Claire Bowern with Keith Hunley and Meghan Healy Yale and University of New Mexico Feb 9 2012 Based on Hunley et al 2012 Rejection of a Serial Founder Effects model Roy Soc Proc B ID: 1046845
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1. Serial Founder Effects in Linguistics and GeneticsClaire Bowern (with Keith Hunley and Meghan Healy)Yale and University of New MexicoFeb 9, 2012Based on Hunley et al: (2012) Rejection of a Serial Founder Effects model… Roy Soc. Proc. B. 2/01
2. Genes and LanguagesConsensus about broad-scale similarities in evolutionary processes in linguistics and geneticsDiscrete heritable units (DNA sequences :: words, phonemes (= distinctive sounds in a language), grammar, etc)… which undergo mutation… at different rates.Can identify homologous features which descend from common ancestors (with understanding of the processes of change, we can reconstruct features of those ancestors)Transmission is both vertical and lateral, with the former (usually) predominatingCan be modeled by trees and networks
3. Genes and LanguagesChange thought to operate at very different time scales:>6000 distinct languages currently spoken, in about 150 families.Much current attested diversity dates to within the last 10,000 years:Indo-European, Uralic, Afro-Asiatic [inc Semitic], Sino-TibetanAustronesian, Pama-Nyungan, Algonquianetc.(Although language has been around for at least 100,000 years.)
4. Atkinson (2011)Claim:Language Shows Serial Founder Effects: “Human genetic and phenotypic diversity declines with distance from Africa, as predicted by a serial founder effect in which successive population bottlenecks during range expansion progressively reduce diversity, … Recent work suggests that a founder effect may operate on human culture and language. Here I show that the number of phonemes used in a global sample of 504 languages is also clinal and fits a serial founder–effect model of expansion from an inferred origin in Africa. This result … points to parallel mechanisms shaping genetic and linguistic diversity and supports an African origin of modern human languages.”
5. Background:Hay and Bauer (2007) showed that there was a weak but significant correlation between number of speakers of a language and the number of distinctive sounds in a language, but could provide no reason for the correlation.Atkinson uses the correlation to hypothesize a SFE process:Correlation points to Founder EffectMigrant populations exhibit a reduced amount of allele/phoneme diversity, which gradually recovers over time. Greatest genetic/phonemic diversity found in AfricaClinal decrease in genetic/phonemic diversity as distance from Africa increases.
6. Atkinson (2011):If true:Language retains information about prehistory for much longer than previously claimed.Therefore important new source of information about global prehistory.However:Atkinson only tested one prediction of a SFE model.
7. Today:Testing further empirical predictions of SFE models in genetic and linguistic samples.Genetics:614 unlinked, autosomal microsatellite loci 2,251 individuals in 100 populations. Linguistics:908 phonemes scored as ‘present/absent’725 languages
8. Languages in Sample
9. Phonemes“distinctive sounds” (sounds which combine to form words and whose substitution causes a change in meaning):English: pat ≠ bat (p and b are distinct phonemes)pʰit ~ spit (p and pʰ are not distinct phonemes; vary by position in word)Bardi:kʰaːra ~ kaːra ~ gaːra ‘uncle’ (kʰ, k, and g are not distinct phonemes)aɹa ‘other’ ≠ ara ‘no’ (ɹ and r are distinct)
10. Four Predictions:Africans will possess more unique alleles/phonemes than people from other regions (number of ‘private’ alleles/phonemes)There will be a negative correlation between within-group variation and geographic distance from the African origin. The pattern of among-group variation will be tree-like, and the trees will be rooted in Africa. The degree of difference among groups will reflect the pattern of branching in the tree. Correlations between patterns of among-group variation and geographic distance will be purely a byproduct of the splitting and movement process, not exchange between neighboring groups.
11. 1: ‘Private’ Alleles/PhonemesMore unique alleles/phonemes in Africa
12. Shared vs Unique Alleles/PhonemesMany fewer phonemes than alleles shared across populations (implies greater rates of change in language)More unique alleles/phonemes in Africa than non-Africa
13. Total vs Private Alleles/Phonemes (by region)
14. 2: Within group variation and geographic distance from AfricaReduced heterozygosity as distance from Africa increases
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16. 3: Tree-like patterns, with tree rooted in Africa
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20. 4: Degrees of difference between groups will reflect branching patterns in tree.[geography will play a role only as a by-product of splitting processes]
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22. Afroasiatic and Africa: Phoneme distance vs Geographic distance
23. Conclusions
24. SFE not supported in linguisticsDiscordant patterns between genetics and linguistics, with the genetic patterns all in agreement.Non-tree-like patterns in phonemic variation.(Phonemes not parallel to genes?)some correlations between distance and regions [independent of language family] – implies that pattern is, at least in part, driven by local exchange (borrowing, language contact)rates of change in language are too rapid to preserve early SFE.
25. AcknowledgementsNSF grant BCS-920114
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