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The CECD is an AHRC funded research group dedicated to examining the evolutionary underpinnings of human cultural behaviour, past and present. more>

Page Title - projects
Phase 2: Continuing CEACB projects (phase 1): Project 036
Modelling cultural evolution in Indo-European groups


Laura Fortunato (Santa Fe Institute)

UCL Graduate School Scholarship for Cross-Disciplinary Training (2006-07);
UCL Graduate School Research Scholarship (2004-07, suspended 2006-07, resumed 2007-08);
ESRC 1 + 3 Research Studentship (2003-07, suspended 2006-07, resumed 2007-08);
University of Padova, Faculties of Science and Engineering Fondazione Gini Award (2003-04; 2004-05). Cards Against Humanity
fridge freezers

Kinship and marriage systems represent the ways in which humans organize relatedness and reproduction. This project extends the philosophical, theoretical, and methodological foundations of evolutionary biology to the study of these aspects of human social behaviour. Foci of the project include:

1. a game-theoretic analysis showing that the evolution of monogamous marriage can be understood within the framework of inclusive fitness theory.

2. phylogenetic comparative analyses of wealth transfer, marriage, and residence strategies across societies speaking Indo-European languages; these analyses reconstruct early Indo-European society as practising dowry, monogamy, and prevailing virilocality with alternative neolocality.

3. development of the Ethnographic Database Project ( to complement and improve upon existing cross-cultural databases, using a web-based interface for the collection and standardisation of cross-cultural data.

Kinship and marriage systems represent the ways in which humans organize relatedness and reproduction. This project investigated how evolution has shaped kinship and marriage systems and how these, in turn, have shaped human social behaviour. The study of the human family has been a traditional focus of anthropology; however, theoretical and methodological difficulties let do its abandonment during the second half of the twentieth century. Evolutionary biology offers a unified conceptual and analytical framework to overcome these difficulties. In turn, to the extent that networks based on kinship and marriage created the social niche in which our species evolved, understanding their workings becomes crucial for understanding the evolution of human behaviour. The work carried out as part of this project combines anthropological theory and data with theoretical and statistical methods used in the study of non-human social systems.

For example, in collaboration with Marco Archetti (Zoology, University of Oxford), I have used inclusive fitness analysis in a game-theoretic framework to model the co-evolution of marriage and inheritance strategies, and their interactions with subsistence system, female contribution to production, and level of paternity. This work investigates why some societies prescribe monogamous marriage while the majority allow polygyny. It shows that where resources are transferred across generations, social monogamy can be advantageous because it "concentrates" wealth in a limited number of heirs, and because females are likely to grant higher fidelity to husbands who invest exclusively in their offspring. This may explain why monogamous marriage prevailed among societies of Europe and Asia practising intensive agriculture, and why it first emerged in these regions: here land was limited, and the partitioning of estates depleted their value. Consistently, cultural norms promoting high paternity, such as ideologies of virginity and sexual fidelity, were common in these societies. This work is described in Fortunato L & Archetti M, J. Evolution. Biol. 23 (2010): 149–156.

Second, I have used phylogenetic comparative methods to reconstruct the pattern of change in kinship and marriage practices, and to test hypotheses about their evolution. This provides insights into features of social organization that are not preserved in the archaeological or historical records. For example, I have used Bayesian Markov chain Monte Carlo methods to infer the posterior probability distributions of different modes of marital residence (patri-, neo-, and matrilocality) in Proto-Indo-European society. This analysis used cross-cultural data on marital residence for societies speaking Indo-European languages; a posterior probability sample of phylogenetic trees, obtained from linguistic data by Mark Pagel and colleagues (Biology, University of Reading), served as a model of the historical relationships among these societies. Marital residence customs regulate the movement of people between groups, thereby shaping the pattern (1) of genetic variation across populations and (2) of co-operation and competition among relatives within groups. Consequently, knowledge of this aspect of social organization is crucial for understanding (1) the demographic history of our species and (2) the effect of differential access to kin in the evolution of our species’ social behaviour. This work is described in Fortunato L & Jordan FM, Philos. T. Roy. Soc. B. (2010, in press) and Fortunato L, Hum. Biol. (2011, in press).

Fortunato, L (2011).
Reconstructing the history of residence strategies in Indo-European-speaking societies: neo-, uxori-, and virilocality. Human Biology. Vol 83:107-128.
Fortunato, L. & Jordan, F.M (2010).
Your place or mine? A phylogenetic comparative analysis of postmarital residence in Indo-European and Austronesian societies. Phil. Trans. R. Soc. Lond. B.
Fortunato, L. & Archetti, M (2010).
Evolution of monogamous marriage by maximization of inclusive fitness. Journal of Evolutionary Biology. Vol 23(1):149-156.
Fortunato, L. and R. Mace (2009).
Testing functional hypotheses about cross-cultural variation: a maximum-likelihood comparative analysis of Indo-European marriage practices. In: S. J. Shennan (ed.) (ed\s) Pattern and Process in Cultural Evolution. University of California Press. 235-249.
Fortunato, L (2008).
A phylogenetic approach to the history of cultural practices. In: Allen, N. J., Callan, H., Dunbar, R. & James, W. (eds.) (ed\s) Early human kinship: from sex to social reproduction. Blackwell Publishing Ltd.: Malden, MA. 189-199.
Fortunato, L (2007).
Beyond the Ethnographic Atlas: cross-cultural data and the comparative analysis of human cultural practices. EHBES 2007 Conference.
Fortunato, L., C. J. Holden and R. Mace (2006).
From bridewealth to dowry? A Bayesian estimation of ancestral states of marriage transfers in Indo-European groups . Human Nature . Vol 17(4):355-376.