title: Brain size of Homo floresiensis and its evolutionary implications.
abstract: The extremely small endocranial volume (ECV) of LB1, the type specimen of Homo floresiensis, poses a challenge in our understanding of human brain evolution. Some researchers hypothesize dramatic dwarfing of relative brain size from Homo erectus presumably without significant decrease in intellectual function, whereas others expect a lesser degree of brain diminution from a more primitive, small-brained form of hominin currently undocumented in eastern Asia. However, inconsistency in the published ECVs for LB1 (380-430 cc), unclear human intraspecific brain-body size scaling and other uncertainties have hampered elaborative modelling of its brain size reduction. In this study, we accurately determine the ECV of LB1 using high-resolution micro-CT scan. The ECV of LB1 thus measured, 426 cc, is larger than the commonly cited figure in previous studies (400 cc). Coupled with brain-body size correlation in Homo sapiens calculated based on a sample from 20 worldwide modern human populations, we construct new models of the brain size reduction in the evolution of H. floresiensis. The results show a more significant contribution of scaling effect than previously claimed.
authors.affiliation: Department of Biological Sciences, The University of Tokyo, , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kubo
authors.forename: Reiko T
authors.initials: RT
authors.lastname: Kono
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Kaifu
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001921:Brain / Q000033:anatomy & histology*; D005580:Fossils; D015186:Hominidae / Q000033:anatomy & histology*; D006801:Humans; D007214:Indonesia; D008954:Models, Biological; D009929:Organ Size; D012886:Skull / Q000033:anatomy & histology*; D013045:Species Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods