Nuragic Sardinians are still among us, the Etruscans aren’t. Two genealogical studies

Guido Barbujani

Dip. Biologia ed Evoluzione Università di Ferrarag.barbujani@unife.it

Nuragic Sardinians resemble some modern Sardinians

Genetic map of Europe (Menozzi, Piazza, Cavalli-Sforza 1978)

53 tooth samples from 6 nuragic sites

Elimination of samples that do not comply with the strictest quality standards

10 different sequences in 23 nuragic individuals

h, haplotype diversity=0.83

Etruscans: 0.95Tuscans: 0.96Basques: 0.96Greeks: 0.98Sicilians: 0.96

Ogliastra 0.78Gallura 0.93

North Africa: 13.9 4

Near East: 10.7 6

Europe: 18.3 8

Iberians: 29.4 2Etruscans: 22.2 4

Shared sequences among Nuragic people and other modern and ancient populations

Gallura: 18.5 1Ogliastra: 54.6 4

The Etruscans do not resemble modern Tuscans

A bit of history

Etruscan a non-Indo-European languageDocumented from the end of VIII century BCEtruscan cities independent statesCommon culture and language, but never a political unitMaximum territory expansion: VI century BCMilitary defeats, Roman assimilation in the II century BC

Dionysius of Halicarnassus: the Etruscans an Italic populationHerodotus: the Etruscans seamen from Lydia, escaping famine

V

A

S

PM

T

C

R o m e

Adria (17, 5), Volterra (6, 3),Castelfranco di Sotto (2, 1),Castelluccio di Pienza (1, 1),Magliano and Marsiliana (25, 6)Tarquinia (18, 5), Capua (8, 6)

80 bone samples from 8 Etruscan necropoleis

27 individuals, 22 different haplotypes, h=0.946

Shared sequences between the Etruscans and modern populations

23 3

35

2

1

31

52

22

33

1

3

7

4

2

2

2

4

Genetic distances (Fst x 1000) between the Etruscans and

modern populations

3680 90

7048

74

118

5550

37

47

4176

6051

57

261

69

65

41

62

73

71

Testing hypotheses by serial coalescent simulation

Reconstructing (proceeding backwards in time) the maternal genealogy of a sample

Two possibilities: either each individual has a different mum

Or two individuals have the same mum (coalesence)

Coalescence probability a function of population size N and sample size n

Past

Present

GenealogiesMRCA

N = 10N constantn = 69 generations

Mutation

Mutation

1

CAATG

CAATA

CAGTG

TAATA

CAATG CAGTG CAGTGCGGTG TAACA TAATA

TAACA1 2 3 3 4 5

Il Modello: Serial Simcoal

Serial coalescence

N=20Modern sample (n=5)0

100

Time(generations)

Ancient sample (n=2)

Anderson C.N.K., Ramakrishnan U., Chan Y.L. e Hadly E.A. (2005) Bioinformatics

INPUT Population size Population growth rate Migration matrix Mutation model and rate Sample sizes and ages

OUTPUT N haplotypes Haplotype diversity Nucleotide diversity Mismatch distribution Haplotype sharing

Etruscans Tuscans Murlo

Sample size 27 49 86

Haplotype n 22 40 60

Haplotype diversity 0.946 0.949 0.960

Nucleotide diversity 0.011 0.014 0.012

Avg. mismatch 3.91 5.03 4.50

Haplotype sharing 0.09 0.14

Fst 0.024 0.028

Observed population statistics

Consistency criterion: overlap between the 95% confidence intervals of observed and simulated statistics

Etruscans and Tuscans a single population?

Nf=25,000

Nf=25,000

r = 0

Model 1: Small population, constant size

• Allele sharing: 4.2% (1.4-8.1) OK

• Hapl. diversity:

- Etruscans: > Obs.

- Tuscans: > Obs.

0

100

Generations

Tuscans

Etruscans

Mutation rate: 1 per million years per nucleotide × 360 nucleotides, × 25 years per generation, ÷2 → 0.0045

Etruscans and Tuscans a single population?

Nf=300,000

Nf=25,000

r = -0.025

Model 3: Expanding population

• Allele sharing: 5.0% (1.3-9.1) OK• Hapl. diversity:

- Etruscans: > Obs.

- Tuscans: > Obs

0

100

Generations

Tuscans

Etruscans

Only models in which modern Tuscans and Etruscans belong to distinct genealogies are consistent with the data (χ2<31)

Interpretations, doubts

• Unless mutation rate is much higher than currently believed, the Etruscans left very few modern mitochondrial descendants in Tuscany (Belle et al. 2006)

• Did they all go extinct?• Did massive immigration dilute a component of Etruscan origin

in the Tuscans’ mtDNA gene pool?

• Postmortem DNA modifications and/or technical problems affected the Etruscan mtDNA sequences (Achilli et al. 2007)

No evidence of sequence errors in the Etruscan dataset

61 tooth samples from Middle-Age Tuscany Guimaraes et al., in preparation

Joint analysis of11 Etruscan sequences27 Medieval sequences (900-1300 A.D.), from 6 cemeteries

322 (Achilli et al.) and 49 (Francalacci et al.) modern Tuscan sequences

Model 1χ2=110

0 C

E

M

Model 4χ2=142

C

E

M

Only the model in which medieval Tuscans and Etruscans belong to the same genealogy and modern Tuscans don’t is consistent

with the data (χ2<49)

Model 2χ2=122

C

E

M

Model 3χ2=145

C

E

M

Model 5χ2=66

C

E

M

Model 6 χ2=40

E

M

C

Model 7χ2=63

E

M

C

What happened to the Etruscans but not to Nuragic Sardinians?

1. Perhaps the Etruscan we studied represent more a social elite than the entire population

2. Major demographic changes in the last few centuries in the Netherlands (Manni et al. 2002) and in the British Isles Töpf et al. (2007)

Relatively recent immigration has deeply changed the genetic structure of the population in Tuscany and in Gallura, but not in the Iberian peninsula and in Ogliastra

David Caramelli

Giorgio Bertorelle

Andrea Benazzo, Silvia Ghirotto Loredana Castrì

Elise Belle

Many thanks to

Enza Colonna

Simulation parameters

• Population sizes: Etruscans: 292,000÷12 = 25,000 Tuscans: 3,500,000÷12 = 300,000

• Growth rate: Nt=N0ert → r=1/100 ln 300,000/25,000 = 0.025

• Mutation rate: 1 mutation per million years per nucleotide × 360 nucleotides, × 25 years per generation, ÷2 → 0.0045

• 360 nucleotides

• Transition bias: 0.94

Only the model in which medieval Tuscans and Etruscans belong to the same genealogy and modern Tuscans don’t is consistent

with the data (χ2<49)