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Samuel PAVARD

par Pavard Samuel - publié le

Email : pavard@mnhn.fr
Phone : 01 40 79 81 62
status : teaching researcher

Reseach Team Population genetics

Research Interests

I am interested in the evolution of demographic traits (known as life history traits in ecology) and of sociality, mostly in humans. More precisely, I aim to understand the biological and cultural determinants of demographic traits ; how they vary in time and between populations ; how these demographic traits determine population dynamics in general, and thus constitute the ecological theatre in which evolutionary forces take place (mutation, migration, selection and genetic drift) ; how these demographic traits evolved in the course our species’ history. More precisely, my current research can be divided in three axis :

1. Coevolution of demographic traits and sociality in humans : the case of parental and grand parental investment – The evolution of life history traits in our species is inseparable from the evolution of social behaviours on which depends the survival and reproduction of individuals. (Grand) motherly investment in the survival of (grand) children has for example been used to explain the emergence of menopause in our species. We have for example shown the ways in which the atricial state of the human child, having probably originated from the acquisition of bipedalism, could explain the emergence of some life history traits peculiar to our species, such as human women’s capacity to give birth to a number of children during a very short reproductive period, as well as our exceptional longevity.

2. Evolution of senescence – In demography, actuarial senescence is defined as the increase of mortality with age. Evolutionary theories of senescence aim to explain why we grow old, and the factors that explain the speed at which we grow old ; may they be mechanist like the accumulation of irreversible damage with age (accumulation of reactive oxygen species, reduction of telomeres, accumulation of somatic mutations) or evolutionary (neutral or positively selected accumulation of germinal mutations involved in mortality at advanced ages). Within this context, I am interested in estimating the force of selection on alleles leading to a genetic susceptibility to illnesses occurring in later reproductive life or beyond, taking into account phenomena usually neglected by classical models in evolution of senescence ; may they be genetic (ex. Distribution in frequency of mutations) ; epidemiological (ex. Penetrance of illness by age), behavioural/cultural (ex. parental investment ; polygamy ; divorce rate, etc.).

3. ANR Sogen – From social structures to genetic structures : a genomic approach in South East Asia. I spend 33% of my time in this research project led by Dr. Raphaëlle Chaix (UMR 7206 Eco-anthropology). In the human species, evolution is not only biological but also cultural : humans invent new technologies, modify their diets, regulate their birth rate, create complex social structures, etc. Within these cultural traits, social organization interests particularly biologists because it determines when, where and with whom individuals reproduce and raise their children. Thus social organization is a key factor influencing gene transmission to the next generation as well as their dispersion between and within populations. Ethnologists have described the complexity of social organisations : union rules (that determine the choice of a partner), descent rules (that determine kinship groups) and residence rules (that determine where newlyweds must settle). This project’s objective is to understand the ways in which social organisation influence demographic traits and genetic diversity in human populations. Over the past three years, we have sampled genetic (saliva), demographic and ethnologic data in 13 populations throughout Cambodia and Laos containing a number of different social organisations (populations with patrilineal, matrilineal and cognatic affiliations with various degrees of endogamy and different residence rules). These data will allow us to : i) explore social organisation’s impact on the diversity of the neutral genome, ii) investigate which demographic traits (fertility, survival, migration) are most affected by social organisation, and iii) to develop new methodological tools for ethno genetics allowing for the analysis of given aspects of past and present social organisations.

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