In many instances when bodies of victims are recovered, typically, they are at different states of dismemberment and stages of decomposition. The forensic anthropologist faces the immediate dilemma of determining the true identity of the individual. When the surviving foot is all that is available in determining partial identity, to reliably estimate stature from anthropometric foot dimensions, the validity of predictive regression model must rest on its simplicity of measurement, applicability, and accuracy in prediction (Kanchan et al. 2008).
We painstakingly and comprehensively documented the anthropometric protocol adopted for this study. This is because the protocol recommended by the International Society for the Advancement of Kinanthropometry is globally recognized for its simplicity of implementation, the highest quality of the equipment, the accuracy and precision of the measurements, and the strict adherence to practice standards of quality assurance through rigorous training of all members of the research team. The lead author is an ISAK certified anthropometry technician level 2 (Accreditation: Potchefstroom, South Africa, 2006).
Variation in stature and foot dimensions among populations
The mean stature and foot dimension values were recorded for the present study, with stature values ranging from 164.71 ± 6.70 to 176.44 ± 6.47 cm; and foot dimension values ranging from 9.49 ± 0.73 to 27.29 ± 1.30 cm in the males, females, and the pooled sample. When compared with the values obtained from similar studies in other climes, it can be observed that stature and foot dimension values from the present study are greater than values reported by Ozden et al. (2005) and Zeybek et al. (2008) in Turkey, Krishan and Sharma (2007) on North Indians, Mansur et al. (2012) on adult Nepalese, Dhaneria et al. (2016) on Indian Rajasthans, and Kim et al. (2018) on South Korean males and females. These findings further validate the observation by Hossain et al. (2010) that higher values in anthropometric dimensions are obtainable in negroid populations. While these differences could be explained in part by population-specific genetic variation, varying morphological features such as foot sizes would likely depend upon geographical distribution and primary racial characteristics (Shukla et al. 2017). These inter-populational differences in anthropometric dimensions necessitate the establishment of population-specific algorithms for stature prediction from foot dimensions. More importantly, however, the finding is consistent with the Allen’s rule of evolutionary physiological adaptation. In 1877, the American biologist Joel Allen had observed that the length of arms, legs, and other appendages also has an effect on the amount of heat lost to the surrounding environment. Thus, among warm-blooded animals, individuals in populations of the same species living in warm climates near the equator tend to have longer limbs than do populations living further away from the equator in colder environments due to the fact that a body with relatively long appendages is less compact and subsequently has more surface area (Allen 1877). The greater the surface area, the faster body heat will be lost to the environment. This same phenomenon can be observed among humans. Hence, Africans living in the tropical rain forest tend to have larger feet.
Sexual dimorphism in stature and foot dimensions
Gender differences in stature and foot dimensions were found to be statistically significant (P < 0.05) in the present study, with males exhibiting greater anthropometric values than the females. Similar views have been expressed by Krishan and Sharma (2007), Zeybek et al. (2008), Uhrova et al. (2015), and Kim et al. (2018) as they all reported the existence of sexual dimorphism from their studies on Indian, Turkish, Slovak, and Korean adult populations respectively; hence, indicating that there exist statistically significant differences in foot length and breadth between the male and the female subjects in their various studies. The reason for the greater values in anthropometric dimensions in the males can be ascribed to the fact that fusion of epiphyses of bones occurs earlier in females in comparison to males, as the latter has two more years of bony growth than the former. Hormonal influences during puberty causes earlier cessation of bony growth in females than the males, as it has underlying effects on the pattern and duration of growth. The females undergo accelerated pubertal growth spurt, ending their growth faster than the males who experience more sustained growth (Ansah et al. 2017). Frey (2000) also reported that women generally tend to have a narrower heel in relation to the forefoot and narrow feet than men relative to length.
Bilateral asymmetry in foot dimensions
The present study found the foot length and breadth of the females and the pooled sample to be bilaterally asymmetric, as there exist statistically significant (P < 0.05) bilateral differences between the right and left sides. The foot length in the males exhibited no significant bilateral difference, though the foot breadth did. Our findings on the females, pooled sample, and the males (foot breadth) are not in line with the reports of earlier studies which reported the non-existence of statistically significant bilateral asymmetry in foot dimensions from studies in different populations (Ozden et al. 2005; Krishan and Sharma 2007; Zeybek et al. 2008; Uhrova et al. 2015). Kanchan et al. (2008) also reported from their study on Gujjars of North India that although the mean foot dimensions were dominant on the left side in the males and on the right side in the females, the difference between the sides was statistically insignificant for all the dimensions except for foot breadth in the males. To explain this observation, it has been suggested that right-foot dominance in object manipulation and other activities including sports confers greater motor coordination, while the non-dominant side usually serves mainly for postural and stabilizing support during ordinary activity and may thus be subjected to greater mechanical load than the dominant limb, resulting in a heavier and longer non-dominant limb (Krishan et al. 2010). This theory, however, does not appear to hold for our study, as the dominant foot (right foot) showed greater anthropometric values than the contra-lateral side, except for the foot length measures in the male sample exhibiting bilateral symmetry. This bilateral symmetry in foot length for the male subjects in our study could partly be explained by the observation that more than 80% of the participants admitted to regularly engaging in football games. More than 90% of them were right-footed. This, in all probability, may have resulted in increased growth of the right foot, thus eliminating the growth preponderance of the non-dominant left foot.
