The human remains from Songo Mnara, Tanzania Season. Kate Robson Brown and Francesca Migliaccio

Transcription

1 The human remains from Songo Mnara, Tanzania Season. Kate Robson Brown and Francesca Migliaccio March

2 Contents Contents... 2 List of Tables... 3 List of Figures... 4 Introduction... 4 Methods... 6 Results... 8 Preservation... 9 Demography... 9 Metrics and non-metrics Metrics Non-metrics The Dentition Dental health Congenital anomalies Palaeopathology Infectious Disease Degenerative joint disease Metabolic disease Neoplastic disease Congenital anomalies Discussion References Cited Contents [Songo Mnara 2011]

3 List of Tables Table 1: Sub-adult ages Table 2: Adult age and sex Table 3: Estimated stature of the adults Table 4: Cranial non-metric traits present Table 5: Dentitions, ante-mortem tooth loss and caries by age and sex.19 Table 6: Enamel hypoplasia, abscess and periodontal disease presence 19 Table 7: Caries and enamel hypoplasia presence by teeth scored.20 Table 8: Calculus presence by teeth scored.20 Table 9: Osteoarthritis by side in the appendicular skeleton..23 Table 10: Skeletons with osteoarthritis 25 Table 11: Incidence of Cribra Orbitalia 26 3 List of Tables [Songo Mnara 2011]

4 List of Figures Figure 1: Abscess and periodontal disease in a young male SK Figure 2: Osteoarthritis in the right shoulder; osteophyte formation and pitting in the right clavicle (SK 3).23 Figure 3: Osteoarthritis in the right shoulder; osteophyte formation and pitting in the right glenoid fossa (SK 3) 24 Figure 4: Osteoarthritis in the spine with Schmorl s nodes (SK 4) 25 Figure 6: Cribra Orbitalia in the right orbit (SK 9).27 Figure 7: Spina bifida in the sacrum of SK List of Figures [Songo Mnara 2011]

5 Introduction In 2011 a series of three pilot excavations were undertaken in the cemeteries of Songo Mnara, a Swahili stonetown on the southern coast of Tanzania. A World Heritage Site, Songo Mnara is recognized as the most impressive of all Swahili townscapes and considered to be the quintessential expression of the coral-built tradition for which the coastal towns became famous. The town has a full range of domestic and non-domestic structures, with more than 40 coral-built houses and room-blocks, 5 mosques and multiple cemeteries. Occupation of the site was brief, from the 14th to 16th centuries AD, coinciding with the golden age of Swahili stonetowns along the coast. The sensitive nature of African, Islamic, archaeological burials renders excavation and study of such remains extremely rare. This collection therefore provides a unique opportunity to explore issues such as the relationship between demography, ethnicity, and spatial arrangement of inhumations. This analysis will provide important data to help us understand the overall meaning attached to the central open space: whether the ritual nature of the space was aimed at establishing power and status through the interment of town leaders (i.e., burials of elderly men), or whether the burial ground represented more general representation of the settlement s inhabitants, with clusters perhaps representing family or clan groups. In summary, the purpose of this pilot osteoarchaeological study was to evaluate: a) The state of preservation of human remains across the cemetery areas. b) The relationship between funerary architecture and burial characteristics. c) Where appropriate, the age, sex, ethnicity and health status of the exhumed remains. 5 Introduction [Songo Mnara 2011]

