternative approach
4.Comparing genes across language families
Many linguists disagree
Controversial linguistic classifications
Random similarities due to the limited number of sounds humans can produce
Impossibility to tell random from significant correspondences if etimologies cannot be traced
Overlapping cultural boundaries
The trouble with vocabulary comparisons
An alternative to vocabulary comparisons: Structural features of languages in grammar and syntax
Word order Englishequivalent
Proportionof languages
Examplelanguages
SOV "She him loves." 45% Pashtoon, Japanese, Afrikaans
SVO "She loves him." 42% English, Hausa, Mandarin
VSO "Loves she him." 9% Hebrew, Tuareg, Zapotec
VOS "Loves him she." 3% Malgasy, Baure
OVS "Him loves she." 1% Hixkaryana
OSV "Him she loves." <1% Warao
The Parametric Comparison MethodG. Longobardi & C. Guardiano (2009) Lingua
Summary
1.Migrations are population, not molecular, processes
2.Classical comparisons of genes and languages
3.The trouble with the vocabulary and an alternative approach
4.Comparing genes across language families
5,886 subjects genotyped at 500,568 loci using the Affymetrix 500K single nucleotide polymorphism (SNP) chip.
POPRES populations that match our linguistic database in Europe
Genetic data
Populations: England, France, Germany, Greece, Hungary, Ireland, Italy, Poland, Portugal, Romania, Russia, Serbia, Croatia, Spain
20 Spanish Basques
+ Basque
+ Finnish93 Finns
Final sample size:805 individuals for ~ 220,000 SNPs (MAF > 0.01 and genotyping rate > 98%)
Principal Component Analysis (PCA) of individual genotypes
A matrix summarizing structural variation in 15 European languages
PCAnalysis of languages
Language diversity
Genomic diversity
Common elements and differences between PCA plots of genomic and linguistic diversity
Main inconsistencies:1.Hungarians genomes close to those of Indo-European speakers2.Romanian genomes close to those of their geographical, non-Romance speaking, neighbours
Among Indo-European languages, distances inferred from vocabulary and syntax suggest similar clusterings
Vocabulary Syntax
In Europe, distances inferred from syntax and DNA suggest similar clusterings
Syntax Genetic distances
Path difference distance between linguistic and genetic UPGMA
Comparison with those obtained in 100,000 pairs of random topologies drawn, with replacement, from the total set of the possible topologies for 15 taxa
Probability to obtain smaller distance values than observed, P<0.004
The close relationship between trees inferred from linguistic and genetic distances is very unlikely to have arisen just by chance
Mantel correlations between distance matrices
Bonferroni P=0.0006
Mantel and partial Mantel correlations between distance matrices
Bonferroni P=0.006
Main inconsistencies:1.Hungarians genomes close to those of Indo-European speakers2.Romanian genomes close to those of their geographical, non-Romance speaking, neighbours
Recent admixture accounts for some PCA inconsistencies
To summarize:
1.Within the Indo-European family, similar trees inferred from vocabulary and
syntactic comparisons
2.European populations speaking similar languages also tend to resemble each
other at the genomic level
3.Syntax appears to offer a better prediction of genomic distances than geography
4.Contacts between populations after their separation from a common ancestor
can be recognized, and better accounted for, by comparing genomic and linguistic
patterns of variation
When did the main human populations
separate?
Henn et al. (2012) Proc Natl Acad Sci USA
Scally and Durbin (2012) Nature Rev Genet
Fossil, archaeological and genomic evidence place divergence among continental populations in the interval. 120-60 k years ago. When did the main language families diverge?
Correlation suggests, but does not prove, common causation. Would it be possible that the same geographic constraints led to parallel genetic and linguistic change, in different time moments?
Darwin had in mind population trees; but how sure are we that genetic evolution and linguistic change really occurred in a tree-like fashion?
Indoeuropean Documentation Center, Utexas at Austin
Several open questions
Silvietta Ghirotto
Francesca Tassi
Pino LongobardiYork University
Davide PettenerUniversity of Bologna
http://www.langelin.org/
Cristina GuardianoUniversity of Modena