title: Anatomical network analysis shows decoupling of modular lability and complexity in the evolution of the primate skull.
abstract: Modularity and complexity go hand in hand in the evolution of the skull of primates. Because analyses of these two parameters often use different approaches, we do not know yet how modularity evolves within, or as a consequence of, an also-evolving complex organization. Here we use a novel network theory-based approach (Anatomical Network Analysis) to assess how the organization of skull bones constrains the co-evolution of modularity and complexity among primates. We used the pattern of bone contacts modeled as networks to identify connectivity modules and quantify morphological complexity. We analyzed whether modularity and complexity evolved coordinately in the skull of primates. Specifically, we tested Herbert Simon's general theory of near-decomposability, which states that modularity promotes the evolution of complexity. We found that the skulls of extant primates divide into one conserved cranial module and up to three labile facial modules, whose composition varies among primates. Despite changes in modularity, statistical analyses reject a positive feedback between modularity and complexity. Our results suggest a decoupling of complexity and modularity that translates to varying levels of constraint on the morphological evolvability of the primate skull. This study has methodological and conceptual implications for grasping the constraints that underlie the developmental and functional integration of the skull of humans and other primates.
authors.affiliation: Theoretical Biology Research Group, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, 46071, Valencia, Spain; Department of Anatomy, Howard University College of Medicine, Washington, DC, United States of America.
authors.forename: Borja
authors.initials: B
authors.lastname: Esteve-Altava
authors.affiliation: Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK, Canada.
authors.forename: Julia C
authors.initials: JC
authors.lastname: Boughner
authors.affiliation: Department of Anatomy, Howard University College of Medicine, Washington, DC, United States of America.
authors.forename: Rui
authors.initials: R
authors.lastname: Diogo
authors.affiliation: Department of Anthropology, University of Nevada Las Vegas, Las Vegas, NV, United States of America; Department of Anthropology, University College London, London, United Kingdom.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Villmoare
authors.affiliation: Theoretical Biology Research Group, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, 46071, Valencia, Spain.
authors.forename: Diego
authors.initials: D
authors.lastname: Rasskin-Gutman
mesh_terms: D000818:Animals; D005075:Biological Evolution; D010802:Phylogeny; D011323:Primates / Q000033:anatomy & histology* / Q000145:classification; D012886:Skull / Q000033:anatomy & histology*