“Small Size” in the Philippine Human Fossil Record: Is it Meaningful for a Better Understanding of the Evolutionary History of the Negritos?

Abstract

Abstract"Pygmy populations" are recognized in several places over the world, especially in Western Africa and in Southeast Asia (Philippine "negritos," for instance). Broadly defined as "small-bodied Homo sapiens" (compared with neighboring populations), their origins and the nature of the processes involved in the maintenance of their phenotype over time are highly debated. Major results have been recently obtained from population genetics on present-day negrito populations, but their evolutionary history remains largely unresolved. We present and discuss the Upper Pleistocene human remains recovered from Tabon Cave and Callao Cave in the Philippines, which are potentially highly relevant to these research questions. Human fossils have been recovered in large numbers from Tabon Cave (Palawan Island) but mainly from reworked and mixed sediments from several archaeological layers. We review and synthesize the long and meticulous collaborative work done on the archives left from the 1960s excavations and on the field. The results demonstrate the long history of human occupations in the cave, since at least ~30,000 BP. The examination of the Tabon human remains shows a large variability: large and robust for one part of the sample, and small and gracile for the other part. The latter would fit quite comfortably within the range of variation of Philippine negritos. Farther north, on Luzon Island, the human third metatarsal recently recovered from Callao Cave and dated to ~66,000 BP is now the oldest direct evidence of human presence in the Philippines. Previous data show that, compared with H. sapiens (including Philippine negritos), this bone presents a very small size and several unusual morphological characteristics. We present a new analytical approach using three-dimensional geometric morphometrics for comparing the Callao fossil to a wide array of extant Asian mammals, including nonhuman primates and H. sapiens. The results demonstrate that the shape of the Callao metatarsal is definitely closer to humans than to any other groups. The fossil clearly belongs to the genus Homo; however, it remains at the margin of the variation range of H. sapiens. Because of its great antiquity and the presence of another diminutive species of the genus Homo in the Wallace area during this time period (H. floresiensis), we discuss here in detail the affinities and potential relatedness of the Callao fossil with negritos that are found today on Luzon Island. Abstract "Pygmy populations" are recognized in several places over the world, especially in Western Africa and in Southeast Asia (Philippine "negritos," for instance). Broadly defined as "small-bodied Homo sapiens" (compared with neighboring populations), their origins and the nature of the processes involved in the maintenance of their phenotype over time are highly debated. Major results have been recently obtained from population genetics on present-day negrito populations, but their evolutionary history remains largely unresolved. We present and discuss the Upper Pleisto...

Deep Skull from Niah Cave and the Pleistocene Peopling of Southeast Asia

“…All of this further suggests that the morphologically robustly built Late Pleistocene people of Southeast and East Asia, widely considered to represent a population related to Australo-Melanesians (e.g., Bellwood, 1997;Matsumura and Hudson, 2005;Matsumura et al, 2008;Oxenham and Buckley, 2016), were probably more restricted in their geographic distribution than has been proposed until now. Our study suggests the twolayer hypothesis is unlikely to apply to the earliest inhabitants of Borneo, in-line with genetic research, and as proposed recently also for Pleistocene human remains described from the Philippines (Détroit et al, 2013).…”

“…(1) The Niah individual samples a population related (?ancestral) to some of the contemporary indigenous people of Borneo (as proposed by Harrisson, 1976). (2) The Deep Skull represents a Negrito group (see also Birdsell, 1978), and although this term has considerable ambiguity historically in the literature (Endicott, 2013), we apply it in a restricted sense to refer to a gracile and small statured population probably related to the people inhabiting the Philippines today and apparently also during the Pleistocene (Détroit et al, 2013). Both of these conclusions receive support from the partial femur recovered along with the Deep Skull (Harrisson, 1967), with its short reconstructed length (c370 mm) and diminutive estimated stature (c4.5 feet or c137 cm: Krigbaum and Datan, 2005).…”

Tropical forests and the genus Homo

“…These environmental characteristics are not exclusive and may all contribute to phenotypic convergence of small body sizes in rainforest environments. [Color figure can be viewed at wileyonlinelibrary.com] Callao Cave, c. 66 ka, 115 though this remains contentious. Other evidence, such as the early genetic divergence of rainforest hunter-gatherers from their current nearest neighbors, as well as the genetic isolation of pygmy groups in Africa as a result of forest fragmentation and expansion, further highlights the potential role tropical forests may have played as evolutionary "islands" in the evolution of human phenotypes.…”

Contrasting maternal and paternal genetic variation of hunter-gatherer groups in Thailand

“…The phenotypic resemblances of SEA negritos and African pygmies initially suggested a separate origin in Africa, although convergent evolution now seems more likely (for reviews see Détroit et al . 3 and Stock 4 ). Hunting-gathering was the mode of subsistence traditionally practiced by most SEA negritos, whose communities are distributed in three regions: Andaman Islands, Peninsular Thailand and Malaysia, and the Philippines 5 .…”