Les interactions collectives, quoique récurrentes chez les microbes, sont paradoxales du point de vue de la sélection naturelle : les traits individuels qui les sous-tendent sont coûteux, donc sujets à l'exploitation de " tricheurs ". Parmi les modèles théoriques, la plupart privilégient des formalismes statiques et idéalisés, et négligent les processus physiques de formation de groupes. Dans une 1ère partie, je décris un cadre formel général pour modéliser les dynamiques évolutives d'un trait social qui augmente la propension à interagir et la cohésion des groupes. Je prouve que la meilleure agrégation des sociaux (attachement différentiel) leur suffit à s'assortir sans besoin de capacités de reconnaissance mutuelle, allégeant l'hypothèse d'attachement préférentiel fréquemment invoquée dans la littérature en l'absence de sélection de parentèle. Dans une 2nde partie, j'étaye cette preuve de principe en spécifiant un modèle computationnel d'agrégation où les individus exercent les uns sur les autres des forces d'interaction d'intensité dépendant de leur type. Je montre que l'émergence et le maintien de la socialité sont compatibles avec de tels processus de formation de groupes, en détaillant à quelles conditions sur les paramètres écologiques et microscopiques. Ce travail constitue une suggestion de scénario mécaniste pour l'évolution de la socialité au sein de groupes de taille arbitraire, ne requérant ni capacités cognitives pour les individus ni apparentement génétique. Il se veut éclairant sur les déterminants évolutionnistes de la structure sociale d'organismes tels que les dictyostélides et les myxobactéries, ainsi que sur les origines possibles de la multicellularité.

Preferences for sexual arousal by overstated dominance and submission in sex is categorized as F65.5, sadomasochism, according to ICD, but this behaviour is called BDSM among the general public. The ground of these preferences could be ultimately biological. These preferences reflect behavioural strategy which enables to gain higher reproductive success. Men and women who were sexually aroused by a submissive partner had more male relatives than men and women with other preferences. Contrary to the women, the dominant men reported themselves as more attractive. Women who were aroused by a higher-ranking partner considered themselves more attractive. Sons of couples in which was hierarchical disparity had more siblings than sons of "equal" couples or couples with no hierarchical disparity. Daughters of hierarchically disparate couples had more brothers than daughters of "both dominant" partners. Concurrently, number and gender of offspring as well as self- reported attractiveness are likely to be criteria of the reproductive success in humans. It is also interesting that hierarchically disparate couples, without regard to gender of higher-ranking partner, reached higher reproductive success than "equal" couples. Individuals who preferred higher- or lower-ranking partner were also aroused by...

Preferences for sexual arousal by overstated dominance and submission in sex is categorized as F65.5, sadomasochism, according to ICD, but this behaviour is called BDSM among the general public. The ground of these preferences could be ultimately biological. These preferences reflect behavioural strategy which enables to gain higher reproductive success. Men and women who were sexually aroused by a submissive partner had more male relatives than men and women with other preferences. Contrary to the women, the dominant men reported themselves as more attractive. Women who were aroused by a higher-ranking partner considered themselves more attractive. Sons of couples in which was hierarchical disparity had more siblings than sons of "equal" couples or couples with no hierarchical disparity. Daughters of hierarchically disparate couples had more brothers than daughters of "both dominant" partners. Concurrently, number and gender of offspring as well as self- reported attractiveness are likely to be criteria of the reproductive success in humans. It is also interesting that hierarchically disparate couples, without regard to gender of higher-ranking partner, reached higher reproductive success than "equal" couples. Individuals who preferred higher- or lower-ranking partner were also aroused by...