Le rire est un comportement humain indiscutablement universel. Abondamment traité par la psychologie et les neurosciences, il demeure néanmoins le laissé-pour-compte de l’anthropologie. Si les connaissances empiriques accumulées à ce jour ont permis de bien le caractériser à des niveaux proximaux d’analyse, la question de son origine évolutionniste est, en contrepartie, souvent évacuée. Or, toute tentative sérieuse de comprendre ce comportement requiert une investigation de sa fonction adaptative et de sa phylogénèse. Le projet entrepris ici consiste en une analyse de cinq hypothèses ultimes sur le rire et l’humour, desquelles sont extraites des prédictions qui sont confrontées à des données empiriques provenant de disciplines diverses. En guise de conclusion, il est tenté de formuler un scénario évolutif qui concilie les différentes hypothèses abordées. / Laughter is a universal and ubiquitous human behavior. Widely investigated by psychology and neuroscience, it is still largely ignored by anthropology. While humor and laughter are well caracterised at proximate levels of explanation, the question of their evolutionary origins remains relatively unexplored. A number of recent hypotheses have yet attempted to shed light on the potential adaptive significance and phylogeny of these behaviors. This project consists of an analysis of five of these ultimate explanations, by confronting their predictions to empirical data from a large array of disciplines. In the end, I propose an evolutionary framework that synthesizes and reconciles these hypotheses.

This work follows the direction set by Sewall Wright in applying path analysis, and other multivariate statistical techniques, to the study of anthropometric variation. Data on anthropometric variation of six Solomon Island populations is analyzed using statistical models which can distinguish between within-group and between-group genetic variation. The correlation structure of 27 anthropometric measurements is examined by cluster analysis and principal components analysis. The six populations show a common pattern (in both males and females) which echoes earlier studies. The correlation matrix of measurements is then partitioned into genetic and environmental components and the genetic correlation matrix is examined, once again by cluster analysis and principal components analysis. There is a fairly close agreement between the genetic correlation structure and the phenotypic correlation structure. The environmental correlation matrix is not examined further because it is very poorly estimated. The partitioning of phenotypic correlations into genetic and environmental components is based on a multivariate generalization of a path model for the heritability of a continuous trait proposed by C. C. Li. The parameters estimated in the single trait model include additive genetic heritability, common home environment, and genetic correlation between spouses. In order to fit this model observations are required on parent-offspring, spouse-spouse, and sib-sib correlations. Heritability values for the Solomons are markedly lower than those reported elsewhere. However, when total heritability (ignoring subpopulation structure) is estimated for the six Solomons populations, the values are higher and form a more familiar pattern. The striking differences between the two kinds of heritability in the Solomon Islands emphasizes the danger of using total heritability estimates obtained from several subpopulations or a national sample. The between-group component of heritability for each measurement is compared to the within-group heritability and to levels of between-group phenotypic variation. The results demonstrate that high within-group heritability for a given trait does not imply that between-group variation in that trait is genetic in origin.

This work follows the direction set by Sewall Wright in applying path analysis, and other multivariate statistical techniques, to the study of anthropometric variation. Data on anthropometric variation of six Solomon Island populations is analyzed using statistical models which can distinguish between within-group and between-group genetic variation. The correlation structure of 27 anthropometric measurements is examined by cluster analysis and principal components analysis. The six populations show a common pattern (in both males and females) which echoes earlier studies. The correlation matrix of measurements is then partitioned into genetic and environmental components and the genetic correlation matrix is examined, once again by cluster analysis and principal components analysis. There is a fairly close agreement between the genetic correlation structure and the phenotypic correlation structure. The environmental correlation matrix is not examined further because it is very poorly estimated. The partitioning of phenotypic correlations into genetic and environmental components is based on a multivariate generalization of a path model for the heritability of a continuous trait proposed by C. C. Li. The parameters estimated in the single trait model include additive genetic heritability, common home environment, and genetic correlation between spouses. In order to fit this model observations are required on parent-offspring, spouse-spouse, and sib-sib correlations. Heritability values for the Solomons are markedly lower than those reported elsewhere. However, when total heritability (ignoring subpopulation structure) is estimated for the six Solomons populations, the values are higher and form a more familiar pattern. The striking differences between the two kinds of heritability in the Solomon Islands emphasizes the danger of using total heritability estimates obtained from several subpopulations or a national sample. The between-group component of heritability for each measurement is compared to the within-group heritability and to levels of between-group phenotypic variation. The results demonstrate that high within-group heritability for a given trait does not imply that between-group variation in that trait is genetic in origin.

