Francine M. Mayer

Evidence for evolution in response to natural selection in a contemporary human population

It is often claimed that modern humans have stopped evolving because cultural and technological advancements have annihilated natural selection. In contrast, recent studies show that selection can be strong in contemporary populations. However, detecting a response to selection is particularly challenging; previous evidence from wild animals has been criticized for both applying anticonservative statistical tests and failing to consider random genetic drift. Here we study life-history variation in an insular preindustrial French-Canadian population and apply a recently proposed conservative approach to testing microevolutionary responses to selection. As reported for other such societies, natural selection favored an earlier age at first reproduction (AFR) among women. AFR was also highly heritable and genetically correlated to fitness, predicting a microevolutionary change toward earlier reproduction. In agreement with this prediction, AFR declined from about 26–22 y over a 140-y period. Crucially, we uncovered a substantial change in the breeding values for this trait, indicating that the change in AFR largely occurred at the genetic level. Moreover, the genetic trend was higher than expected under the effect of random genetic drift alone. Our results show that microevolution can be detectable over relatively few generations in humans and underscore the need for studies of human demography and reproductive ecology to consider the role of evolutionary processes.

Clinical reassessment of malignant hyperthermia in Abitibi-Témiscamingue

PurposeIn 1992. 1812 individuals (1.2% of the population) were labelled at risk for malignant hyperthermia (MH) in seven families from Abitibi-Témiscamingue. To evaluate the effective risk in this population, a multidisciplinary study was undertaken which included clinical, genealogical and molecular aspects. This paper presents the clinical aspects of the study.MethodFor each of the 1546 individuals reached, all anaesthetic exposures were screened for elements relevant to MH. Malignant hyperthermia events were analyzed with “the clinical grading scale.” All 44 reports of caffeine halothane contracture tests were reappraised. Finally, a genealogical study was done to complete each family tree up to the initial French settlers in order to identify links between these seven families through common ancestors.ResultsFollowing this reassessment, the families were compared and classified into four groups. Two families (1097 individuals) are not considered to be at a higher risk for MH than the population in general. Two families are still considered possibly at rsk. Finally, one family (402 individuals) is highly at risk and two other families are probably at risk. Family trees did not show any link up to the colonization of Abitibi-Témiscamingue in the beginning of this Century but common ancestors were found around the 9th generation.ConclusionThis clinical reassessment will help to focus education and prevention on a much smaller group of individuals still considered potentially at risk for MH. By adequate evaluation of phenotypes. combined with the use of a genealogical approach, it will be possible to target families for molecular research.RésuméObjectifsEn 1992, 1812 individus (soit 1.2% de la population) étaient étiquetés comme susceptibles à l’hyperthermie maligne (HM) dans sept familles de l’Abitibi-Témiscamingue. Afin d’évaluer le risque réel de cette population, une étude multidisciplinaire fut initiée incluant les volets clinique, généalogique et moléculaire. Cet article présente les aspects cliniques de cette étude.MéthodePour chacun des 1546 individus rejoints, toutes les procédures anesthésiques furent évaluées afin de retrouver des signes révélateurs d’HM. Les épisodes d’HM furent examinés à l’aide d’une échelle de gradation clinique Les 44 rapports révisés de tests de contracture caféine-halothane furent pris en considération. Finalement, une étude généalogique de chaque ascendance, jusqu’aux premiers arrivants français, fut menée afin d’identifier les liens entre ces sept families à travers des ancêtres communs.RésultatsSuite à la révision clinique, les families furent comparées et classées en quatre groupes. Deux families (1097 individus) ne sont pas considérées plus à risque que la population en général. Deux autres families sont encore considérées comme ayant un nsque possible. Finalement, une famille (402 individus) est considérée hautement à risque et deux autres families sont classées comme ayant un nsque probable. L’examen des ascendances montre qu’on ne retrouve pas d’ancêtres communs aux cas avant la 9th génération. Ces ancêtres communs ne sont pas onginaires de la région: en effet, celle-d a été ouverte à la colonisation vers 1900 soit depuis 3–4 générations seulement.ConclusionCette révision clinique permettra de concentrer l’éducation et la prévention vers un groupe d’individus encore considéré potentiellement à nsque pour l’HM. En évaluant mieux les divers phénotypes. en combinaison avec l’utilisation d’une approche généalogique, il sera possible de cibler les meilleures families pour la recherche en génétique moléculaire.

La relation Chomage-sante: Une etude longitudinale. (Unemployment and Mental Health: A Longitudinal Analysis. With English summary.)

The cost of unemployment may be broken down into two components: economic and social costs. This paper considers one aspect of social costs: the relation between unemployment and health. It makes use of panel data collected in a survey specifically designed to analyze this relation. These data enable us to construct a validated measure of mental health. Using a fixed effects model, the authors show that the risk of deterioration of mental health is greater among the unemployed. This may generate long-term effects leading to withdrawal from the labor market and greater dependency on social welfare programs.

Eco-evolutionary dynamics in a contemporary human population

Recent studies of the joint dynamics of ecological and evolutionary processes show that changes in genotype or phenotype distributions can affect population, community and ecosystem processes. Such eco-evolutionary dynamics are likely to occur in modern humans and may influence population dynamics. Here, we study contributions to population growth from detailed genealogical records of a contemporary human population. We show that evolutionary changes in women’s age at first reproduction can affect population growth: 15.9% of variation in individual contribution to population growth over 108 years is explained by mean age at first reproduction and at least one-third of this variation (6.1%) is attributed to the genetic basis of this trait, which showed an evolutionary response to selection during the period studied. Our study suggests that eco-evolutionary processes have modulated the growth of contemporary human populations.