The results of the study indicate that the oval-shaped ear was present among about 40% of the males and 44.8% of the females in the study sample. The other types of ear such as oblique, rectangular, round, and triangular were also found in both the sexes. Bilateral asymmetry exists as regards the shape of the ear. The size and shape of the tragus also vary with respect to the left and right sides as well as sexes. The earlobe showed different characteristics in different individuals. In nearly half of the cases in both males and females, the earlobe was found to be attached to the face; in many cases, it was free and some partially attached. Then, the size and shape of the earlobe also showed variations with respect to sides as well as sexes. The shape of the helix varies in individuals showing certain characteristics such as concave, rolled, flat, and wide covering scapha. The Darwin tubercle showed a variety of structures in both the left and right sides in both sexes. The extensive variability of the human ear may be attributed to the unique structure and characteristics of the ear. Previous studies (Cameriere et al. 2011; Guyomarc'h and Stephan 2012; Swift and Rutty 2003; Singh and Purkait 2009) have also shown that the variability of the external human ear in individuals is enough to enable individualization in forensic examinations and may help to solve the question whether a certain suspect could be identified as being offender. All these variable features and individualistic/special characteristics of the ear may also help in individualization of the person in the CCTV footage of the crime scene (Hoogstrate et al. 2001).
A few studies are available in the literature (Rubio et al. 2017; Cameriere et al. 2011; Purkait 2016; Verma et al. 2016; Vanezis et al. 1996; Purkait and Singh 2008; Alexander et al. 2011; Kearney 2003) regarding the morphological characteristics of the ear which enhance the anthropological and forensic knowledge about the ear and its variability in different populations. The results of the morphological features of the ear in the present study can be compared with a few similar studies conducted worldwide. According to Van der Lugt (2001), the Dutch males were found to possess 68.7% of oval-type ears and Americans have 65% of oval-type ears in both sexes as observed by Iannarelli (1989) as compared to the subjects of the present study (nearly 40–46%). However, generally, the oval-type ears are present more often than the any other types of ears in almost all these studies. The frequency of rectangular ears among the present study (2–9%) was comparable to Dutch (9.1%) but higher than in the Americans (3%) as reported by the authors. The findings related to round-type ears in the present study males (20%) and females (17–18%) can be compared to the Dutch males (3%) and the Americans (2%). Chattopadhyay and Bhatia (2009) observed that Indian Brahmin males have a higher percentage of oblique type ears (63.89%); on the other hand in the present study, the males have 22–29% of oblique-type ears. They further reported 27.19% of long and narrow ears, 46.49% medium ears, 26.31% short and broad ears, and 36.11% vertical type of ears in their study. Singh and Purkait in their study on the Central Indian population reported 47–52% oval-type ears, 26–30% rectangular type, 26–35% triangular-type ears, and 23–59% round type of ears; the trend is somewhat different and erratic from the findings reported in the present study.
As far as the variability of the structure of the helix is concerned, the helix shows a variety of structures. In the present study, nearly half of the subjects (44–51%) possess normally rolled helix; however, Farkas (1978) found 76–79% of normally rolled helix in Americans, while Singh and Purkait (2009) observed 56–60% normally rolled helix in Central Indian subjects. The concave marginal type was found among about 28–48% in the present study; however, Singh and Purkait (2009) observed this character among 10–11% of their subjects and North Americans also possess this character rarely (25%). The frequency of wide covering scapha was found to be very low in North American males (5.20%) (Farkas 1978) and Central Indians (6.42%) (Singh and Purkait 2009) and comparable to about 4.4% as observed in the present study. On the other hand in the females of the present study, the frequency of the character was 19.5 to 20.7%, much higher than those of Central Indians (3.28%) and Americans (5.15%). The frequency of the flat helix was found to be quite comparable with Central Indians and Americans.
The earlobe also shows a variety of characteristics in different populations. The attached earlobe was found in more than 50–56% in the subjects of the present study; however, Singh and Purkait (2009) observed 19–24% in Central Indian population and Farkas (1978) reported 2–3% in Americans. On the other hand, American Whites and Dunker isolates (Gable 1958) have 40.53% and 25.30% attached earlobes respectively, a figure much closer to the subjects of the present study. Free earlobe was found among 41.1% males and 33.3% females on the left ear and 10% males and 9.2% females on the right ear of the present study. This shows significant bilateral differences with respect to this trait. Singh and Purkait (2009) reported 53.71% free lobes in males and 62% in females; Bhowmik (1971) observed free earlobes among Brahmin males (77.5%) and Muslim males (78.4%).
Darwin’s tubercle is an important structure of the ear which is considered to have some evolutionary significance (Loh and Cohen 2016). It can be described in various conditions/categories such as nodosity, enlargement, and projection. Bertillon (1893) described four conditions of Darwin’s tubercle, i.e., nodosity, enlargement, projection, and tubercle. In the present study, the Darwin’s tubercle was not only found on the posterior part of the helix but on the superior helix also. In Central Indian population (Singh and Purkait 2009), the frequency of nodosity was the highest, i.e., 54–62%, which can well be comparable to the present study, i.e. 46–67.8%. In the present study, the Darwin tubercle was absent in just 3.4% of the population; otherwise, it is present on the ear of the subject in one or the other form, however, Singh and Purkait (2009) showed it to be absent among 54–60% of the population. According to Rubio et al. (2015), Darwin’s tubercle does not show sexual dimorphism in Spanish population. Gurbuz et al. (2005) also observed the same findings in Turkish population. However, the Indian studies (Singh and Purkait 2009) including the present one indicate that the Darwin tubercle is present more often on male ears than the females but the sex differences are not significant.
A variety of the structures of these morphological features of the ear may be helpful in personal identification in forensic examinations. However, these features are not sufficient to establish the personal identity; this kind of evidence may always be corroborated with some other indications present at the scene of crime.
Using computer forensics, different methods of ear identification have been developed which may be helpful in extracting and identifying the ear images from CCTV cameras and other surveillance systems (Emersic et al. 2017; Yuan and Chun Mu 2012; Kumar and Wu 2012; Kumar and Chan 2013). However, the modern system of identification using new computerized techniques such as automatic identity recognition and local information fusion by ear images is based upon some computerized algorithms; however, they must be compensated with the anthropological knowledge-based morphological variations. We need to isolate endogamous communities and ethnicities based upon the special characteristics of the ears so that these characters can be combined with computerized algorithms for identification purposes.
A recent genome-wide associate study (Adhikari et al. 2015) published in Nature Communications shows that the variation in the ear morphology of the humans may be associated with a gene known as ectodysplasin A receptor (EDAR) gene. This is a key regulator gene of the embryonic skin appendage development. Some characters found associated with T-box protein 15 (TBX15) gene. Worldwide genetic studies related to the variations in ear morphology should be conducted in different population groups so that knowledge of their associated gene may be enhanced in order to further use the genetic technology of this trait in family linkage and human identification.