Presentation is loading. Please wait.

Presentation is loading. Please wait.

Genetic perspectives on prehistoric social practices Brigitte Pakendorf MPI for Evolutionary Anthropology, Leipzig, Germany.

Similar presentations


Presentation on theme: "Genetic perspectives on prehistoric social practices Brigitte Pakendorf MPI for Evolutionary Anthropology, Leipzig, Germany."— Presentation transcript:

1 Genetic perspectives on prehistoric social practices Brigitte Pakendorf MPI for Evolutionary Anthropology, Leipzig, Germany

2 Social practices and genetics? Social practices can have an effect on the number of offspring a person has  can be detected with genetic methods Holds especially true for social practices that affect one of the sexes more than the other: polygyny, residency patterns, ‘upward’ social mobility

3 Benefits of mtDNA and Y chromosome exclusively maternal and paternal inheritance, respectively no recombination

4 The benefits of studying mtDNA and Y- chromosomal markers: Y (non-sex) chromosome mtDNA Y-chromosome

5 Benefits of mtDNA and Y chromosome → mutations accumulate with time alone → possibility of defining related lineages (= haplogroups), i.e. shared mutations indicate shared ancestry (if mutations are rare!!) → complementary studies of population history (female vs male) are possible

6 Types of mutations SNPs = Single Nucleotide Polymorphisms – individual base changes (e.g. T  C): slow mutation rate STRs = Short Tandem Repeats – change in number of repeat sequence of bases (e.g. [AGCT] 16  [AGCT] 17 ): very high mutation rate

7 Socially conditioned prehistoric events 1.Residence patterns 2.Sex-biased migrations 3.Polygamy 4.‘Upward’ social mobility

8 1) Residence patterns Matrilocality: the groom settles with the wife’s family after marriage  mixing of Y- chromosomes, mtDNA’s stay put Patrilocality: the bride settles with the husband’s family after marriage  mixing of mtDNA’s, Y-chromosomes stay put Prediction: in patrilocal groups, mtDNA diversity should be higher than Y-chromosomal diversity, and vice versa for matrilocal groups

9 Oota et al. (2001) Nature Genetics 29: Genetic diversity in Thailand hill tribes

10 Melanesian mtDNA Asian mtDNA Other mtDNA 2) Sex-biased migrations: Pacific Kayser et al. (2006) Mol Biol Evol. 23: Map courtesy of the University of Texas Libraries, The University of Texas at Austin.

11 Melanesian Y-DNA Asian Y-DNA Other Y-DNA 2) Sex-biased migrations: Pacific Kayser et al. (2006) Mol Biol Evol. 23: Map courtesy of the University of Texas Libraries, The University of Texas at Austin.

12 Polynesian mtDNA: 94% Asian origin 2) Sex-biased migrations: Pacific Polynesian Y: 66% Melanesian origin  Potentially due to matrilocality of Austronesian- speakers  Melanesian men incorporated into Austronesian- speaking society prior to further migration to Polynesia Kayser et al. (2006) Mol Biol Evol. 23:

13 2) Sex-biased migrations: male conquerors Closely-related Y-chromosomal lineage identified in 16 Central Asian populations Zerjal et al. (2003): Am J Hum Gen. 72: 717–721

14 2) Sex-biased migrations: male conquerors Zerjal et al. (2003): Am J Hum Gen. 72: 717–721

15 2) Sex-biased migrations: male conquerors Closely-related Y-chromosomal lineage identified in 16 Central Asian populations Dated to ~ years BP Most likely origin in Mongolia (highest diversity) Zerjal et al. (2003): Am J Hum Gen. 72: 717–721

16 2) Sex-biased migrations: male conquerors Distribution of Mongolian Y-chromosomal lineage; shaded area = extent of Mongol Empire at time of Chinggis Khan’s death Zerjal et al. (2003): Am J Hum Gen. 72: 717–721

17 2) Sex-biased migrations: male conquerors Y-lineage with one male ancestor ~ 1000 years ago widespread in Central Asia  spread with Mongol Empire ruling clans = Chinggis Khan’s sons and grandsons  ‘Chinggis Khan’s Y-chromosome’ Zerjal et al. (2003): Am J Hum Gen. 72: 717–721

18 3) Polygamy (polygyny) Polygyny: few men have many wives, and many men may have no wife at all Prediction: (severely) reduced Y-chromosomal diversity

19 Kayser et al. (2003): Am J Hum Genet 72: Y-chromosomal SNP frequencies in New Guinea

20 Y-chromosomal and mtDNA diversity, West New Guinea Group (N Y/ N mtDNA) Y-SNP diversity Y-STR diversity HVR1 diversity Dani (12/21).167 ± ± ±.02 Una (46/50)0.749 ± ±.01 Ketengban (19/22) ± ±.07 Citak (28/39).267 ± ± ±.03 Kayser et al. (2003): Am J Hum Genet 72:

21 Social practices of Bantu-speaking groups? Can genetic studies inform us about the prehistoric social practices of Bantu-speaking groups (intermarriage with hunter-gathering populations, patrilocality)?