6 d) The potential of the site for further excavation and osteoarchaeological investigation. During the course of the 2011 summer excavation season, the remains of 14 individuals were identified and exhumed from 4 trenches sampling different burial contexts. The material was cleaned and reported on site, and reinterred in correct anatomical position during the excavation. Methods The information recorded for each individual skeleton, included: preservation, age at death, sex of the individual, metric and non-metric data including measurements taken as part of an assessment of skeletal ethnicity, and evidence for palaeopathology. Each skeleton was recorded on a separate recording form and this information will be entered into a database to be kept with the archive. Preservation was recorded as excellent, good, fair or poor and the percentage of the skeleton present was recorded as <25%, 25-50%, 50-75% or >75% complete. Surface erosion was scored according to McKinley (2004, 16). The sub-adults were aged by dental formation and eruption and epiphyseal fusion. The tooth formation stages of Moorrees et al. (1963a, 1963b) as modified by Smith (1991) were used where possible along with the dental eruption chart of Schour & Massler (1941). Epiphyseal fusion and ossification age stages were obtained from Scheuer & Black (2000). Whereas sub-adult ageing can be fairly precise if the dentition is present, due to the development of the dentition taking place gradually from before birth until late adolescence, the ageing of adults relies on degenerative changes to the skeleton which will be less precise. The methods of ageing used for each adult skeleton (where possible) were dental attrition (Brothwell 1981), age related changes of the pubic symphysis following the Suchey-Brooks method (as 6 Methods [Songo Mnara 2011]

7 cited in Buikstra & Ubelaker 1994), age related changes of the auricular surface of the os coxae using the method of Meindl and Lovejoy (as cited in Buikstra & Ubelaker 1994), cranial suture closure using the method of Meindl & Lovejoy (as cited in Buikstra & Ubelaker 1994) and age related changes to the sternal rib ends using the method of Iscan (as cited in Bass 1995). Each adult skeleton was placed into one of three adult age categories: young adult years; middle aged adult years; and old adult 50+ years. Assigning sex to adult skeletons is relatively straight forward when the most sexually dimorphic elements of the skeleton are present such as the pelvic bones, skull and mandible (Mays 1998; Schwartz 1995; Buikstra & Ubelaker 1994; Brothwell 1981). When these are not present it is possible to assign sex from measurements taken on certain elements as size can also be an indicator of sex (Bass 1995; Chamberlain 1994). Sex has been assigned as male or female when the features present are certain, or probable male and probable female where sex is probable but not entirely certain. The definite and probable male and female categories will be pooled for the analysis. For some very partial individuals sex will have been unable to have been assigned and these will be recorded as undetermined. None of the sub-adult individuals have been assigned sex as the techniques being developed need to be tested on other collections of sub-adults of known sex before they can be used with confidence on archaeological material (Mays 2007, 92). Metrical data was recorded for the crania and postcrania according to Buikstra & Ubelaker (1994) and Brothwell (1981). Cranial non-metrics were scored as Berry & Berry (1967) and Hauser & De Stefano (1989) and postcranial non-metrics were scored as Finnegan (1978). Stature estimation was calculated using the prediction equations of Trotter & Glesser as cited in Brothwell & Zakrzewski (2004, 33). These equations should be used with caution however as they were devised using American samples. 7 Methods [Songo Mnara 2011]

8 For the determination of ethnic ancestry, the complete crania were initially assessed visually (anthroposcopically). The general craniofacial traits denoting an individual of African ancestry includes a wide nasal aperture, nasal guttering, marked alveolar prognathism, wide intraorbital distance, a long, low cranial shape with a postbregmatic depression (Krogmanand Işcan, 1986: 271; Ubelaker, 1999, 119; White and Folkens, 2005: 404). For complete skulls it is possible to make a complementary assessment of ethnic ancestry by comparing standard measurements between populations of known provenance in order to assess degrees of similarity and difference using linear discriminant analysis and nearest neighbour discriminant analysis (anthropometric analysis). These analyses were undertaken using Cranid 6 (Wright 2007), which takes account of 29 standard measurements on an individual cranium. It assumes that the individual cranium is within the range of variation of modern Homo sapiens. The cranium is classified after comparison with 74 samples numbering 3,163 crania from around the world, including populations from East, West, and South Africa, Europe, Egypt and India. Each bone was analysed for any evidence of abnormality and comparisons were made to the literature on palaeopathology. The standard texts referred to were Ortner (2003), Waldron (2009), Aufderheide & Rodriguez-Martin (1998), and Roberts & Manchester (1995). Vertebral osteoarthritis and osteophytosis were scored on a scale of 0-3 (Brothwell 1981). Cribra orbitalia and porotic hyperostosis were scored as Stuart-Macadam (1991). Dental calculus and periodontal disease were scored as Brothwell (1981). Results Information for each individual adult skeleton on preservation, age, sex, stature, dental presence and dental health are listed in Appendix 1. Details of skeletal pathology on the adult skeletons are listed in Appendix 2. Information on 8 Results [Songo Mnara 2011]

