Femoral cortical thickness of North American Plains Indians • 107 



trast, marked sample differences are 

 present in the amounts of cortical bone, 

 as measured by the variables C. Nl and 

 CA. The separate patterns reflected by 

 male and female measurements reveal 

 marked correspondence. Mean values 

 for C and Nl for the Early Protohistoric 

 period represent the high peaks for this 

 time series. Cortical thickness in- 

 creased in both sexes during the transi- 

 tion from the Late Prehistoric to the 

 Early Protohistoric period. These 

 gains, however, were only temporary 

 and not sustained in the more recent 

 time periods. Later samples have re- 

 duced cortical thicknesses. Both sexes 

 correspond in this trend, although 

 females reveal the most dramatic loss of 

 tubular bone. 



Sample differences in C and Nl re- 

 flect net changes in both the medullary 

 cavity diameter and the total sub- 

 periosteal diameter. In females, me- 

 dullary widths decreased during the 

 Early Protohistoric period. Late Pro- 

 tohistoric and Historic period female 

 values returned to the Late Prehistoric 

 average diameter and then greatly sur- 

 passed this base, more closely approx- 

 imating the larger diameters of males. 

 Males during the Late Protohistoric and 

 Historic periods are characterized by 

 larger medullary cavity diameters than 

 found decades earlier in Arikara popu- 

 lations. Total subperiosteal diameters 

 also show temporal change with mean 

 values for T increasing through time, 

 especially in males. In terms of estimat- 

 ed cortical areas, these small increases 

 in T diminish the effect of the linear 

 increases in M, the smaller diameter. In 

 both sexes, calculated cortical areas 

 show the largest increase with the tran- 

 sition from the Late Prehistoric to the 

 Early Protohistoric period. Because of 

 the increase in T, cortical areas con- 

 tinue to increase through the Late Pro- 

 tohistoric period, followed by decline 

 during the early Historic period. In the 

 most recent period, male and female 

 cortical areas, although approaching 

 the early 17th century base line (espe- 

 cially in females) are still higher than 

 during the Late Prehistoric Period. 



1500- - 



I4O0-. 



liOO-. 



1200.. 

 mm 



FEMALES 

 •MALES 



LATE 

 PREHISTORIC 



EARLY 

 PROTOHISTORIC 



LATE 

 PRerOHISTORIC 



HISTORIC 



Figure I . Femur midshaft cortical thickness by time period 



0.57 . 



0.56 



055 .. 



Q54 .. 



0.53 .. 



0.52 . 



Oil .. 



050 ■■ 



0.49 .. 



0.48 



0.47 



Nl 



FEMALES 



MALES 



-I- 



LATE 

 PREHISTORIC 



EARLY 

 PROTOHISTORIC 



LATE 

 PROTOHISTORIC 



HISTORIC 



Figure 2. Temporal variation in Nordin's Index 



Zagreb Paleopathology Symp. 1988 



