From skulls to soles: Cranial and anthropometric correlations in forensic analysis

INTRODUCTION

Skull bone thickness and its relationship with anthropometric variables like body length and foot length are critical aspects of forensic anthropology and forensic anatomy.^[1] The thickness of the human cranial diploe and its correlation with age, sex, and general body build^[2] and the use of skull anthropometric parameters with height and foot length, for stature estimation, is crucial in forensic investigations.^[1] Skull thickness is a valuable yet underexplored anatomical parameter with significant relevance in both forensic and clinical practice. It contributes to the mechanical protection of the brain and is influenced by factors such as age, sex, genetics, and nutrition. Understanding these parameters has applications in forensic identification, biomechanical studies, and the estimation of physical attributes from skeletal remains. While studies on skull thickness have historically relied on archaeological specimens or imaging techniques, these methods often introduce artifacts or inaccuracies due to the desiccation of bones or limitations of imaging modalities.^[3] In addition, the limitations of imaging techniques, such as computed tomography (CT) scans, can be expensive and may not always be available for field or museum samples.^[4] Previous studies investigating skull bone thickness have often relied on imaging modalities such as CT and magnetic resonance imaging or on archaeological and dry skull specimens. While valuable, these approaches may not accurately reflect the condition of living or recently deceased individuals due to postmortem desiccation or imaging artifacts. For example, radiological techniques used on archaeological materials often fail to capture soft tissue and can be affected by preservation-related distortions. Similarly, imaging methods like reflectance transformation imaging (RTI) have limitations in magnification and may introduce subtle artifacts. Anthropological studies have shown that skull morphology varies not only across individuals but also across populations, suggesting a role for genetic and environmental influences. The importance of skull thickness becomes especially evident in forensic contexts, where it can aid in the reconstruction of trauma, estimation of sex, and identification of unknown individuals. This study seeks to overcome these limitations by examining fresh autopsy cases, providing observations more reflective of the living state of human anatomy. The human skull is a complex structure composed of the frontal, parietal, occipital, temporal, and sphenoid bones, among others, which vary significantly in thickness across different regions and individuals.^[2] Skull bone thickness is influenced by genetic, environmental, and functional factors, including mechanical stress and age-related changes.^[5] Previous studies have demonstrated that these variations are not only region-specific but also exhibit sexual dimorphism, with males typically having thicker cranial bones than females. These differences are relevant for understanding the mechanical properties of the skull and its role in protecting the brain.^[1,2] Foot length and body length are also important anthropometric measures that have been used to estimate stature and other physical characteristics in forensic and anthropological research. Relationships between cranial dimensions and these variables have been explored in various populations, often highlighting population-specific patterns and sexual dimorphism. There are documented norms for cranial dimensions and presented linear regression formulae for stature prediction in adult male and female populations of Southern Punjab.^[6] Similarly, another study assessed the correlation between head length and stature in a Central Indian population.^[7] However, comprehensive studies examining the correlation between skull thickness, foot length, and body length in fresh autopsy cases are limited, especially in the Indian population. Given India’s diverse genetic and environmental landscape, region-specific studies are essential to generate reliable forensic reference data. This study, therefore, aims to explore the structural variability of skull bone thickness in an Indian population using direct measurements taken during autopsy. In addition, it examines the association between skull thickness and other anthropometric parameters such as body length and foot length, which have proven useful in forensic stature estimation and biological profiling. By analysing fresh autopsy cases, this study provides more clinically relevant and population-specific observations that may enhance the accuracy of forensic identification and trauma reconstruction practices.

MATERIALS AND METHODS

RESULTS

The study analyzed data from 127 medicolegal autopsy cases (94 males and 33 females) over a 1-year period. The anthropometric parameters and skull measurements recorded from these cases revealed notable gender-based differences, along with variations in cranial bone thickness at different anatomical landmarks.

Descriptive statistics

The mean age of the study population was 39.9 ± 15.2 years. Males had a mean age of 39.6 ± 15.7 years, while females had a mean age of 40.5 ± 14.2 years. The average body length across all subjects was 164.57 ± 8.20 cm, and the mean foot length was 24.93 ± 2.01 cm. Head circumference was recorded as 52.59 ± 2.48 cm overall. Table 1 summarizes the comparative anthropometric data between male and female subjects. Figure 1 shows males exhibited significantly greater mean body length (166.3 ± 7.44 cm) compared to females (159.61 ± 8.23 cm), with a P < 0.001. Similarly, foot length in males (25.36 ± 1.88 cm) was significantly higher than in females (23.75 ± 1.69 cm), P < 0.001. Head circumference was also significantly larger in males (53.0 ± 2.43 cm) compared to females (51.61 ± 2.38 cm), with P = 0.012.

Table 1: Comparison of cranial and anthropometric measurements between females and males (Mean ± SD) P-values were obtained using the independent samples t-test for comparison between males and females

Characteristic	Female, n=33	Male, n=94	P-value
Age	36.091 (14.442)	39.021 (14.111)	0.323
Head circumference	51.212 (2.954)	52.822 (3.070)	0.012
Height (body length)	151.033 (26.536)	167.014 (7.784)	<0.001
Foot length	8.555 (0.489)	9.515 (0.995)	<0.001
Right frontal eminence	0.653 (0.231)	0.739 (0.622)	0.538
Left frontal eminence	0.703 (0.246)	0.661 (0.258)	0.468
Right parietal eminence	0.628 (0.240)	0.672 (0.269)	0.410
Left parietal eminence	0.691 (0.268)	0.667 (0.255)	0.740
Right pterion	0.356 (0.181)	0.352 (0.133)	0.471
Left pterion	0.403 (0.210)	0.358 (0.137)	0.565
Occipital prominence	1.219 (0.400)	1.177 (0.385)	0.501
Bregma	0.668 (0.256)	0.729 (0.306)	0.346

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Figure 1:

Correlation matrix and distribution plots showing relationships between cranial and anthropometric measurements stratified by sex. The plot includes scatterplots, density distributions, and Pearson correlation coefficients between variables such as height, head circumference, foot length, and skull thickness at various anatomical landmarks (frontal, parietal, pterion, and occipital regions). Red indicates female data and blue indicates male data. Significant correlations are marked with asterisks (P<0.05, P<0.01, P<0.001). Sex-based differences in variable distributions are visible in both univariate and bivariate comparisons.

