Reconstructing Mobility and Workload in Guale Populations from the Georgia Coast

C. Kinley Russell1, Christopher B. Ruff1, & Clark Spencer Larsen2

1Center for Functional Anatomy & Evolution, Johns Hopkins University School of Medicine,2Department of Anthropology, The Ohio State University

IntroductionFrom the prehistoric period through the 18th century, Guale people adapted to new subsistence strategies involving intensive maize farming and Spanish missionization in a number of ways.1,2,3

The Fallen Tree site provides new evidence of a protohistoric pre-mission population who lived on St. Catherines Island, Georgia. Long bone cross-sectional properties have been shown to vary in response to mechanical loading in experimental settings and in past populations.1,2,3 Here we apply this approach to reconstruct changing patterns of behavior in prehistoric and early historic Gualepopulations from the Georgia Coast.

Humeral strength declines through the early Mission period and then increases at Amelia Island Mission, especially in males.This may be related to general reductions in upper limb loading through time, but an increase in lifting activities at Amelia Island Mission. Standardized humeral mid-distal average bending rigidity (J Std) for Fallen Tree is intermediate between Prehistoric Maize Agricultural and St. Catherines Mission samples, and significantly lower than for Amelia Island Mission (p<0.05). This suggests that the increased workload on the upper limb inferred for the Amelia Island Mission sample was unlikely in the Fallen Tree population.

References1. Ruff CB & Larsen CS, 2001. Reconstructing behavior in Spanish Florida. In: Bioarchaeology of Spanish Florida:

The Impact of Colonialism, ed. CS Larsen. University of Florida Press, Gainesville, pp. 113-145.2. Ruff CB, 2008. Biomechanical analyses of archaeological human skeletons. In: Biological Anthropology of the

Human Skeleton, 2nd edn, eds. MA Katzenburg & SR Saunders. John Wiley & Sons, New York, pp. 183-206.3. Ruff CB & Larsen CS, 2014. Long bone structural analyses and the reconstruction of past mobility: a historical

review. In: Reconstructing Mobility: Environmental, Behavioral, and Morphological Determinants, eds. KJ Carlson & D Marchi. Springer Science+Business Media, New York, pp. 13-29.

4. Ruff CB, (n.d.). MomentMacro: http://www.hopkinsmedicine.org/fae/mmacro.htm.5. Ruff CB, 2018. Quantifying skeletal robusticity. In: Skeletal Variation and Adaptation in Europeans: Upper

Paleolithic to the Twentieth Century, ed. CB Ruff. John Wiley & Sons, New York, pp. 39-47.

Fig. 5. Box plots of H35 J Std, pooled and by sex..

Population Time Range Male Female ? TotalPrehistoric Pre-Maize

McLeod Mound, Deptford Site, Airport, Cannons

Point, Sea Island Mound, Charlie King Mound

Pre-1150 10 10 20

Prehistoric Maize Agricultural

Johns Mound, Marys Mound, Irene, Martinez B,

Taylor Mound, Couper Field

1150-1550 28 32 60

Fallen Tree

Fallen Tree Cemetery

1500-1550 13 16 7 36

St. Catherines Mission

Pine Harbor, Santa Catalina de Guale

1607-1680 9 9 18

Amelia Island Mission

Santa Catalina de Santa Maria

1686-1702 24 23 47

Total 84 90 7 181

Materials and methodsPeripheral quantitative CT scans of 36 adult individuals from the Fallen Tree site were taken at the femoral midshaft, femoral subtrochanteric, and humeral mid-distal regions. Section locations were determined from bone length’1 and images with matrix infill or missing cortex were digitally repaired. Properties were determined using the MomentMacro plug-in for ImageJ and standardized by dividing by body size (body mass*bone length2).4,5 Data were then compared for prehistoric pre-maize, prehistoric maize agricultural, pre-mission contact era, early mission, and late mission samples. All contact era populations sampled are maize farmers.

