Evolutionary patterns of the human skull. A quantitative genetic analysis of craniofacial phenotypic variation
Year: 2007
Type: dissertation
Abstract: This thesis is the final outcome of the project "Quantitative genetics of craniofacial traits: a functional approach to heritability", which received support from the Wenner-Gren Foundation for Anthropological Research in 2004. The main goal is to integrate geometric morphometric with quantitative genetics in order to estimate the genetic variation underlying skull morphology and to assess its capability to evolve. The analyses herein are based on a sample of human skulls from Hallstatt, an Austrian village from the Alps. The uniqueness of this sample for evolutionary anthropological studies is the availability of associated genealogical data. The results show that substantial amounts of genetic variation underlying both size and shape and pervasive genetic integration are the two main aspects that characterize the genetic architecture of the human skull. The main developmental regions of the human skull (namely the face, the neurocranium and the basicranium) have similar amounts of genetic variation. There is evidence for genetic constraints, which reduce the evolutionary potential of the human skull. These correspond to shape features that can not evolve because they do not have sufficient genetic variation. The ability to evolve is restricted by complex patterns of covariation among cranial regions which direct evolution towards certain trajectories of morphological change that would maintain an operational and functional skull shape. Simulation analyses suggest a re-interpretation of the selective scenarios for human evolution. The origin of any one of the derived characters of modern humans may have facilitated the evolution of the others. The morphological changes associated with bipedalism may have enhanced the evolution of a more globular and expanded neurocranial shape, which could be favoured afterwards by selection for bigger and more complex brains. Natural selection has significantly acted over the last 200 years, since strong directional selection on skull shape and weak stabilizing selection on skull size has been detected at Hallstatt's population. However, other microevolutionary forces contributed to the evolution of skull morphology but in opposite directions, causing a non correspondence between secular trends and the response to selection patterns. The skull responds to these pressures through complex and widespread networks of genetic and epigenetic interactions.
Author: Neus Martínez Abadías
Language: Catalan
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W73819089