This work follows the direction set by Sewall Wright in applying path analysis, and other multivariate statistical techniques, to the study of anthropometric variation. Data on anthropometric variation of six Solomon Island populations is analyzed using statistical models which can distinguish between within-group and between-group genetic variation. The correlation structure of 27 anthropometric measurements is examined by cluster analysis and principal components analysis. The six populations show a common pattern (in both males and females) which echoes earlier studies. The correlation matrix of measurements is then partitioned into genetic and environmental components and the genetic correlation matrix is examined, once again by cluster analysis and principal components analysis. There is a fairly close agreement between the genetic correlation structure and the phenotypic correlation structure. The environmental correlation matrix is not examined further because it is very poorly estimated. The partitioning of phenotypic correlations into genetic and environmental components is based on a multivariate generalization of a path model for the heritability of a continuous trait proposed by C. C. Li. The parameters estimated in the single trait model include additive genetic heritability, common home environment, and genetic correlation between spouses. In order to fit this model observations are required on parent-offspring, spouse-spouse, and sib-sib correlations. Heritability values for the Solomons are markedly lower than those reported elsewhere. However, when total heritability (ignoring subpopulation structure) is estimated for the six Solomons populations, the values are higher and form a more familiar pattern. The striking differences between the two kinds of heritability in the Solomon Islands emphasizes the danger of using total heritability estimates obtained from several subpopulations or a national sample. The between-group component of heritability for each measurement is compared to the within-group heritability and to levels of between-group phenotypic variation. The results demonstrate that high within-group heritability for a given trait does not imply that between-group variation in that trait is genetic in origin.

This work follows the direction set by Sewall Wright in applying path analysis, and other multivariate statistical techniques, to the study of anthropometric variation. Data on anthropometric variation of six Solomon Island populations is analyzed using statistical models which can distinguish between within-group and between-group genetic variation. The correlation structure of 27 anthropometric measurements is examined by cluster analysis and principal components analysis. The six populations show a common pattern (in both males and females) which echoes earlier studies. The correlation matrix of measurements is then partitioned into genetic and environmental components and the genetic correlation matrix is examined, once again by cluster analysis and principal components analysis. There is a fairly close agreement between the genetic correlation structure and the phenotypic correlation structure. The environmental correlation matrix is not examined further because it is very poorly estimated. The partitioning of phenotypic correlations into genetic and environmental components is based on a multivariate generalization of a path model for the heritability of a continuous trait proposed by C. C. Li. The parameters estimated in the single trait model include additive genetic heritability, common home environment, and genetic correlation between spouses. In order to fit this model observations are required on parent-offspring, spouse-spouse, and sib-sib correlations. Heritability values for the Solomons are markedly lower than those reported elsewhere. However, when total heritability (ignoring subpopulation structure) is estimated for the six Solomons populations, the values are higher and form a more familiar pattern. The striking differences between the two kinds of heritability in the Solomon Islands emphasizes the danger of using total heritability estimates obtained from several subpopulations or a national sample. The between-group component of heritability for each measurement is compared to the within-group heritability and to levels of between-group phenotypic variation. The results demonstrate that high within-group heritability for a given trait does not imply that between-group variation in that trait is genetic in origin.