Sample

Results

There is a significant increase in static loading of the femur in Guale populations over time, consistent with a decrease in mobility and increase in burden carrying.Femoral subtrochanteric maximum to minimum bending rigidity (Imax/Imin) declines over time, which may be related to increases in static loading of the lower limb (from reductions in mobility and increases in weight support, e.g., from carrying burdens). Fallen Tree males have significantly greater standardized maximum bending rigidity than Amelia Island Mission males (Imax Std, p=0.04) and greater standardized maximum and minimum bending rigidities than Prehistoric Maize-farming males (Imax Std, p<0.05; Imin Std, p<0.001).

Sex-Specific Femoral Subtrochanteric Minimum Bending Rigidity, Standardized by Body Size

Pooled Femoral Subtrochanteric Maximum/Minimum Bending Rigidity

The Fallen Tree population does not show the same declines in mobility seen in later mission populations. Fallen Tree males (like Pre-Maize males) were significantly more mobile than Maize Agricultural males.The ratio of A-P to M-L bending rigidity (Ix/Iy) at the femoral midshaft is significantly higher in the Fallen Tree and Pre-Maize populations than in the Amelia Island Mission population (p=0.03). Males in both the Fallen Tree and Pre-Maize populations have significantly higher standardized femoral midshaft A-P bending rigidity than males in the Maize Agricultural group (Ix Std, p=0.02).

Sex-Specific Femoral Midshaft A-P Bending Rigidity, Standardized by Body Size

Pooled Femoral Midshaft A-P/M-L Bending Rigidity

Percent cortical area generally declines over time, indicating a possible decrease in general health status beginning with Fallen Tree. However, this result should be considered in combination with other paleopathological indicators.

Sex-Specific Humeral Mid-Distal Average Bending Rigidity, Standardized by Body Size

Pooled Humeral Mid-Distal Average Bending Rigidity,Standardized by Body Size

Pooled Humeral Mid-Distal Percent Cortical Area

There is a general, though non-significant, temporal decline in mid-distal humeral percent cortical area (%CA) between the prehistoric populations and the Fallen Tree and mission populations. For this analysis, samples were limited to adults under age 40 to limit the confounding effects of age-related changes to cortical area.

AcknowledgementsThis research was supported by the St. Catherines Island Foundation, the National Science Foundation, The Ohio State University, and Johns Hopkins University School of Medicine. We would like to thank the St. Catherines Island archaeological team for their work in the excavation, cataloguing, and loan of the individuals analyzed in this study. We would also like to thank the participants of the Caldwell IX St. Catherines Island Workshop (made possible by the AMNH) for their feedback and continued collaboration.

Femoral Subtrochanteric(80% of length’)

Imax: Maximum second moment of area

Imin: Minimum second moment of area Iy

Ix

Iy

Ix

Imin

Imax

J = Ix + Iy

%CA=(CA /TA)*100

Prehistoric Prehistoric Fallen St. Catherines AmeliaPre-Maize Maize Tree Mission Mission

Prehistoric Prehistoric Fallen St. Catherines AmeliaPre-Maize Maize Tree Mission Mission

Prehistoric Prehistoric Fallen St. Catherines AmeliaPre-Maize Maize Tree Mission Mission

Prehistoric Prehistoric Fallen St. Catherines AmeliaPre-Maize Maize Tree Mission Mission

Prehistoric Prehistoric Fallen St. Catherines AmeliaPre-Maize Maize Tree Mission Mission

Prehistoric Prehistoric Fallen St. Catherines AmeliaPre-Maize Maize Tree Mission Mission

Prehistoric Prehistoric Fallen St. Catherines AmeliaPre-Maize Maize Tree Mission Mission

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J: Polar secondmoment of area

CA: Cortical areaTA: Total subperiosteal

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Ix: Second moment of area about x-axis

Iy: Second moment ofarea about y-axis