9 preservation, age, and dental presence for the sub-adult skeletons is listed in Appendix 3. Preservation The preservation of the skeletal remains across the site was generally good. 50% percent of the skeletons were described as being in an excellent or good state, 28% as fair and only 22% as poor. Root markings were present on some skeletons but mostly to a small degree. Erosion and fragmentation of the ribcage and vertebrae was fairly common and fragmentation of the skulls was noted in some cases. Surface erosion tended to be fairly slight with most of the skeletons only falling into the grade 1 or 2 categories. 83% of the juvenile skeletons were found to be in a poor or fair state, as compared with only 25% of the adults. 50% of the skeletons were over 75% complete, 20% were represented by close to half of the expected skeletal elements, and only 30% were represented by less than a quarter of the skeletal elements. 66% of the juvenile individuals were at least 50% complete, as compared with 75% of the adults. Demography Of the fourteen sets of remains exhumed, twelve were articulated skeletons. Of these twelve, six were adult, and six sub-adult. Of the six adults five were classed as definite males and one as a definite female. Table 1 shows the number of sub-adult skeletons present by age group and Table 2 shows the number of adult skeletons present by age group and by sex. Table 1: Sub-adult ages. Age at death (years) number of individuals preterm/neonate 2 9 Results [Songo Mnara 2011]

10 60 days up to 0.5yrs up to 2yrs 3 2 up to 6yrs 0 6 up to 10yrs 1 10 up to 15yrs 0 15 up to 20yrs 0 Total 6 Table 2: Adult age and sex. Age Category males females unidentified Total Young adult Middle adult Old adult Adult 2 2 Total The ratio of sub-adults to adults represented in this collection is roughly 1:1 but as can be seen in Table 2 the ratio of males to females appears high at 5:1. Further research is required to establish whether this pattern is normal for east African, or indeed Islamic, burial sites of this period. It may be, for example, that male and female burials may be separated across the site. A caveat to this, however, lies in the tendency for some osteological techniques to identify more males than females (Mays & Cox 2000, 125) and this may be another contributing factor. The four trenches (24, 25, 26 and 27) appear to have subtly different demographic profiles; for example, the young female skeleton was found in the same context as two sets of child remains, whereas trench 24 contained three adults. 10 Results [Songo Mnara 2011]

11 Ethnic ancestry Five adult skulls were complete enough to be assessed anthroposcopically and anthropometrically for ethnic ancestry. These were SK3, 8 and 13 (middle-aged males), 4 (young male), and 9 (young female). The primary aim of this analysis was to indicate whether the individuals present in the Songo Mnara cemetery are most likely to be of African, Middle Eastern, or European biological ancestry. SK3: Anthroposcopic assessment African. Linear discriminant analysis results: Order Sample Probability 1 Teita_E._Afr_M Zulu_S._Afr_F Of the population samples included in the Cranid 6 database, this skull matches with the highest probability with a sub-saharan African population. There is a high probability that SK3 is of African ancestry. Nearest neighbour discriminant analysis results: Actual nearest neighbour: Teita_E._Afr_M Sample number Sample name Hits Weighted score 4 Teita_E._Afr_M Teita_E._Afr_F Dogon_W._Afr_F Zulu_S._Afr_F Results [Songo Mnara 2011]

