AMERICAN JOURNAL OF SCIENTIFIC AND INDUSTRIAL RESEARCH © 2011, Science Huβ, http://www.scihub.org/AJSIR ISSN: 2153-649X doi:10.5251/ajsir.2011.2.6.871.876 Sexual dimorphism in cranial dimensions among three ethnic groups of North-Eastern Nigeria M. B. Maina, O. Mahdi and G.D. Kalayi Department Of Human Anatomy, College of Medical Sciences, Gombe State University, Tudun Wada Quarters, Gombe ABSTRACT The study of sexual dimorphism is important clinically, in forensic anthropology and craniometry. Therefore this study was design to identify the sexual dimorphisms in cranial dimensions among three ethnic groups of North-Eastern Nigeria and to compare this study with other similar studies. Cranial length, width, height and circumference in Fulani, Tangale and Tera ethnic groups were linearly measured in a total of 300 (150 males and 150 females) 18-40 years old subjects. The result showed that all cranial dimensions among the three ethnic groups are higher in males than in females, except cranial width which is higher in Fulani (138.7±10.4mm) than in their male counterparts (136.8±10.6mm). The most prominent difference in cranial dimensions between the males and females among the three ethnic groups is in cranial length where males values are significantly higher than females values (p<0.005). Interestingly, the values of cranial width were found to fluctuate between males and females. Therefore, the findings from this study revealed that sexual dimorphism exists between Fulanis, Tangales and Teras of Gombe and based on comparison with other studies we postulate that the effect of gender on cranial width is not consistent. Furthermore, the study confirms the effect of ethnic and geographic difference on cranial dimensions. Keywords: North-Eastern Nigeria, Ethnicity, Sexual dimorphism, cranial dimensions. INTRODUCTION Sexual dimorphism is the difference best observed based on phenotype between males and females of the same species. Study of sexual dimorphism is important clinically, in forensic anthropology as well as in craniometry. Craniometry is a branch of anthropometry through which cranial dimensions can be estimated. The most important of craniometric dimension are height and width of head that they used in cephalic index determination (Vojdani et al. 2009). Cranial dimensions are not stable during earlier years of life due to further development such as the closure of anterior and posterior fontanel, but are stable over time (between 20-80 years) (Cotton et al., 2005). In early life there is little difference between male and female skulls, in adulthood male skulls tend to be larger and more robust than female skulls, which are lighter and smaller, with a cranial capacity about 10 percent less than that of the male (Gray’s Anatomy 1935). A well-marked male or female skull can easily be recognized as such, but in some cases the respective characteristics are so indistinct that the determination of the sex may be difficult or impossible. Several studies have documented various sexual dimorphisms related to craniometry (Maina et al. 2011; Raji et al. 2010; Vojdani et al. 2010; Golalipour et al. 2005). Furthermore, ethnic, ecological, biological, geographical, racial, age and nutritional factors also affect cranial dimensions (Golalipour et al., 2003, Rajlakshmi et al., 2001, Radovic et al., 2000, Tuli et al. 1995 and Okupe et al., 1984) making it difficult to identify the sex of a skull without knowledge of the population from which it came. Cranial dimensions of newborns are not stable because cranial length, height and width increase as growth progress (Trenouth, 1991), hence, this study was undertaken in adult males and females Fulani, Tangale and Tera to observe sexual dimorphism in their cranial dimensions and to compare this study with other similar studies. MATERIALS AND METHODS Subjects: This study was conducted on 18-40 years normal randomly selected Fulanis, Tangales and Teras of Gombe state region of North-Eastern Nigeria origin, from March to June 2011. Gombe State lies in the centre of the North-East geopolitical zone of Nigeria. It shares a common boundary with all the other states in the zone, namely, Adamawa,