The Application of Statistics in Addressing the Position of Homo Floresiensis in Human Evolution

• Activity Number: 46
• Type: Other
• Date/Time: Sunday, August 1, 2010 : 4:00 PM to 5:50 PM
• Sponsor: ASA
• Author(s): Karen Baab*+
• Companies: Stony Brook University Medical Center

Abstract

Recovered deep in Late Pleistocene sediments (~95,000 - 15,000 years ago) within a remote limestone cave on the isolated island of Flores in the Indonesian archipelago, the barely fossilized remains of several individuals served as the basis for recognizing the newest species of our own genus Homo: Homo floresiensis. Since their intial description in 2004, the interpretation of these fossils has been the subject of heated controversy. Although fossils of several Homo floresiensis individuals were recovered, it is the type specimen (LB1) that is truly extraordinary for its degree of completeness. It is a very rare opportunity to be able to study skulls and postcrania (limb bones, bony girdles, etc.) from the same individual in the fossil record, and we now possess a wealth of integrated information on the cranium, brain, jaw, arms, legs, hands and feet of the hobbits. We quantified and analyzed the shape of the LB1 skull using three-dimensional landmarks. Principal component analysis indicate that the shape of the LB1 skull is more similar to extinct human ancestors than to either healthy or pathological modern humans. Even taking the very small size of the Homo floresiensis skull into account, the strongest affinities are with fossil rather than modern humans. Its also apparent that asymmetry in skull shape is within the range of living apes as well as other fossil humans, which argues against pathological asymmetry. Based on linear measurements of the skeleton, we can also show that LB1 had absolutely and relatively shorter legs than any modern human population; this creates an upper to lower limb ratio never observed in people. It also results in a relatively very long (and surprisingly primitive) foot. We estimated both height and mass in this individual using regression analysis, which demonstrates that Homo floresiensis had a very non-human body shape - one which in which a relatively large mass is distributed over a small skeletal frame, similar to fossil humans more than 3 million years old.