12 Distance of individual from its nearest neighbour Distance of individual from the centroid Of the population samples included in the Cranid 6 database, the nearest neighbour to this skull is a sub-saharan African. However, the statistical distance between SK 3 and the nearest neighbour is , which is far from the mean value of for the MNND of the Cranid 6 database. This means that there is no very close match for the skull within the database. SK4 Anthroposcopic assessment African. Linear discriminant analysis results: Order Sample Probability 1 Dogon_W._Afr_M Dogon_W._Afr_F Of the population samples included in the Cranid 6 database, this skull matches with the highest probability with a West African population. There is a high probability that SK4 is of African ancestry. Nearest neighbour discriminant analysis results: Sample number Sample name Hits Weighted score 5 Dogon_W._Afr_M Dogon_W._Afr_F India_F Andaman_Is._F Results [Songo Mnara 2011]

13 Distance of individual from its nearest neighbour Distance of individual from the centroid Of the population samples included in the Cranid 6 database, the nearest neighbour to this skull is a West African. However, the statistical distance between SK 4 and the nearest neighbour is , which is greater than the mean value of for the MNND of the Cranid 6 database. This means that there is no very close match for the skull within the database. SK8: Anthroposcopic assessment African with a possibility of mixed ethnicity. Linear discriminant analysis results: Order Sample Probability 1 Easter_I._F Easter_I._M Sydney_F Sydney_M Italian_M Mokapu_Hawaii_F Of the population samples included in the Cranid 6 database, this skull matches with the highest probability with an Easter Island population, followed by an indigenous Australian population. There is a possibility that this individual is of mixed ancestry, and/or there is no good population match within the Cranid 6 database. 13 Results [Songo Mnara 2011]

14 Nearest neighbour discriminant analysis results: Sample number Sample name Hits Weighted score 40 Easter_I._F Easter_I._M Sydney_M Sydney_F Distance of individual from its nearest neighbour Distance of individual from the centroid Of the population samples included in the Cranid 6 database, the nearest neighbour to this skull is an Easter Islander. However, the statistical distance between SK 8 and the nearest neighbour is , which is greater than the mean value of for the MNND of the Cranid 6 database. This means that there is no very close match for the skull within the database. SK9: Anthroposcopic assessment African with a possibility of mixed ethnicity. Linear discriminant analysis results: Order Sample Probability 1 Sydney_F Tolai_New_Britain_F Tolai_New_Britain_M Easter_I._F Results [Songo Mnara 2011]

15 5 Moriori_Chat_Is_F Tasmania_F Patagonian_F Zulu_S._Afr_F Of the population samples included in the Cranid 6 database, this skull matches with the highest probability with an Australian population. There is a possibility that this individual is of mixed ancestry, and/or there is no good population match within the Cranid 6 database. Nearest neighbour discriminant analysis results: Actual nearest neighbour: Punjab_F Sample number Sample name Hits Weighted score 38 Tolai_New_Britain_F Sydney_M Punjab_M Sydney_F Easter_I._M Arikara_Dakota_F Tasmania_F Zulu_S._Afr_F Distance of individual from its nearest neighbour Results [Songo Mnara 2011]

16 Distance of individual from the centroid Of the population samples included in the Cranid 6 database, the nearest neighbour to this skull is from New Britain. However, the statistical distance between SK 9 and the nearest neighbour is , which is greater than the mean value of for the MNND of the Cranid 6 database. This means that there is no very close match for the skull within the database. SK13: Anthroposcopic assessment African. Linear discriminant analysis results: Order Sample Probability 1 Teita_E._Afr_M Teita_E._Afr_F Dogon_W._Afr_M Easter_I._F Easter_I._M Zulu_S._Afr_M Of the population samples included in the Cranid 6 database, this skull matches with the highest probability with a sub-saharan African population. There is a high probability that SK13 is of African ancestry. 16 Results [Songo Mnara 2011]

17 Nearest neighbour discriminant analysis results: Actual nearest neighbour: Dogon_W._Afr_M Sample number Sample name Hits Weighted score 4 Teita_E._Afr_M Dogon_W._Afr_F Zulu_S._Afr_M Zulu_S._Afr_F Dogon_W._Afr_M Mokapu_Hawaii_F Distance of individual from its nearest neighbour Distance of individual from the centroid Of the population samples included in the Cranid 6 database, the nearest neighbour to this skull is from sub-saharan Africa. However, the statistical distance between SK 13 and the nearest neighbour is , which is greater than the mean value of for the MNND of the Cranid 6 database. This means that there is no very close match for the skull within the database. 17 Results [Songo Mnara 2011]

