Measuring fitness heritability: Life history traits versus morphological traits in humans.

ObjectivesTraditional interpretation of Fisher's Fundamental Theorem of Natural Selection is that life history traits (LHT), which are closely related with fitness, show lower heritabilities, whereas morphological traits (MT) are less related with fitness and they are expected to show higher heritabilities. In humans, although few studies have examined the heritability of LHT and MT, none of them have analyzed the same sample for comparative purposes. Here we assessed, for the first time, the heritability, additive genetic variance (V-A), residual variance (V-R) and coefficient of genetic additive variation (CVA) values of LHT and MT in a singular collection of identified skulls with associated demographic records from Hallstatt (Austria). Materials and MethodsLHT, such as lifespan, number of offspring, age at birth of first and last child, reproductive span, and lifetime reproductive success, were estimated from 18,134 individuals from the Hallstatt Catholic parish records, which represent seven generations and correspond to a time span of 400 years. MT were assessed through 17 craniofacial indices and 7 angles obtained from 355 adult crania from the same population. Heritability, V-A, V-R, and CVA values of LHT and MT were calculated using restricted maximum likelihood methods. ResultsLHT heritabilities ranged from 2.3 to 34% for the whole sample, with men showing higher heritabilities (4-45%) than women (0-23.7%). Overall, MT presented higher heritability values than most of LHT, ranging from 0 to 40.5% in craniofacial indices, and from 13.8 to 32.4% in craniofacial angles. LHT showed considerable additive genetic variance values, similar to MT, but also high environmental variance values, and most of them presenting a higher evolutionary potential than MT. DiscussionOur results demonstrate that, with the exception of lifespan, LHT show lower heritability values, than MT. The lower heritability of LHT is explained by a higher influence of environmental and cultural factors.