Introduction:
Dermatoglyphics or epidermal ridge configuration is the study of dermal ridges on palms, fingertips, and soles (1). These epidermal ridges are formed in early embryonic life, around 10 weeks of post fertilization and remain unaltered throughout the life, except for an increase in size in parallel with the general growth of the individual (2). The
palmar friction ridges are the corrugated wavy skin patterns with sweat glands but no oil glands or hair. Discontinuities in the
palmar ridge patterns are called the flexion creases. Flexion creases appear before the formation of
palmar friction ridges during the embryonic skin development stage, and both of these features are claimed to be immutable, permanent, and unique to an individual (3). The structure of the epidermal ridges and their arrangement on the hand was first described by Nehemiah Grew, in 1684 (4). Herschel for the first time (1858) captured the systematic images of hand, finger and palm, and used it in identification purposes (5). Later, Sir Francis Galton highlighted the use of fingerprint patterns,
palmar ridges and creases in personal identification (1). Cummins and Midlo observed that the width of a palmar ridge is 18 % larger compared to a finger. So, they explained the importance of the ‘palmar flexion crease based identification’ (6). Presently, the
palmar creases are very helpful in revealing anthropologic characteristics and diagnosing chromosomal aberrations (7).
Palmar pattern configuration:
Palmar flexion creases were distinguished into several anatomically designed creases. The configurations are associated with the tri-radii (Galton's deltas); which consists of three ridge systems converging with each other at an angle of roughly 120º (Y -shaped group of ridges) (8). The palm of each hand contains five tri-radii and four of them are found at the base of the second to fifth fingers (digital areas) and are called a, b, c & d tri-radii, respectively (see Figure 1). The fifth tri-radius is located near the base of the fourth metacarpal and it is called axial tri-radius or ‘t’ tri-radius (9). Dermal ridges of the digital areas of the palms are often counted between two triradius. The most frequently used ridge count is obtained in-between ‘a’ and ‘b’ tri-radii, which is referred to as the a-b ridge count (10).
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Figure 1: Left Hand Showing A-B Ridge Count |
a-b ridge count:
Fang TC for the first time (1950) studied the distribution and inheritance of the a-b ridge count on
palmar ridge (11). Later, several researchers (11-19) have analyzed the genetic determinants of a-b ridge count. a-b ridge counts also had been used to study the population variability (19-21) and to diagnosis and confirm certain diseases (19,22-25).
In India, some publications on the a-b ridge count in different groups of population are available (9,26-33). But, on those studies, the attention was mostly on the inheritance patter, fluctuation asymmetry and the association with disease state. There is a dearth of information in the sexual dimorphism of a-b ridge count. David TJ (1984), for the first-time focused exclusively on the distribution and sexual variation of a-b ridge count in the United Kingdom (34). This study found that the a-b ridge count distribution in males was significantly different, while in females the variation did not reach statistical significant. But we need more prospective research studies to obtain detail knowledge about the unique distribution pattern of a-b ridge count. Till now, several methodologies are used in forensic science for personal identification to solve the criminal cases in legal processing. In India, law enforcement highly used the finger print pattern for identification (35). The
palmar dermatoglyphics, particularly a-b ridge count can also be used as a tool for personal, because it is accessible and easy to measure. The present study aims to understand the distribution and sexual dimorphism of the a-b ridge count between males and females among the ‘Bhil’ tribal community of Mount Abu, Rajasthan state, western India.
Materials and Methods:
The present study was a cross sectional study on community dwelling ‘Bhil’ tribal population aged 10 years to 60 years.
Study area and people:
Mount Abu is a hill satiation in the Aravalli hill range in Sirohi district of Rajasthan state, western India (see Figure 2). Rajasthan is India’s largest state by area. The present study was carried out in the home setting of the rural villages of Dilwada, Gora-Chapra, Kala-Chapra, Bande, Filter-house, Pokhran-house in the block Mount Abu. A major portion of this block is dominated by the tribal communities and the majority of tribal population is dominated by ‘Bhil’.
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Figure 2: Study Area |
Study design:
A total 241 (122 males and 119 females) individuals were selected by random sampling. Inclusion criteria for this study are: i) age group 10-60 years, ii) both male and female, iii) without any chromosomal deformities, infections and burn in the palm. The ‘Bhil’ tribal community have been chosen purposively due to numeric dominance in Mount Abu.
