Palaeodemographics of individuals in Dinaledi Chamber using dental remains

Abstract

Hominin skeletal remains from the Dinaledi Chamber, South Africa, represent a minimum of 15 individuals of the extinct species Homo naledi. We examined the dental material from this sample in order to assess the life-history stages of individuals in the sample, in particular to determine the minimum number of individuals in the sample as a whole, and within each of six age classes. We found evidence of individuals within every age class: infant, early juvenile, late juvenile, subadult, young adult and old adult. The Dinaledi Chamber sample is notable in comparison to other samples of human, chimpanzee and fossil hominins in that it has a relatively high representation of juvenile remains, as compared to infants and adults. With 15 individuals, the sample size presented by the Dinaledi dental material is too small to test the hypothesis of attritional versus catastrophic accumulation. The data here provide a basis for further investigation of individual associations within this commingled assemblage, and provide an important comparative data set as a basis for the consideration of life history in H. naledi and other extinct hominin populations. Significance:• We identified a minimum number individuals so far recovered in the assemblage and document the use of molar eruptions as biomarkers of life-history stages to sort the individuals into age classes.• We provide a demographic profile of individuals from the chamber and establish a comparative data set for life history in extinct hominin populations.

Immature remains and the first partial skeleton of a juvenile Homo naledi, a late Middle Pleistocene hominin from South Africa

“…Homo naledi age classes for 13 individuals represented in 2013-2014 excavation season, based on dentition. Two additional individuals are present based on MNI, but only approximate age can be determined: One is an adult, and one is an immature [13].…”

“…sample includes an associated partial skeleton of an adult individual, a jaw fragment from a second adult, and the remains of a very young juvenile [12]. The Dinaledi Chamber sample is much richer in fossil material, with the remains of a minimum of 15 individuals, ranging in age from neonates to older adults and dating to between 335,000 and 226,000 years ago [10,11,13,14]. The geology and taphonomy of the Dinaledi Chamber material has been described previously by Dirks et al [11].…”

“…All necessary permissions were obtained for the described study, which complied with all relevant regulations. A minimum number of individuals (MNI) was previously assessed from the 2013-2104 season based on dental remains: nine immature individuals, and six adult individuals [10,13] ( Table 2). Six of the dental individuals are either 'Infants' (deciduous dentition only) or 'Early Juveniles' (with first molars erupted).…”

“…Six of the dental individuals are either 'Infants' (deciduous dentition only) or 'Early Juveniles' (with first molars erupted). Only a single dental specimen represents a 'Late Juvenile' with second molars erupted [13] (Table 2). This 'Late Juvenile' is represented by a right mandibular fragment, U.W.…”

“…The immature individuals from the Dinaledi and Lesedi assemblages of Homo naledi represent individuals of many juvenile and adult life stages, presenting a unique opportunity to identify and document in particular a range of immature individuals of an extinct species, and contribute data to the study of comparative hominin ontogeny [10][11][12][13]. The Lesedi Chamber…”