Selection patterns driving human skull evolution: insights from quantitative genetic models.

MARTÍNEZ ABADÍAS, NEUS; MIREIA ESPARZA,; TORSTEIN SJOVOLD,; ROLANDO GONZALEZ-JOSÉ; MAURO SANTOS,; MIQUEL HERNÁNDEZ,; P KLINGENBERG, CHRISTIAN

Paris

Congreso; 8th International Congress of Vertebrate Morphology; 2007

<!-- /* Font Definitions */ @font-face {font-family:Garamond; panose-1:2 2 4 4 3 3 1 1 8 3; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:647 0 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Modern human skull morphology is the result of many evolutionary changes within the hominid lineage. Derived morphological features in Homo sapiens are a globular and expanded cranial vault, a strong cranial base flexion, and a smaller retracted face. It had long been accepted that modern human craniofacial form had evolved as an adaptive response to bipedal locomotion, to brain and sensory capsules evolution, as well as to dietary changes. However, this view is currently challenged. In this study we use quantitative genetic methods to provide insight into the genetic basis of the architecture of human skull and to test which selective forces may have driven modern human evolution. A cranial sample from Hallstatt (Austria) with 350 complete skulls falling into multigenerational pedigrees was analyzed by means of 3D geometric morphometric techniques. Skull shape was recorded as a hemicranial configuration with 28 left landmarks.  Phenotypic, additive genetic and environmental variance covariance matrices were computed following an animal model and by applying restricted maximum likelihood methods, and these were introduced at the multivariate animal breeder’s equation to simulate the response to selection. In a retrospective analysis, different selection differentials were designed in order to test the likelihood of specific adaptations (bipedalism and encephalization) being responsible for modern human skull autopomorphies. The response to selection analysis highlighted that directional selection for a larger anterior neurocranial region together with the morphological changes derived from bipedalism could have been sufficient forces to trigger human skull evolution.   Grant support: Wenner Gren Foundation for Anthropological Research (Gr. 7149), Spanish Ministerio de Educación y Ciencia, MEC-FEDER (CGL2004-00903/BTE).