This work follows the direction set by Sewall Wright in applying path analysis, and other multivariate statistical techniques, to the study of anthropometric variation. Data on anthropometric variation of six Solomon Island populations is analyzed using statistical models which can distinguish between within-group and between-group genetic variation. The correlation structure of 27 anthropometric measurements is examined by cluster analysis and principal components analysis. The six populations show a common pattern (in both males and females) which echoes earlier studies. The correlation matrix of measurements is then partitioned into genetic and environmental components and the genetic correlation matrix is examined, once again by cluster analysis and principal components analysis. There is a fairly close agreement between the genetic correlation structure and the phenotypic correlation structure. The environmental correlation matrix is not examined further because it is very poorly estimated. The partitioning of phenotypic correlations into genetic and environmental components is based on a multivariate generalization of a path model for the heritability of a continuous trait proposed by C. C. Li. The parameters estimated in the single trait model include additive genetic heritability, common home environment, and genetic correlation between spouses. In order to fit this model observations are required on parent-offspring, spouse-spouse, and sib-sib correlations. Heritability values for the Solomons are markedly lower than those reported elsewhere. However, when total heritability (ignoring subpopulation structure) is estimated for the six Solomons populations, the values are higher and form a more familiar pattern. The striking differences between the two kinds of heritability in the Solomon Islands emphasizes the danger of using total heritability estimates obtained from several subpopulations or a national sample. The between-group component of heritability for each measurement is compared to the within-group heritability and to levels of between-group phenotypic variation. The results demonstrate that high within-group heritability for a given trait does not imply that between-group variation in that trait is genetic in origin.

L’hallux de l’humain (plus couramment appelé gros orteil) est aujourd’hui aligné avec les autres orteils ce qui rend son opposition aux autres orteils impossible. Il a été proposé que la perte de l’opposabilité de l’hallux, chez les premiers hominines, aurait mené à une augmentation des coûts liés à la maternité, due à l’obligation de transporter activement les juvéniles lors de longs trajets (Tanner & Zihlman 1976 ; Wall-Sheffler 2007 ; Watson et al. 2008). Cela suggère que l’Australopithecus afarensis devait transporter activement son juvénile car il ne pouvait pas se maintenir par lui-même lors des transports. Mon étude propose de vérifier cette hypothèse en déterminant si un primate juvénile a besoin de son hallux pour s’accrocher au poil de sa mère. Les deux hypothèses de ce travail sont donc les suivantes : L’abduction de l’hallux est nécessaire à la préhension du poil d’un porteur (généralement la mère) par les jeunes macaques et l’abduction de l’hallux n’est pas nécessaire à la préhension du poil d’un porteur (généralement la mère) par les jeunes macaques lors des transports. L’observation de vidéos de dyades mère/enfant de macaques rhésus vivant en liberté à Cayo Santiago (Costa Rica) filmées sur une période de cinq mois, tend à supporter mon hypothèse. En effet, les résultats de mon étude montrent que les macaques rhésus sont capables de s’accrocher, et se maintenir, par eux-mêmes à leur mère durant les transports sans se servir de leur hallux. Il serait cependant nécessaire de compléter cette étude par des recherches supplémentaires pour inférer avec plus de confiance ce type de comportement à l’A. afarensis. / The human hallux (more commonly called big toe) is now aligned with the other toes, which makes its opposition to other toes impossible. It has been proposed that the loss of opposability of the hallux in early hominins would have led to increase the energetic costs related to maternity, due to the obligation to carry juveniles actively (Tanner & Zihlman 1976; Wall-Sheffler 2007, Watson et al. 2008). This implies that Australopithecus afarensis juveniles had to be actively transported instead of grasping their mother's hair. My study proposes to test whether a juvenile primate needs its hallux to cling to the hair of its mother. The two hypotheses of this work are as follows: The abduction of the hallux is essential for the grasping of the hair of a carrier (usually the mother) by the young macaques and the abduction of the hallux is not necessary for the grasp of the hair of a carrier (usually the mother) by young macaques during transport. Videos of mother/child dyads of rhesus macaques are used in this study to evaluate the use of the hallux in juveniles being carried. The macaques are from a free-range colony in Cayo Santiago, Costa Rica, and they were filmed over a 5-month period. Results tend to support my hypothesis. Indeed, rhesus macaques are able to cling and maintain themselves on their mother during transport without using their hallux. It would, however, be necessary to supplement this study with further research in order to infer this type of behavior in A. afarensis.

