A morphometric investigation into shrunken heads

This is a first time morphometric investigation into 65 shrunken heads from South America, comprising 6 ceremonial tsantsa, 36 commercial heads, and 23 ambiguous heads. Ceremonial tsantsa are heads ritually reduced by the Shuar, Achuar, Awajún (Aguaruna), Wampís (Huambisa) and Candoshi-Shapra, following a long-standing war trophy tradition. Commercial heads were produced solely for trade since c.1872. Ambiguous classified heads resemble ceremonial tsantsa, but demonstrate minor questionable anomalies in their design. Thirty-two dimensions were reliably collected utilizing a sliding caliper, soft measuring tape and multi-detection computerized tomography (MDCT). Box and whisker charts plot the range in dimensions identified for each shrunken head category, including collection total. Ceremonial tsantsa were most consistent in scale. Sample sizes were small, but the long-established and religious nature of applied techniques likely influenced this result. Ambiguous heads were closely affined, but wider ranging in scale to ceremonial tsantsa. Commercial heads, produced using irregular methods, demonstrated the strongest variation in scale. They were generally larger, but presented both the very largest and smallest heads in the collection. The largest heads (with c.7-8 mm visible tissue depth) were marked with mould, suggesting improper processing and desiccation; hair analysis confirmed the smallest (c.1.2-1.7 mm visible tissue depth) were of juveniles. Visible tissue depths, taken from skin lining the neck/head opening, was typically c.3-4 mm. MDCT analysis otherwise identified a tissue depth variance of 1.95-3.67 mm minimum (common in upper face and inferior to chin regions) and 3.49-10.09 mm maximum (at vertex). Ceremonial and ambiguous heads often presented moderately thicker, heavier skins to commercial heads, with evident papillary and reticular layer separation of the dermis, from an imbalanced heat application and pronounced manual manipulation during desiccation. To advance research findings, a greater sample size of ceremonial tsantsa is required to ideally identify morphometric parameters that definitively differentiate ceremonial and commercial heads.