18 Metrics and non-metrics Metrics The mean estimated statures for males are shown in Table 3 (the female skeleton was not complete enough to include). These data describe a male population of modest average stature compared to European populations of a similar period where the mean male stature is 171cm (Roberts & Cox 2003, 248). Table 3: Estimated stature of the adults N Mean estimated stature Range Standard deviation Male 4 151cm cm 5.00 Female Non-metrics Those few non-metric traits which had at least one trait present within the population are shown below in Table 4 for the cranial traits. No non-metric postcranial traits were observed. Scores for right and left sides have been recorded separately (L for left and R for right) while those traits which fall on the midline are indicated by M. The % present column shows the percentage of individuals scored which have this trait. Nine crania were able to be scored for some or all cranial traits and twelve skeletons for some or all postcranial traits. Table 4: Cranial non-metric traits present. Non-metric cranial trait Present Absent % Present L M R L M R L M R lambdoid ossicle % 29% apical bone % 18 Results [Songo Mnara 2011]

19 L = left, R= right, M = midline These two traits of the cranium observed have a fairly high incidence; they involve the apical bone (an extra bone at the back of the skull where the occipital and parietal bones meet) and the presence of lambdoid ossicles (extra bones at the back of the skull along the lambdoid sutures). There are no immediately obvious clusters of traits within the cemetery which may have suggested locations where members of the same family were buried. The Dentition Dental health The following Tables 5-8 show the incidence of ante-mortem tooth loss (AM loss), caries, enamel hypoplasia (EH), abscess presence, and periodontal disease by individual skeletons and teeth scored. Incidences are recorded by age and sex for adults. Four sub-adult dentitions were available for study, but none demonstrated any enamel hypoplasia or caries. One (SK 3) presented a tooth broken in life (right 2 nd left premolar). In general it appears that across the adult population basic dental anatomy is good (no enamel hypoplasia) but dental health is relatively poor. All the dentitions present periodontal disease and some degree of calculus build-up, and half of the middle aged males experienced ante-mortem tooth loss. Table 5 Dentitions, ante-mortem tooth loss and caries present by age and sex. Dentitions AM loss %loss Caries %caries Y males Y females M males Results [Songo Mnara 2011]

20 Table 6: Enamel hypoplasia, abscess and periodontal disease presence. EH %EH Abscess %abscess Periodontal %periodontal Y males Y females M males Table 7: Caries and enamel hypoplasia presence by teeth scored. Caries Teeth scored %teeth EH Teeth scored %teeth Y males Y females M males Table 8: Calculus presence by teeth scored. Total teeth Calculus %teeth Y males Y females M males Results [Songo Mnara 2011]

21 Figure 1: Abscess and periodontal disease in a young male (SK3). Congenital anomalies No congenital anomalies were observed in any of the dentitions. Congenital absence of the third molar, or non-eruption caused by impaction, can have a relatively high frequency in some populations (Schwartz 1995, 167). It is unusual for a population not to express these traits at all. Palaeopathology Various pathologies have been recorded on the individual skeletons and these are all listed in the Appendix. This section will refer to some incidences for the more common types of pathology recorded and some individuals with specific cases will be described. Five sub-headings have been included in this section: infectious disease; degenerative joint disease; metabolic disease; neoplastic disease; and congenital anomalies. 21 Results [Songo Mnara 2011]

