Abstract # 236:

Scheduled for Monday, September 19, 2011 03:00 PM-03:15 PM: Session 33 (Meeting Room 410) Oral Presentation


L. Yao and R. D. Martin
The Field Museum, Department of Anthropology, 1400 S. Lake Shore Dr., Chicago, IL 60605, USA
     The Late Pleistocene LB1 specimen attributed to Homo floresiensis differs from other contemporary Homo species in South-East Asia (H. erectus, H. sapiens) in its comparatively short stature and by far the smallest endocranial volume for the genus. The proposed explanation invoked the “Island Rule”, according to which large mammals evolve to become smaller on islands to reduce resource needs. Since the Flores hominid was discovered, scientists have sought examples of brain size reduction. However, the Island Rule did not previously cover brain size. To determine whether island dwarfism applies to brain size as well as body size, volumetric and linear measurements were collected on museum skulls of pigs (Suidae, n=66), deer (Cervidae, n=69), and gibbons (Hylobatidae, n= 87), three of the most prevalent mammals endemic to South-East Asian islands and mainland areas. Scaling analysis of endocranial volume relative to body size reveals no difference between island-living mammals and mainland relatives. Island samples of adult deer and gibbons do not display significant dwarfing in brain size (p>.05). Adult pigs display a dwarfing effect in brain size (p<.001), but this is most likely influenced by extreme sexual dimorphism. Contrary to expectation, island dwarfing was absent even in body size of deer, pigs and gibbons. Thus, these results suggest that island dwarfism does not apply as a general principle explaining the tiny brain size of H. floresiensis.