22 Upward social mobility Ethnographic assumption: agriculturalist men may marry hunter-gatherer women, but not vice versa Prediction: introgression of ‘hunter-gatherer mtDNA’ but not Y-chromosomes in agricultural populations

23 Upward social mobility ‘Khoisan-specific’ haplogroups mtDNA L0dY-chr. A-M51 Southern African Bantu speakers Southern African Bantu-speakers

24 Upward social mobility ‘Khoisan-specific’ haplogroups mtDNA L0dY-chr. A-M51 Southern African Bantu speakers 4-7% Southern African Bantu-speakers Pereira et al. (2001): Ann Hum Genet 65: Salas et al. (2002): Am J Hum Genet. 71: 1082–1111

25 Upward social mobility ‘Khoisan-specific’ haplogroups mtDNA L0dY-chr. A-M51 Southern African Bantu speakers 4-7% Southern African Bantu-speakers 3-7% Pereira et al. (2001): Ann Hum Genet 65: Salas et al. (2002): Am J Hum Genet. 71: 1082–1111 Wood et al. (2005): Eur J Hum Genet 13:

26 Upward social mobility Potentially intriguing finding: 1) the social ideal is not always adhered to 2) shift of language and identity of small groups of Khoisan-speakers in Southern Africa

27 Upward social mobility ‘Khoisan-specific’ haplogroups mtDNA L0dY-chr. A-M51 Southern African Bantu speakers 4-7% Southern African Bantu-speakers 3-7% Pereira et al. (2001): Ann Hum Genet 65: Salas et al. (2002): Am J Hum Genet. 71: 1082–1111 Wood et al. (2005): Eur J Hum Genet 13:

28 Upward social mobility ‘Khoisan-specific’ haplogroups mtDNA L0dY-chr. A-M51 Mozambique Bantu speakers 4-7%?? South Africa Bantu-speakers ??3-7% Pereira et al. (2001): Ann Hum Genet 65: Salas et al. (2002): Am J Hum Genet. 71: 1082–1111 Wood et al. (2005): Eur J Hum Genet 13:

29 Upward social mobility Caveat: groups not really comparable  South African Nguni populations (Zulus, Xhosa) are known to have been in close contact with Khoisan speakers (‘borrowing’ of clicks)

30 Patrilocality in Bantu-speakers? Prediction: in patrilocal groups, mtDNA diversity should be higher than Y-chromosomal diversity

31 Haplogroup diversity values in some Bantu-speaking groups Tishkoff et al. (2007): Mol Biol Evol 24: ; Pereira et al. (2001): Ann Hum Genet 65: Salas et al. (2002): Am J Hum Genet. 71: 1082–1111; Wood et al. (2005): Eur J Hum Genet 13: Quintana-Murci et al. (2008): PNAS 105: 1596–1601; De Filippo et al. unpublished

32 Social practices of Bantu-speaking groups? Reduced Y-chromosomal diversity appears indicative of patrilocal post-marital residence

33 Data are not comparable ‘West Central Africa’ mtDNA = 20 groups from Cameroon and Gabon Y-chromosome = 3 groups from Cameroon ‘Southern Africa’ mtDNA = ~ 20 different populations from Mozambique Y-chromosome = Sotho-Tswana, Zulu and Xhosa from South Africa

34 Data are not comparable practically no comparable data available for mtDNA and Y-chromosome in the same Bantu- speaking groups

35 Conclusions Genetic analyses can provide some insights into prehistoric social practices These may be of help for historical linguists in search of explanations for patterns of linguistic diversity (e.g. contact-induced change) However, comparable studies of both mtDNA and Y-chromosomal diversity in ethno- linguistically well-defined groups are needed

36 Acknowledgements Cesare de Filippo for Bisa and Kunda data Mark Stoneking for discussion


Download ppt "Genetic perspectives on prehistoric social practices Brigitte Pakendorf MPI for Evolutionary Anthropology, Leipzig, Germany."

Similar presentations


Ads by Google