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DISCUSSION

The study provides novel insights into the structural variability of human skull bones and their associations with anthropometric parameters such as body length and foot length. Previous studies have largely relied on archaeological specimens or imaging techniques, which may not accurately reflect the condition of living or recently deceased individuals due to desiccation or imaging artifacts. For instance, radiological analyses on archaeological material, such as X-rays^[8] and CT scans, are often used to study mummified or skeletonized human remains without damaging them.^[9] However, these methods can introduce artifacts or fail to capture the true state of biological tissues because of long-term preservation. Similarly, RTI^[10] has been applied to study bone surface modifications, but it, too, can be limited by the degree of magnification and potential imaging artifacts.^[11] By focusing on fresh autopsy cases, this research bridges a crucial gap, offering more precise and clinically relevant observations. The findings reveal significant gender differences in skull thickness, body length, and foot length. Consistent with earlier studies, males demonstrated larger head circumferences, greater body length, and longer foot lengths than females, highlighting the sexual dimorphism in cranial and skeletal dimensions.^[12]

For example, research by Talokar and Lade found significant differences in cranial length, breadth, and height between male and female skulls.^[12] Similarly, Singh et al. reported that male skulls had a higher mean cranial capacity compared to female skulls.^[13] The observed differences in skull thickness at various anatomical landmarks also align with the existing literature, which emphasizes the variability of cranial bone thickness across individuals and populations.^[14] The thicker right frontal eminence in males and the significantly thicker left frontal eminence in females corroborate findings in studies that suggest localized gender-specific adaptations in cranial architecture.^[15] For instance, research by Bulut et al. found significant differences in cranial bone thickness between genders using three-dimensional scanning techniques.^[16] Similarly, a study by Kamali and Murugan highlighted the variability in facial soft tissue thickness across different anatomical landmarks.^[14] While males generally exhibit thicker skulls, localized differences such as a thicker left frontal eminence in females may result from individual or environmental factors, suggesting caution in overgeneralizing sexual dimorphism (Kamali and Murugan, Bulut et al.).^[14,16] The lack of uniformity in skull thickness noted in this study is particularly noteworthy. This irregularity has significant implications for forensic investigations and biomechanical studies. For instance, variations in thickness at specific points can influence the skull’s resistance to trauma, potentially aiding forensic experts in reconstructing injury patterns. Understanding skull thickness distribution is vital when interpreting cranial fractures and impact sites, especially in blunt force trauma cases. Thinner regions may fracture more readily, which can help in estimating the direction, force, and nature of the impact, as well as distinguishing between accidental and non-accidental injuries. These site-specific thickness patterns can be integrated into biomechanical models to simulate head trauma under different conditions, thereby strengthening medicolegal conclusions in courtrooms. Furthermore, the correlations between skull bone measurements and anthropometric parameters like body length and foot length provide a basis for estimating stature in forensic and anthropological contexts. These relationships can be particularly useful in cases where only partial remains are available. The findings may also assist in sex estimation and population profiling in forensic scenarios. Incorporating cranial thickness measurements as supplementary data in combination with traditional skeletal markers may enhance the reliability of forensic identification, especially in mass disaster or decomposition cases where DNA analysis may not be immediately available. Similar relationships have been documented in population-specific studies, suggesting that such associations may hold universal applicability. However, the development of region-specific anthropometric databases remains crucial to improve the precision of forensic applications, particularly in diverse populations like that of India. The study has limitations that warrant consideration. The relatively small sample size and the restriction to a single geographical location may limit the generalizability of the findings. In addition, while the study accounted for gross pathologies and deformities, subtle congenital or acquired factors affecting skull morphology may have been overlooked. Future studies should aim to expand the sample size, include diverse populations, and explore the potential genetic and environmental determinants of skull thickness and its associations with other anthropometric variables.

CONCLUSIONS

This study offers valuable insights into the variability of skull bone thickness and its associations with anthropometric parameters such as body length and foot length in an Indian population. Statistically significant differences were observed between males and females in terms of body size and cranial dimensions. While males exhibited larger overall measurements, including head circumference, body length, and foot length, the finding of a significantly thicker left frontal eminence in females highlights the complexity and site-specific nature of sexual dimorphism in cranial architecture. The non-uniform distribution of skull thickness has important forensic implications. It can assist in sex estimation, stature reconstruction, and cranial trauma analysis, particularly in cases involving incomplete or degraded remains. The observed correlations between cranial and bodily dimensions provide population-specific reference data that can strengthen forensic identification protocols and anthropological profiling in the Indian context. However, the inconsistent patterns of sexual dimorphism observed, such as localized cranial thickness variations, suggest that skull measurements should be used cautiously and in conjunction with other parameters for sex determination. Rather than serving as standalone indicators, skull thickness measurements may offer the most forensic value when integrated into multifactorial models. Future research with larger, more diverse samples is essential to refine these observations and better understand the genetic, environmental, and biomechanical influences on cranial morphology. This study lays the groundwork for such efforts and underscores the importance of incorporating region-specific anatomical data into forensic practice.