22 Infectious Disease Infectious disease would have been the greatest cause of death during the late medieval period. Infection, whether of soft tissue or bone, is associated with the pathological process of inflammation as a reaction to the invading organism (Roberts & Manchester 1995, 125). Most bone lesions caused by infection seen on archaeological remains are termed non-specific infection. This is because the processes of the bacteria involved, such as staphylococci or streptococci, on bone are indistinguishable from each other. Some infectious diseases do have more diagnostic lesions; tuberculosis is the only type where any evidence is seen for specific infectious disease in this population. Infectious disease would have been a major cause of death in the late medieval period across the world, however there is not a great deal of evidence for infection that can be seen among this population. This is because it is likely that most individuals would have died from infectious disease before involvement of the bones took place. The single incidence of non-specific infection (periostitis) is observed in SK 4 on the ribs. Periostitis occurs when the periosteum which surrounds the living bone becomes irritated by infection or trauma to the area and produces new bone. This originates as disorganised and porous (woven) bone in the active stage and later becomes smooth and organised (lamellar) bone as healing takes place. In sub-adults it is possible that the occurrence of patches of woven bone across the skeleton may be a product of the normal growth process so care needs to taken when diagnosing the cause to be of infectious origin (Lewis 2007, 135). Presence on the ribs is probably due to the fact that this region is not well protected by soft tissue and is often prone to slight trauma. 22 Results [Songo Mnara 2011]

23 Degenerative joint disease Osteoarthritis Osteoarthritis (OA) is a common finding among the older individuals in skeletal populations across the world. It is a disease of the joints, involving the breakdown of the articular cartilage, and can be caused due to the degenerative changes associated with the wear and tear of old age (and possibly physical occupation). It can also be secondary due to trauma causing later problems within the associated joint. Initially the changes to the joint involve new bone formation around the margin of the joint termed marginal osteophytes (MOP), later the joint surface can become pitted and porous and the normal contour of the joint widened or flattened. In severe cases eburnation will be present. Eburnation is when the surface of the bone becomes highly polished and smooth, sometimes containing grooves showing the direction of movement of the joint. This polishing occurs due to the constant rubbing of the two articular surfaces or due to the presence of debris within the joint (Waldron 2009, 28). In clinical patients the area surrounding the joint will show swelling and be painful, the joint space is also seen to narrow on radiographs. Osteoarthritis is diagnosed only when either eburnation is present or both MOP and porosity (Waldron 2009, 34). Table 9: Osteoarthritis by side in the appendicular skeleton. Joint Right Left Unsided Shoulder Marginal osteophytes can be a product of general ageing and therefore cannot be used alone to diagnose OA. Table 9 shows that the incidence of osteoarthritis across the appendicular skeleton was rare in this population; eburnation and/or both MOP and porosity occurred only in one region on one skeleton. The unilateral nature of 23 Results [Songo Mnara 2011]

24 this pathology is possibly related to right handedness and therefore more usage of the right side of the body (Figure 2 and 3). Figure 2: Osteoarthritis in the right shoulder; osteophyte formation and pitting in the right clavicle (SK 3) Figure 3: Osteoarthritis in the right shoulder; osteophyte formation and pitting in the glenoid fossa (SK 3). 24 Results [Songo Mnara 2011]

25 Four individuals have OA of one or more joints across the skeleton, some at one joint only and others at up to several different joints/areas of the body. Table 10 shows the incidence of osteoarthritis for each joint by age and sex. Osteoarthritis can also be scored on the superior and inferior articular surfaces of the vertebrae; these have been scored as Brothwell (1981). Osteoarthritis of the articulations is recorded as present if the scores are of grade 2 or above. The presence of osteophytosis and intervertebral disc disease has also been scored as Brothwell (1981). Degeneration of the vertebral disc can lead to osteophytes (bony bridges) forming to support the vertebrae as the soft tissue of the disc bulges outwards (grade 1). Pitting and porosity of the body of the vertebrae can also occur as the disc degenerates further (grade 2-3). These changes can be associated with ageing, and/or in response to activity related trauma such as might be caused by extreme torsion or compressive loading of the spine. In this population, OA and IVDD is observed across the whole spine. All four of the individuals affected are males. It is possible that these degenerative changes can lead to fusion of the vertebrae and this appears to be the case in the lumbar spine of one example (SK8). Table 10: Skeletons with osteoarthritis. SK age/sex Shoulder Cervical spine Thoracic spine Lumbar spine 3 M/M 4 Y/M 8 M/M 13 M/M M/M = middle-aged adult male, Y/M = young adult male 25 Results [Songo Mnara 2011]

