This study investigates the relationship between the thermal performance of building assemblages (classes of buildings) and the social life of human communities using a multi-scalar Neo-Darwinian approach to study the evolution of the built environment. The work investigates levels of thermal operational adjustability associated with building assemblages and long-term social viability, given that social and contextual change is inevitable in the long-term. Contents: Chapter 1) Complexity, society and thermal performance; Chapter 2) Background theories: architectural studies; Chapter 3) Background theories: Archaeological studies; Chapter 4) Complexity theory and the study approach; Chapter 5) The methodology for testing for microclimate selection; Chapter 6) A global case study of generic buildings: an ethnographic sample; Chapter 7) A regional case study of buildings: long-term trends in the old world; Chapter 8) A case study of rooms in two regions: the pithouse-to-pueblo transition; Chapter 9) An urban site example: Mohenjo-Daro, Pakistan; Chapter 10) Microclimate selection in the built environment: implications.