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Ancestry differences and secular trends in the anthropometric lower limb proportions of South African black and white females
Ancestry differences in lower limb proportions
The mean crural index ([leg length/thigh length] x100), total lower limb ratio (total lower limb length/stature), lower limb ratio (lower limb length/stature), thigh ratio (thigh length/stature) and leg ratio (leg length/stature) of both SABF and SAWF are shown in Table 5.6. The non-parametric Kruskal-Wallis test, which is equivalent to the parametric analysis of variance for the lower limb proportions, classified by ancestry using the SAS NPAR1WAY procedure, was used to determine whether significant differences exist between SABF and SAWF.
Over the combined birth cohort, a significant difference was observed in the total lower limb length, lower limb length, leg length and lateral femoral epicondyle length with SAWF having overall larger lower limb measurements than SABF (Appendix B2; Table B2.2 and Figures B2.3 and B2.4). However, no significant difference was observed in the thigh length (0.0805). In Table 5.6 the difference in the lower limb proportions between SABF and SAWF for all birth cohorts combined can be seen. All lower limb proportions were significantly different between SABF and SAWF (p < 0.0001). SABF had total lower limb ratios, lower limb ratios, thigh ratios and leg ratios which were higher than those of SAWF.
This indicates that SABF have greater total lower limb lengths, lower limb lengths, proximal lengths and leg lengths relative to stature than SAWF. A higher crural index was observed in SAWF compared to SABF which indicates greater leg lengths relative to thigh lengths in SAWF.
Table 5.6 and Figure 5.21 demonstrate that in the 1940’s to 1970’s no significant difference was observed in the crural index between SABF and SAWF (p > 0.005). This indicates slightly shorter leg lengths relative to thigh lengths up to the 1970’s after which the leg lengths became significantly greater relative to thigh lengths in SAWF. No significant difference was observed in the 1940’s and 1950’s for the total lower limb ratio and no significant differences was observed in the thigh ratio from the 1940’s to 1960’ with slightly higher values still observed in SABF. The differences in the thigh ratio only changed significantly after the 1960’s. The leg ratio exhibited no significant differences in the 1940’s, 1950’s and 1980’s. During the 1980’s, SAWF had leg ratios which were slightly higher than those of SABF indicating slightly greater leg lengths relative to stature.
Secular trends in lower limb proportions
Comparison of the crural index, total lower limb ratio, lower limb ratio, thigh ratio and leg ratio plotted against Date of Birth (DOB) cohorts of 10 years using the SAS NPAR1WAY procedure for SABF and SAWF indicated both positive and negative secular trends in the lower limb proportions from 1941 to 1990. Overall the crural index showed significant negative secular trends in both SABF (Kruskal-Wallis Chi-squared = 214.6804; p < 0.0001) and SAWF (Kruskal-Wallis Chisquared = 14.8246; p = 0.0051) indicating a decrease in the leg lengths relative to the thigh lengths in both groups. Figure 5.22 demonstrates that the crural index in SABF initially increased from 107.80 in the 1940’s to 110.94 in the 1960’s followed by a decrease to 93.64 in the 1990’s while the crural index of SAWF decreased from 114.64 in the 1940’s to 103.56 in the 1980’s. This indicates that during the 1940’s to 1960’s, the crural index of SABF were becoming more similar to those of SAWF until the 1970’s (SABF index: 108.82; SAWF index: 108.68) when SABF had slightly greater leg lengths relative to thigh lengths.
However, the leg lengths relative to thigh lengths became significantly less after the 1970’s in SABF.
A significant positive secular trend is observed in the total lower limb ratio for SABF (Kruskal-Wallis Chi-squared = 28.9985; p < 0.0001) with no significant secular trends observed for SAWF (Kruskal-Wallis Chi-squared = 4.9320; p = 0.2943). Figure 5.23 illustrates the initial decrease in the total lower limb ratio from 0.531 in the 1940’s to 0.524 in the 1960’s. This is followed by a large increase to 0.546 in the 1990’s. The total lower limb ratio of SAWF remained unchanged from the 1940’s to 1980’s (0.514) with a small increase observed in the 1950’s (0.519).
A similar pattern is observed in the lower limb ratio with a significant positive secular trend for SABF (Kruskal-Wallis Chi-squared = 20.8982; p = 0.0008) while no significant change is observed for SAWF (Kruskal-Wallis Chi-squared = 4.1981; p = 0.3799). Figure 5.24 demonstrates the secular trend in the lower limb ratios between SABF and SAWF. The lower limb ratio of SABF decreased from 0.0.502 in the 1940’s to 0.492 in the 1970’s followed by a large increase to 0.512 in the 1990’s. A small, non-significant increase from 0.479 in the 1940’s to 0.480 in the 1980’s is observed for SAWF.
Figure 5.25 demonstrates a significant positive secular change in the thigh ratio for SABF (Kruskal-Wallis Chi-squared = 117.7335; p < 0.0001) while a non-significant increase was observed for SAWF (Kruskal-Wallis Chi-Squared = 6.7571; p = 0.1493).
Chapter 1: Introduction
Chapter 2: Literature Review
2.1 Allometry and limb proportions
2.2 Evolutionary changes in limb proportions
2.3 Modern studies on limb proportions
2.4 Secular changes in stature and limb proportions
2.5 Secular trends in relative limb proportions
2.6 The implications of secular trends in stature and limb proportions on stature estimation
2.7 Secular changes in bone robusticity and width
Chapter 3: Materials and Methods
3.1. Sample
3.2 Methods
3.3 Statistical analysis
Chapter 4: Ancestry differences and secular trends in anthropometric stature
4.1 Ancestry differences and secular trends in the anthropometric stature of South African population groups
4.2 Differences and secular trends in the anthropometric stature of Southern and Northern hemisphere population groups
Chapter 5: Ancestry differences and secular trends in the anthropometric limb proportions of South African population groups
5.1 Ancestry differences and secular trends in the anthropometric limb proportions of South African black and white males
5.2 Ancestry differences and secular trends in the anthropometric limb proportions of South African black and white females
5.3 Comparisons of the secular changes in the anthropometric limb proportions of South African population groups combined
Chapter 6: Ancestry differences and secular trends in Total Skeletal Height (TSH)
6.1 Ancestry differences and secular trends in TSH of South African population groups 128
6.2 Osteometric differences and secular trends in stature (TSH) of Southern and Northern hemisphere population groups
Chapter 7: Differences and secular trends in the osteometric limb proportions of South African and North American population groups
7.1. Ancestry differences and secular trends in the osteometric limb proportions of South African population groups
7.2 Differences in the osteometric limb proportions between white South African and North American population groups
Chapter 8: Discussion
8.1 Ancestry differences and secular trends in the anthropometric and osteometric stature of South African population groups
8.2 Ancestry differences and secular trends in the anthropometric and osteometric limb proportions of South African population groups
8.3 The implication of secular changes in stature and limb proportions on stature estimations in South Africa
8.4 Limitations of the study and future recommendations
Chapter 9: Conclusions
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