Le remodelage osseux est un processus qui permet le renouvellement du tissu osseux tout au long de la vie des individus (Toppets et al. 2004). Il est bien connu que le remodelage est influencé à la fois par l’environnement mécanique (charges, activités) et par les besoins métaboliques (Pearson et Lieberman 2004; Rosas et Martinez-Maza 2010). Cependant, les effets des charges mécaniques sur le remodelage osseux restent encore peu compris (Lad and al. 2016; Pfeiffer and al 2006). Cette étude a pour but d’évaluer les réponses microscopiques des os aux charges mécaniques. L’échantillon étudié correspond à des paires de seconds métacarpes, issues de deux populations d’origine géographique distinctes (n=103, 55 Euro-Canadiens et 48 Inuits). À partir de section en coupe provenant de la mi-diaphyse, les lames minces ont été analysées selon quatre quadrants anatomiques : antérieur, médial, postérieur et latéral. Afin de contrôler les facteurs non mécaniques qui influencent le remodelage (tels l’âge) l’asymétrie entre les paires des métacarpes est calculée pour toutes les variables étudiées. Les charges sont estimées par les valeurs d’asymétrie de trois variables biomécaniques macroscopiques : Imax, Imin et J. Les asymétries de la densité de population des ostéons (OPD), de l’aire moyenne des ostéons et des canaux de Havers furent calculées pour estimer la réponse osseuse microscopique. De plus, il fut testé l’effet de la densité de population des ostéons sur leur aire moyenne. Les résultats démontrent que la densité d’ostéons diminue pour certains groupes (chez les hommes de St Thomas, r = - 0,412 et les femmes Inuits r = -0,547), et que les aires moyennes des ostéons et des canaux de Havers augmentent dans le quadrant antérieur du métacarpe le plus chargé (chez St-Thomas r = 0,297). De plus, il existe une relation négative entre l’augmentation de la densité d’ostéons et leur aire moyenne, dans le quadrant postérieur des femmes de St Thomas (r = -0,496). En conclusion, les charges mécaniques ont un impact sur la microstructure de l’os, rendant possible l’étude des charges à travers l’analyse histomorphologique du tissu osseux. / Bone remodeling is the process by which the skeleton can be renewed throughout the life of individuals (Toppets and al. 2004). It is well known that bone remodeling is a function of both mechanical (loads, activities) and non-mechanical factors such as metabolic needs of the bone (Pierson and Lieberman 2004; Rosas and Martinez-Maza 2010). However, the effects of mechanical environment on bone remodeling still remain poorly understood (Lad and al. 2016; Pfeiffer and al. 2006). This study aims to evaluate the microscopic bone responses to mechanical loading. The sample analyzed represents pairs of second metacarpal from two genetically separated populations (n=103, 55 Euro-Canadiens and 48 Inuits). From mid-shaft sections, thin sections were analyzed using four anatomical quadrants: anterior, medial, posterior and lateral. In order to control the influence of non-mechanical factors on bone remodeling, the asymmetry between pairs of metacarpals is calculated for each variable studied. Mechanical loading is estimated from the asymmetry values of three macroscopic biomechanical variables: Imax, Imin and J. Besides, asymmetries of osteon population density (OPD), mean areas of osteons and Havers canals were measured to estimate the microscopic bone response. Furthermore, it was tested the effect of osteon population density on osteon area. Results show that osteon population density decreases in some groups (in St-Thomas men r = - 0,412 and Inuit women r = -0,547), and the mean area of osteon and Havers canals increase in the more loaded side (in St-Thomas r = 0,297). In addition, there is a negative relationship between increased density of osteons and their mean areas in the posterior quadrant in St-Thomas women (r = -0,496). In conclusion, mechanical loading seems to have an impact on bone microstructure, making possible the inference of mechanical loadings through the study of bone histomorphology.

