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Feb082014

Nutritional values of tortoises relative to ungulates from the Middle Stone Age levels at Blombos Cave, South Africa: Implications for foraging and social behaviour

Thompson, J. & Henshilwood, C.S. 2014. Nutritional values of Middle Stone Age tortoises at Blombos Cave, South Africa, and implications for foraging and social behaviour. Journal of Human Evolution 67: 33–47. 

The site of Blombos Cave (BBC), Western Cape, South Africa has been a strong contributor to establishing the antiquity of important aspects of modern human behaviour, such as early symbolism and
technological complexity. However, many linkages between Middle Stone Age (MSA) behaviour and
the subsistence record remain to be investigated. Understanding the contribution of small fauna such
as tortoises to the human diet is necessary for identifying shifts in overall foraging strategies as well as
the collecting and processing behaviour of individuals unable to participate in large-game hunting.
This study uses published data to estimate the number of calories present in tortoises as well as
ungulates of different body size classes common at South African sites. A single tortoise (Chersina
angulata) provides approximately 3332 kJ (796 kcal) of calories in its edible tissues, which is between
20 and 30% of the daily energetic requirements for an active adult (estimated between 9360 kJ
[3327 kcal] and 14,580 kJ [3485 kcal] per day). Because they are easy to process, this would have made
tortoises a highly-ranked resource, but their slow growth and reproduction makes them susceptible to
over-exploitation. Zooarchaeological abundance data show that during the ca. 75 ka (thousands of
years) upper Still Bay M1 phase at BBC, tortoises contributed twice as many calories to the diet relative
to ungulates than they did during the ca. 100 ka lower M3 phase. However, in spite of the abundance of
their fossils, their absolute caloric contribution relative to ungulates remained modest in both phases.
At the end of the site’s MSA occupation history, human subsistence strategies shifted to emphasise
high-return large hunted mammals


Selected Images

Human modification on tortoise elements with enlargements of areas of interest at right: a) two cut marks on a limb; b) a scrape mark on the interior of the carapace, with the boundaries indicated by arrows; c) and d) percussion marks on the exterior of the carapace with arrows indicating microstriation patches within smoothed areas where the bone surface has been compressed and the texture modified by contact with the percussor.


 

The distribution and intensity of burning patterns on the shell showing preferential burning on the carapace and around the edges of the plastron, and indicating cooking carapace side down while the tortoise was complete. Darker areas are more heavily burned parts of the skeleton and white hollow areas are places in the skeleton not represented by any specimens.



URL Link

 

http://www.sciencedirect.com/science/article/pii/S0047248413002431






 

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