26 Figure 4: Osteoarthritis in the spine with Schmorls nodes (SK 4). Figure 5: Fusion in the lumbar spine (SK 8) 26 Results [Songo Mnara 2011]

27 Metabolic disease Cribra orbitalia Cribra orbitalia manifests as porosity within the orbits of the skull (Figure 6), and this is normally understood as the bone marrow expanding for increased red blood cell production. Cribra has long been linked with iron deficiency anaemia (Mensforth et al. 1978; Larsen 1997) and in women and children rates tend to be higher due to the need for more iron in growing children and childbearing women and due to the loss of iron during menstruation. However the link to iron deficiency anaemia has been questioned more recently (Waldron 2009, 137) and this condition may have a closer link to infectious disease or parasitism affecting how the body stores and distributes iron rather than to a dietary deficiency (Lewis 2007, 113; Stuart-Macadam 1991). Table 11: Incidence of cribra orbitalia. Grade 0 Grade 1 Grade 2 Grade 3 Grade 4 males females Total Results [Songo Mnara 2011]

28 Figure 6: Cribra orbitalia in the right orbit (SK 9). Neoplastic disease Osteomas consist of overgrowths of normal bone that are formed within the periosteum; they are common finds in skeletal remains and are benign growths (Waldron 2009, 171). One male (SK 3) has a small button osteoma present on the skull, located on the frontal bone. Congenital anomalies Axial skeleton Two cases, both in middle-aged males, of partial non-union of the constituent bones of the sacrum were recorded. SK 4 presents partial non-union of the sacral S1-S2 joint. This is a relatively common variant, with no documented implications for function. SK 13 presents more severe non-union of the neural arch of the sacral vertebrae S1-S5. This is a form of spina bifida occulta, but is very unlikely to have caused debilitating symptoms in the living person because the upper spine is not affected. 28 Results [Songo Mnara 2011]

29 Figure 7: Spina bifida in the sacrum of SK 13. Discussion The purpose of this pilot osteoarchaeological study was to evaluate: a) The state of preservation of human remains across the cemetery areas. Results have shown that the preservation is good across the site. There is every possibility that further excavation would reveal a large number of well preserved sets of remains representing all age groups and both sexes. b) The relationship between funerary architecture and burial characteristics. Results have shown that the four trenches (24, 25, 26 and 27) excavated during this season appear to have subtly different demographic profiles; for 29 Discussion [Songo Mnara 2011]

30 example, the young female skeleton was found in the same context as two sets of child remains, whereas trench 24 contained three adults. There is an intriguing relationship between sub-adult and adult inhumations, with the latter lying underneath the former. These findings require further investigation. c) Where appropriate, the age, sex, ethnicity and health status of the exhumed remains. Results show a preliminary ration of adult males to females of 5:1. This generates all kinds of questions as to the differential burial of males and females within the site. This pilot study has also shown that average age at death was relatively low compared at least to contemporary European populations; we need to explore whether this actually is the case, rather than being a function of small sample size. Finally the ethnicity assessment has suggested that the population is indeed African, although further comparison with other populations is required. d) The potential of the site for further excavation and osteoarchaeological investigation. These pilot results have indicated a population under stress. Short stature, poor dental health, spinal osteoarthritis in nearly all adult males, low average age at death, and a high proportion of sub-adult burials are all interesting findings we need to explore in more detail. References Cited Aufderheide, A. C. and Rodriguez-Martin, C. (1998) The Cambridge Encyclopedia of Human Paleopathology, Cambridge University Press. Barnes, E and Ortner, D. J. (1997) Multifocal eosinophilic granuloma with a possible trepanation in a 14th century Greek young skeleton, International Journal of Osteoarchaeology 7: References Cited [Songo Mnara 2011]

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