Correlation of stature with foot dimensions
From this study, the foot length exhibited higher correlation coefficient values than the foot breadth in the males, females, and the pooled sample of the present study. This is in tandem with the findings of Ozden et al. (2005), Krishan and Sharma (2007), Kanchan et al. (2008), Zeybek et al. (2008), Ozaslan et al. (2012), and a host of other authors from studies predicting stature using foot dimensions. For foot length, higher correlation coefficient values than was recorded from this study were reported by Dhaneria et al. (2016) on adult Rajasthans, Krishan and Sharma (2007) on Rajputs of North India, and Uhrova et al. (2015) on adult Slovaks. This implies that the aforementioned authors recorded higher association between stature and foot dimensions than was obtainable from the present study. When both sexes were considered separately, the present study found the maximum correlation between stature and foot length to exist for the left foot length of the female population; a finding which is congruent with that of Uhrova et al. (2015). On the contrary, Ozden et al. (2005), Krishan and Sharma (2007), and Kanchan et al. (2008) reported maximum correlations between stature and foot length in the left, right, and left foot lengths of the male sample in their respective studies.
For the foot breadth, Kanchan et al. (2008) and Dhaneria et al. (2016) recorded higher correlation coefficient values than was done for the present study, which shows that their respective studies exhibited higher association between stature and foot breadth than for the present study. Lesser correlation coefficient values of stature and foot breadth than was recorded for the present study were reported by Ozden et al. (2005) and Krishan and Sharma (2007) which indicates higher association between stature and foot breadth in the present study. The left foot breadth in the males exhibited the highest correlation in the present study when both sexes were considered separately. This is in keeping with the reports of Ozden et al. (2005) and Krishan and Sharma (2007). In contrast, Kanchan et al. (2008) in their study on adult Gujjars reported the right foot breadth in the females to have the highest correlation with stature, an observation which is not in tandem with the findings of the present study.
Regression equations and multiplication factors for stature estimation
Standard errors of estimate (SEE) values from the regression equations devised for stature prediction from foot length and breadth of the males, females, and the pooled sample of this study were recorded. For foot length, it was observed that the least SEE was shown by the right foot of the male subjects, while the left foot in the females showed the second lowest SEE value. This implies that the right foot length of the males is the most reliable parameter for stature estimation from the present study, followed by the left foot length in the female sample. In contrast, Krishan and Sharma (2007) in their study on Rajputs of North India reported that the left foot length of the female sample provided the most accurate prediction for stature, while Kanchan et al. (2008) found the right female foot breadth to be the most reliable predictor of stature in adult Gujjars, with the least SEE value. For foot breadth of the present study, it was observed that the left foot breadth in the males recorded the least SEE value, showing the highest reliability in stature prediction when foot breadth is considered. Krishan and Sharma (2007) and Kanchan et al. (2008) reported the right and left foot breadth in the female samples of their respective studies to be the best predictors of stature when the foot breadth is considered, and their findings are not congruent with the reports of the present study. Generally, the male sample of our study predicted stature more accurately using foot dimensions than the females, with a lower range of SEE values (± 4.682 to ± 5.979); when compared with the females with SEE values ranging from ± 4.715 to ± 6.319. This is not in agreement with the findings of Krishan and Sharma (2007) and Kanchan et al. (2008) which reported the female sample to exhibit the lowest range of SEE values from their respective studies.
Kanchan et al. (2008) reported lower multiplication factors for foot length and breadth in adult male Gujjars when compared with the values recorded for the males of the present study. However, the female Gujjars recorded higher values when compared to the female sample of the present study. This shows that adult male Gujjars have higher stature to foot dimension proportion than adult Nigerian males, while the female Gujjars have lower proportion when compared with their Nigerian counterparts. The present study also recorded greater values of multiplication factors in the females than the males, a report which is congruent with the finding of Kanchan et al. (2008) on a North Indian population.
The present study has demonstrated the utility of stature estimation standards developed from foot dimensions of an adult Nigerian population of different ethnicities in Lagos, Nigeria. This is very imperative as Lagos, the most complex metropolitan center of regional population and organization in Nigeria, the commercial capital, and the most significant city in the country, is home to many Nigerians of different ethnicities and backgrounds. The findings from this study will have important applications in the formulation of biological profiles during forensic investigations and disaster victim identification through the provision of multiplication factors and regression equations for stature prediction from foot dimensions.