La masse corporelle et la direction des charges sont des facteurs qui peuvent modifier la morphologie des surfaces articulaires qui sont généralement orientées et de taille suffisante pour résister aux charges chroniques. Chez les hominoïdes, les forces de tension et compression, générées par la locomotion, sont transmises à travers l’articulation du coude. Ces espèces ont une morphologie similaire de l’extrémité distale de l’humérus, mais qui présente certaines différences selon la taille des individus et leurs modes de locomotion. Ce projet tente de caractériser plus exhaustivement cette variation en analysant la largeur des surfaces articulaires ainsi que leur position et orientation par rapport à l’axe long de la diaphyse. La prémisse de ce mémoire est que, chez les espèces plus arboricoles, la morphologie de l’articulation distale de l’humérus répond aux stress transverses générés par les puissants muscles fléchisseurs du poignet et des doigts qui traversent le coude obliquement. En revanche, les espèces plus terrestres présentent une morphologie permettant de résister aux forces axiales provenant du contact avec le sol. Des coordonnées tridimensionnelles et des mesures linéaires ont été recueillies sur un échantillon squelettique d’individus des genres Homo, Pan, Gorilla et Pongo. Les résultats obtenus révèlent que l’orientation et la position des surfaces articulaires de la trochlée correspondent aux types de locomotion, or leur taille et celle et du capitulum semblent être influencées par la taille des individus. L’hypothèse suggérant que les stress reliés aux divers modes de locomotion des hominoïdes influencent la morphologie de l’articulation distale de l’humérus est donc supportée. / In hominoids, tensile and compressive forces generated by locomotion and upper-limb use are transmitted through the elbow joint. It has been noticed that the distal humerus of hominoid is morphologically very similar across species. However, some studies have suggested that articular shape varies in relation to size and locomotor modes. This project is an attempt to characterize more thoroughly distal humeral variation in hominoids. It considers the humeral trochlea not only as a structure by itself, as it has been done before, but as an articulation that varies in orientation relative to the diaphysis. Indeed, there is evidence that articulations have a minimum size and are generally oriented to better resist habitual loads. This project tested the hypothesis that predominantly arboreal species are expected to present joints that have a size, position and orientation of articular surfaces to better resist shear loads generated by the strong finger and wrist flexor muscles crossing the elbow obliquely. Consequently, predominantly terrestrial species should present articulations shape and orientation that are better to resist axial load generated by ground reaction forces. Ten landmarks and two linear measurements were taken from a skeletal sample including specimens from the Homo, Pan, Gorilla and Pongo genus. Results show that orientation and position of humeral trochlea joint surfaces correlate with locomotor modes and that length of the articular surfaces seems to be better correlated with size. The main hypothesis suggesting that stress related to locomotion in hominoids should influence the morphology of distal humeral joints is therefore supported.

Selon certains modèles évolutionnistes, les femmes seraient davantage affectées par l’infidélité émotionnelle de leur partenaire masculin que par son infidélité sexuelle. Les mécanismes psychologiques responsables auraient évolué pendant notre passé de chasseur-cueilleur de façon à assurer à la femme un accès exclusif aux ressources économiques provenant du partenaire. Or la situation économique des femmes d’aujourd’hui a considérablement changé depuis cette époque, plusieurs d’entre-elles étant indépendantes financièrement. Dans la présente recherche, nous testons l’hypothèse que les femmes qui sont indépendantes financièrement sont moins intensément, ou moins rapidement, jalouses que les femmes qui dépendent financièrement de leur partenaire. Nous cherchons aussi à savoir si le nombre d’enfants, ou certains traits de personnalité ont une influence sur la jalousie. L’échantillon était constitué d’une soixantaine de femmes et les données proviennent de questionnaires et de mises en situation fictives. Nos résultats ne supportent pas l’hypothèse principale, les divers sous-groupes de femmes étant jalouses à la même intensité. Nous considérons divers facteurs pouvant expliquer l’absence de différences, par exemple, la possibilité que certains aspects de la relation de couple puissent cacher l’effet de la situation économique des femmes. D’autres résultats montrent une différence significative dans l’intensité de la jalousie selon l’identité de la personne en relation avec le partenaire (ancienne versus nouvelle amie). Ces résultats sont aussi évalués dans une perspective évolutionniste. / Evolutionary models propose that women are more affected by emotional infidelity than by sexual infidelity. The associated psychological mechanisms would have evolved during the hunter-gatherer phase of our phylogenetic history and would be a response to a woman’s need to secure exclusive access to the economic resources provided by her mate. The economic situation of women has changed considerably since then, many women being financially independent. In the present study we test the hypothesis that financially independent women are less intensively jealous, or become less rapidly jealous, compared to women who rely financially on their husband. We also assess whether the number of children, or certain personality traits, affect jealousy. Our sample included 60 women and the data were obtained through questionnaires featuring fictional situations. Our results do not support the main hypothesis; the various subgroups of women were jealous at comparable levels. We discuss various factors that might account for these findings, including the possibility that other aspects of the relationship might have concealed the effect of a woman’s economic situation. We also found significant differences in the intensity of jealousy according to the identity of the husband’s fictional partner (old versus new girlfriend). These results are also discussed in an evolutionary perspective.