An evolutionary model of stature, age at first birth and reproductive success in Gambian women.

We have built a model to predict optimal age at first birth for women in a natural fertility population. The only existing fully evolutionary model, based on Ache hunter-gatherers, argues that as women gain weight, their fertility (rate of giving birth) increases-thus age at first birth represents a trade-off between time allocated to weight gain and greater fertility when mature. We identify the life-history implications of female age at first birth in a Gambian population, using uniquely detailed longitudinal data collected from 1950 to date. We use height rather than weight as an indicator of growth as it is more strongly correlated with age at first birth. Stature does not greatly influence fertility in this population but has a significant effect on offspring mortality. We model age at first reproduction as a trade-off between the time spent growing and reduced infant mortality after maturation. Parameters derived from this population are fitted to show that the predicted optimal mean age of first birth, which maximizes reproductive success, is 18 years, very close to that observed. The reaction norm associated with variation in growth rate during childhood also satisfactorily predicts the variation in age at first birth.

Traitements chimiques des dyschromies dentaires : Revue systématique de la littérature

Depuis quelques années, la dentisterie esthétique suscite une attention grandissante, due à l'intérêt croissant des patients pour l'apparence esthétique de leur sourire.Un sourire éclatant est un atout sociologique, qui non seulement impacte fortement la psychologie du sujet lui-même, mais également les personnes qui l'entourent. Il est synonyme de santé.De plus, l'aspect naturel et esthétique d'une dent est déterminé non seulement par sa morphologie et sa position par rapport aux autres dents, mais aussi et surtout par sa couleur.Pour cela et face à la demande croissante des patients,il semble aujourd'hui important de s'intéresser à la valeur des différentes technique d'éclaircissement, en évaluant et en comparant leur efficacité, et surtout leur niveau d'innocuité