Hand analysis has fascinated researchers throughout history. In recent times, two aspects of the human hand have drawn attention for observation and analysis including dermatoglyphic ridge pattern and, secondly, finger lengths and their ratios. The present study is unique as for the first time, it presents information on 2D:4D and hand patterns of both sexes in students of Malaysian ethnicity. Digit ratio is sexually dimorphic and can be used as a window for in utero exposure to androgens, primarily testosterone (Jeevanandam and Muthu 2016). However, there is no harmony on the intra-sexual and inter-sexual variations in digit ratios and traits across various ethnic groups. The morphological gender difference reported is that male fingers are significantly longer as compared to female fingers (Williams et al. 2000; Lippa 2003). In females, the index and ring fingers are reported to be almost of equal length, while in males, the ring finger tends to be longer than the index finger. The 2D:4D ratio is lower in men as compared to women (Setiya et al. 2017). However, in our study, we observed that the ring finger was longer than the index finger in both males and females which indicates that the digit ratio varies depending on various populations and geographic distribution. Many studies have reported the existence of significant sex differences in 2D, 4D, and its ratio in different ethnic populations and its bilateral variations among individuals (Voracek et al. 2008; Krishan et al. 2013; Sen et al. 2014). Sex differences in the digit ratio can be a valuable indicator mainly when DNA analyses cannot be performed (Aboul-Hagag et al. 2011).
Results of the present study on hand patterns based on digit ratio indicated that hand pattern A (2D<4D) was the most prevalent trait among Malaysians seen in both their right and left hands which indicates that no significant difference exists between the ethnic groups of Malaysia. Similar results have been obtained in previous studies involving different study populations such as China (Xu et al. 2015), Nigeria (Gwunireama and Ihemelandu 2010), Italy, and Romania (Tomulescu and Nicoras 2015). Thus, it is possible that significant differences are more likely to be observed when comparing races from different countries along different latitude than ethnic groups or tribal groups. In the view of such contradicting results, more studies are needed to verify this claim.
The available literature and data from recent research indicate accumulating evidence on 2D:4D ratio showing correlations with various phenotypic traits and health in humans. Males with higher digit ratio are said to be more prone to have low sperm counts, augmented the risk of heart disease, obesity, and metabolic syndrome (Oyeyemi et al. 2014). Higher digit ratios in males also showed a correlation with eating disorders, anxiety, and depression (Manning et al. 2013). Low digit ratio is linked with certain characteristics like aggression in males and assertiveness in females (Hampson and Sankar 2012). Martel et al. 2009 reported the male vulnerability to behavior disorders in children and female vulnerability to emotional disorders in adolescence. This evidence suggests the positive relationship between hand patterns and health. Hand patterns have also shown the potential to narrow down the search to particular sex and give the right direction to the ongoing forensic investigation. Studies have focused on the role of hand and foot measurements in establishing the biological profile of individuals in the forensic investigation (Kanchan et al. 2010; Kanchan and Krishan 2011). However, its utility is limited in forensic casework as it is shown to vary between different populations. Hence, the technique of measuring hand patterns might be beneficial in situations where no other means of sexing are available like in the case of war, natural calamities, in a bomb blast, and accidents (Dey and Kapoor 2016). Identification of sex of human remains can immensely help forensic experts while dealing with dismembered and fragmentary remains and in a criminal investigation by reducing the pool of possible victim matches (Dey and Kapoor 2016). Due to the dimensional diversity of the individual body, anthropological measurements of an individual may not be steadily credible tools for discrimination of sex. Therefore, determination of sex through indices like hand patterns and digit ratios can be additional credible tools in sexual dimorphism. In developing countries, this method of hand pattern estimation based on digit ratios can be highly useful for identification especially considering its cost-effectiveness.
Limitations of the study include small sample size, and the focus was only on the Malaysian population. More robust studies on large samples and between different nationalities can help establish meaningful associations between digit ratios and sexually dimorphic traits. This study included a comparison between participants of the same age groups. Hence, these findings cannot be compared with children or the elderly population.