Are we using the appropriate reference samples to develop juvenile age estimation methods based on bone size? An exploration of growth differences between average children and those who become victims of homicide

A c o m p a r a t i ve g r o w t h a n a l y s i s o f A f r i c a n c h i l d t h t h s l av e s i n 1 5 to 17 c e n t u r y Po r t u g a l Laure Spake1 ; Maria Teresa Ferreira2 ; Sofia Wasterlain2 ; and Hugo F.V. Cardoso1 1 Department of Archaeology, Centre for Forensic Research, Simon Fraser University; 2 Department of Life Sciences, Centro de Ecologia Funcional, Centro de Investigação em Antropologia e Saúde, University of Coimbra hcardoso@sfu.ca INTRODUCTION RESULTS A 2009 salvage excavation in Lagos, Portugal (Figure 1), unearthed human remains from two sites located outside of the medieval city walls. One of these yielded 158 remains buried in an urban waste deposit (Figure 2). Evidence including burial goods, morphoscopic analyses, and genetic analyses, suggests that this was an African slave burial site [1-3]. While the Trans-Atlantic slave trade has been well studied, this is not the case for the slave trade to Europe, which reached Portugal, Spain, Britain, and France. The lives of African enslaved peoples in Europe is poorly understood. This assemblage includes 23 juvenile individuals. As growth is highly responsive to environmental stressors, understanding the growth of these individuals can shed light on the conditions of life of enslaved Africans in Europe. To this end, we compare the Lagos juveniles to documented juveniles from the US and South Africa whose socioeconomic contexts and growth environment are known. 8 5 T H A N N UA L M E E T I N G O F T H E A M E R I C A N A S S O C I AT I O N O F P H Y S I C A L A N T H R O P O LO G I S T S – A T L A N TA , G A , A P R I L 1 2 - 16 2 016 Figure 1. Location of Lagos within Portugal and the Iberian Peninsula The SGPs showed that of the comparative samples, the Raymond Dart was the smallest for age, followed by the Hamann-Todd (Figure 4). The SALB sample was the largest for age. The Lagos sample equivocated well with the Raymond Dart and Hamann-Todd samples, but was consistently shorter for age than the SALB sample The ANCOVA analyses showed slightly different trends between children under and over 2 years of age (Table 1). In children <2 years, the Lagos, Hamann-Todd, and Raymond Dart samples never differed from each other while the SALB sample always did. In children ≥2 years, the SALB sample remains significantly larger for age than all other samples. The Hamann-Todd sample is now larger than the Raymond Dart sample, sometimes significantly so. In this group, the Lagos sample aligns more closely with the Raymond Dart rather than the Hamann-Todd sample. Figure 2. Burial position of Individual 6. Individuals were not buried in accordance with contemporary patterns MATERIALS AND METHODS All juveniles who had not commenced skeletal fusion and for whom teeth could be measured were selected. This yielded a sample of 20 individuals. Maximum tooth length was measured either directly or using radiographs (Figure 3) as specified by Liversidge et al [4]. Age was estimated from the length of each available tooth excluding the third molar using formulae provided by Liversidge and colleagues [4.5], which were averaged together to obtain a final age estimate. Skeletal growth profiles (SGPs) were constructed from diaphyseal lengths of the humerus, radius, femur, and tibia using three comparative samples: 1. Raymond Dart Collection – 29 black children aged 0.16-12.50 years from South Africa; unclaimed bodies collected between 1920 and 1958. 2. Hamann-Todd Collection – 20 black children aged 1.14-11.50 years from the U.S.; unclaimed bodies of children dying in hospitals between 1919 and 1931. 3. South African Long Bone Database – 408 black children aged 0.10-12.70 years from South Africa; mix of cadaveric radiographs and hospital Lodox scans, collected by Dr. Kyra Stull between 2007 and 2012. Figure 4. Comparison of the Lagos (green), Dart (yellow), Hamann-Todd (orange), and South African Long Bone (SALB, red) samples. Plots illustrate long bone length for age for the humerus (top left); radius (bottom left); femur (top right); and tibia (bottom right) Table 1. ANCOVA p-values for differences between Lagos and each comparative sample, for the each bone, for children under and above 2 years of age Dart Hamann-Todd SALB ANCOVAs were conducted to quantify differences in growth between the samples. This was done separately for children under and over 2 years of age, to account for the differences in growth velocity in infants versus pre-pubertal children. Humerus Radius Femur Tibia <2 years 0.77 0.77 0.52 0.77 ≥2 years 0.95 0.47 0.67 0.92 <2 years 0.54 0.50 0.82 0.62 ≥2 years 0.02 0.27 0.15 0.01 <2 years 0.01 0.05 0.00 0.00 ≥2 years 0.00 0.00 0.00 0.00 DISCUSSION In younger children, the Lagos sample resembles both the Hamann-Todd and the Raymond Dart samples. In the older children, the Lagos sample more closely resembles the Dart sample. The modern SALB children are significantly larger than other samples at all ages. The Dart children lived in early 20th century, a difficult time for black South Africans [6]. They were exposed to malnutrition, racial discrimination, and poor living conditions. The congruence between the Lagos and Dart children suggests that the Lagos children were under considerable stress, however it is unclear whether this is due to the passage from Africa or to excessive workloads and poor nutrition after arrival. While there is evidence that slaves in the United States were well fed [7], this was not the case here. Figure 3. Measurements of isolated teeth (left), and dental radiographs (center), as a maximum length following the axis of the tooth. Diaphysis of the femur (right). Further, the differences in growth between the samples, given that they are all of African ancestry, suggests that environmental, not genetic, factors are the primary driver in growth. WORKS CITED 1. Wasterlain SN, Neves MJ, Ferreira MT. 2016. Dental modifications in a skeletal sample of enslaved Africans found at Lagos (Portugal). Int J Osteoarchaeol 26:621-632. 2. Coelho C, Navega D, Cunha E, Ferreira MT, Wasterlain SN. 2016. Ancestry estimation based on morphoscopic traits in a sample of African slaves from Lagos, Portugal. Int J Osteoarchaeol in press. 3. Martiano R, Coelho C, Ferreira MT, Neves MJ, Pinhasi R, Bradley DG. 2014. Genetic evidence of African slavery at the beginning of the Trans-Atlantic slave trade. Scientific Reports 4:5994. 4. Liversidge HM, Dean MC, Molleson TI. 1993. Increasing human tooth length between birth and 5.4 years. Am J Phys Anthropol 90(3):307-313. 5. Liversidge HM, Molleson Ti. 1999. Developing permanent tooth length as an estimate of age. J Forensic Sci 44(5):917-920. 6. Cameron N, Tobias PV, Fraser WJ, Nagdee M. 1990. Search for secular trands in calvarial diameters, cranial base height, indices, and capacity in South African Negro Crania. Am J Hum Biol 2:53-61. 7. Steckel RH. 1979. Slave height profiles from coastwise manifests. Explor Econ Hist 16:363-380.