Friday, March 23, 2018

Morphological characteristics of the “phylogenetically primitive” Liang Bua, Flores, mandibles match past and present regional Homo sapiens populations

Robett B. Eckhardt, Sakdapong Chavanaves, Kenneth J. Hsu, and Macie J. Henneberg
AAPA 2018, Meeting Program Abstracts
April 11-14, 2018


Since the first announcement of their discovery in 2004, the bones from Liang Bua (LB), Indonesia, often have been characterized as phylogenetically primitive. However, LB bones fall into the time range for Homo sapiens, whether the original 95,000-120 ka or the revised 100,000-60,000 ka dates, and also are well within more recently-suggested ranges for our species based on 315±34 ka date for Jebel Irhoud. Within those time spans, salient morphological characteristics of the LB1 and LB6 mandibles, for example, can be matched in H. sapiens populations of the region. In extant Flores Rampasa, 93.4% have neutral or negative chins (Hastuti & Jacob, 2007). In Eastern Australian aboriginal mandibles (Larnach & Macintosh, 1971), 37.9% show negative chins; internally, a superior transverse torus ranges from slight in 47.7% to marked in 9.8%; digastric fossa ranges from slight in 37.7% to marked in 28.5%. Pertinent comparative data also are provided by the regional fossil record. At Zhirendong, South China (>100 ka), the Zhiren 3 mandible combines corpus robusticity with an inferior transverse torus lingually. From Minatogawa Fissure, Okinawa (19.9-21.8 ka), Mtg 1 exhibits a rounded external chin labially with a lingually large, deep genioglossal fossa demarcating a weak superior transverse torus from a strong inferior torus. Retromolar sulci are found in Mtg A and Mtg C, as well as in Song Keplek 5, a Holocene human skeleton from Java. Hypothetical African Plio-Pleistocene Homo ancestry for the LB hominins is unnecessary given the existence of morphologically comparable real human populations spatially and temporally closer.

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