The exclusion criteria for the participants included: i) any deformities of palm and infected hand, ii) chromosomal abnormalities like Klinefelter’s syndrome, Turner’s syndrome etc. and iii) deep burns of palms leading to scars.
The participants were explained about the objectives of the study and were asked to sign a consent form only when they had fully understood the purpose to study and the procedures to be undertaken for the study before data collection. General information for the identification viz. name, age, sex, caste, address was also collected.
Dermatoglyphics- Ink printing procedure:
The standard procedure (6) of ink printing method was used to obtain the dermatoglyphics configuration. Each individual was asked to clean and dry their hands, leaving some moisture. Then, using the cotton pad, the required amount of ink was placed on the glass slab and uniformly smeared it with the help of ink rubber until a thin film was obtained. After that, this thin film of ink was applied uniformly on the palm of the subject by placing inked cotton pad. The zone of the flexion crease at the wrist, the ulnar margin, the metacarpal phalangeal crease and the central hollow portion of palm were uniformly inked with special attention. Each hand of the subject was then placed on a sheet of paper from proximal to distal end, and then gently pressed between inter-metacarpal grooves at the root of fingers and on the dorsal side corresponding to thenar and hypothenar regions. The palm was then lifted from the paper in the reverse order from distal to proximal end. The print was subsequently visualised with the use of a magnifying lens.
a-b ridge count:
The a-b ridge count (ABRC) has been evaluated following standard technique (36). It refers to the number of ridges between tri-radii ‘a’ and ‘b’ (see Figure 1). The total a-b ridge count (TABC) was calculated by adding both the left and right ridge counts. Thereafter, it is also classified as ‘low value’ and ‘high value’ as per the definition of Fang (1950) (37). The a-b count is termed as ‘low’ if it is ≤78 and ‘high’ if the count >78.
Data analysis:
The data obtained was subjected to statistical analysis using SPSS version 22. The parameters taken were analysed through descriptive statistics to find out the frequency, mean and standard deviation. For inferential statistics, the student t-test was used to test significant differences between male and female variables. The level of significance was taken at p<0.05
Results:
The distribution and sexual variation of total a-b ridge count (TABC):
The study comprises 241 individuals, and the major studied individuals are belonged to the TABC group 70-79 and 80-89. The TABC group 0-39, 110-119 and 120+ do not possess any individuals. It is seen that only 1.7% participants belonged to the 40-49 group and they all were female. Among the male, maximum (36.9%) individuals belonged to the TABC group 70-79. On the other hand, for females, it was highest (41.2%) in the 80-89 group. The mean TABC of the studies individuals was higher in males (80.7) than females (78.5), but it does not possess any statistical significant. According to Fang TABC classification, total a-b ridge count was ‘high’ for both the sex (see Table 1 and Figure 3).
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Figure 3: Distribution of Total a-b Ridge Count (TABC) |
Table 1: The Distribution of Total A-B Ridge Count (TABC) |
TABC |
Males (N=122) |
Females (N=119) |
t-test |
p-value |
| |
Number |
Percent |
Number |
Percent |
1.795 |
0.074 |
0-39 |
- |
- |
- |
- |
40-49 |
- |
- |
2 |
1.7 |
50-59 |
2 |
1.6 |
2 |
1.7 |
60-69 |
12 |
9.8 |
11 |
9.2 |
70-79 |
45 |
36.9 |
47 |
39.5 |
80-89 |
41 |
33.6 |
49 |
41.2 |
90-99 |
17 |
13.9 |
6 |
5.0 |
100-109 |
5 |
4.1 |
2 |
1.7 |
110-119 |
- |
- |
- |
- |
120+ |
- |
- |
- |
- |
Mean |
80.7 |
78.5 |
SD |
9.8 |
9.3 |
SE |
1.0 |
0.9 |
Note: SD; Standard Deviation. SE; Standard Error. p-value; significant value |
Sexual dimorphism of a-b ridge count (ABRC):
Table 2 displays the comparison of a-b ridge count among the male and female. The mean ABRC value was higher for male than female on both the hands. t-test found that the mean difference of right hand ABRC was significantly higher in male than female (t=2.40, p=0.017). But in left hand, the difference between male (40.5) and female (39.9) was not statistically significant.
