The genetic architecture and evolutionary function of human scalp hair morphology

Open Access
Lasisi, Tina Tina
Graduate Program:
Doctor of Philosophy
Document Type:
Date of Defense:
April 12, 2021
Committee Members:
  • Nina G Jablonski, Dissertation Advisor/Co-Advisor
  • Nina G Jablonski, Committee Chair/Co-Chair
  • George H Perry, Committee Member
  • Tim Ryan, Major Field Member
  • Mark Shriver, Dissertation Advisor/Co-Advisor
  • Mark Shriver, Committee Chair/Co-Chair
  • William Lawrence Kenney, Jr., Outside Member
  • George Havenith, Special Member
  • Tim Ryan, Program Head/Chair
  • hair morphology
  • human evolution
  • biological anthropology
  • human scalp hair
  • human genetics
  • genetics
  • genomics
  • phenotypic variation
Most hair follicles on the human body have evolved to be miniaturized, rendering us practically ‘naked’. Despite sparse body hair, we retain thick hair on our scalps that varies significantly among populations. Yet little is known of the evolutionary history of our scalp hair and its variation. It has been suggested that scalp hair, and tightly curled hair in particular, evolved to moderate thermal load in humans. However, this functional hypothesis has never been directly tested. Existing research on human hair variation has relied on subjective and qualitative descriptors of hair morphology and samples have been historically had a strong Eurocentric bias. Despite its relevance to several evolutionary hypotheses, scalp hair has yet to be studied in a comprehensive evolutionary, functional, and genetic framework. The functional work described in this dissertation revisits the recurrent question of the role of thermoregulation in shaping early human evolution. This work is the first to extensively investigate the potential role of scalp hair and variation in its morphology in modulating heat balance in humans. More broadly, the methods, samples, and hypotheses tested in this dissertation serve to replace racialized terminology and conceptions of human scalp hair variation. Current public discussions of human biological variation demonstrate that anthropologists must continue to oppose tendencies to perceive human variation in racial terms, and focusing on hair--one of the most visible and variable human traits--will provide anthropologists with evidence of how and why variation evolved. This dissertation synthesizes methods and knowledge from various disciplines with new data, generating an innovative perspective on both human origins and modern variation and laying the foundation for future work.