Table 2: Comparison of A-B Ridge Count (ABRC) among Male and Female |
ABRC |
Right Hand |
Left Hand |
| |
Mean |
SD |
Mean |
SD |
Male (n=122) |
40.1 |
5.0 |
40.5 |
5.6 |
Female (n=119) |
38.5 |
5.4 |
39.9 |
4.7 |
t-test |
2.40 |
0.91 |
p- value |
0.017** |
0.364 |
Note: SD; Standard Deviation. p-value; significant value
**. Significant at <0.05 level |
Discussion:
The variation among males and females in the total a-b ridge count (TABC) is very small, and thus are statistically insignificant. David TJ in his study also analysed the distribution of summed (right plus left) a-b ridge count in 1,000 healthy subjects which showed a similar distribution pattern with no significant sex difference. The reason behind that the smaller influence of sex chromosome complements on the a-b ridge count than the effect of same on finger ridge count. The total a-b ridge count is probably also less genetically determined than the total finger ridge count (34).
Several past studies have hypothesised that the fingerprints of women have ‘fine’ epidermal ridge details while the men have ‘course’ ridge details, which possess the utmost of ridge count in male than female (38). In our study, we also observed the quantitative variation of
palmar epidermal ridge count between two sex groups. Male have the higher palmar ridge count than the female, and in right hand the variation is also statistically significant. Igbigdi and Msamati (1999) conducted a study to establish palmar and digital dermatoglyphics pattern of Malawians and they also concluded that males have significantly higher a-b ridge counts than females (39). Arrieta et al. (1992) tried to find out the reason behind the sexual variation and concluded that the ‘a-b ridge count’ in males seems to be more influenced by environmental factors than the other
palmar ridge counts; but in case of females, it was found that a-b ridge count was influenced by genetic component (40).
In India, Joshi et al. (1992) studied fifty persons, who had nasobronchial allergy and compared it with age and sex-matched normal individuals for dermatoglyphics
palmar patterns, where he also found that the a-b ridge count (ABRC) was higher in males (41). In a very recent study, Das et al. (2014) studied palmar a-b ridge count in E-β thalassemia patients on the Bengalee Hindu caste populations of West Bengal, India. They also found that the distribution of TABC was highest in males compared to females in both E-β-thalassemia patients and other populations (33). Moreover, the a-b ridge count varies between two sex groups, but we need more population specific studies and particularly on healthy population to improve our understanding regarding the distribution and sexual variation of a-b
palmar ridge count and its applications.
Palmar ridge configurations include much more information than finger, and therefore we can use it to compensate the finger print deficiency. Presently,
palmar prints are extensively used in research studies to find its association with geographical distribution, temperament, health, intelligence and heredity, etc (10). Despite increasing use of the a-b ridge count in research studies over the past few decades, there is a lack of consensus in the literature regarding its distribution and pattern of sexual variation. Most of the studies were conducted in disease population or in hospital setting. Thus this paper offers new research perspectives and highlighted the need to understand the application of a-b ridge count for personal identification in forensic science.
This study has number of strengths. This is an original study conducted in a particular tribal community in Indian population and it includes the most important ridge count, which is broadly used as indicators for several human’s biological and anatomical aspects. The limitations of our study is that we had limited sample size, as it was focusing on a particular community and healthy population; the adults of the community were usually unavailable as they use to leave very early in the morning for agricultural work and we had to exclude many adults form both the sex groups due to the deformities on their
palmar ridges. Moreover, there are very few studies available on a-b ridge count for Indian populations and especially those are community based, which makes this present study an important contribution in forensic anthropological research.
The present study concluded that a-b ridge count was maximum for male than female. The mean value of a-b ridge count on the right hand was significantly higher in male than female. This can provide a basic understanding of unique and important characteristics of a-b ridge count. The current study highlighted the need of more multidisciplinary studies to obtain knowledge about distribution pattern and sexual variation as well as to find out the reason behind it. There after we can use it as an identification tool in forensic science. Unfortunately, in India, there is a scarcity of data in terms of a-b ridge count, so these findings offer complementary research perspectives for further research.
Acknowledgements:
We acknowledge to all the participants who contributed to the study for their cooperation and help during fieldwork. Moreover, acknowledgement is also owed to the Department of Anthropology, the University of Delhi for providing all the necessity for the present study.
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