Biological variations are the prime important properties of evolution which through the process of selection shapes the animal body which are generally being considered as signatures for understanding the evolution. Like other organs and parts of animal body, hair has also a range of diversity and the microscopic details of hair strands offer certain definite and variable features as well. These are found to be useful for the purpose of identification. This book contains a doctoral work on some intricate facts of Primates head hair for the partial understanding of species specific variation and Evolution. The present study attempted to understand the variation of some histomorphological and qualitative variables of hair within different species and between different primates Genus and to identify the sexual dimorphisms within different Species. Since Sexual Dimorphism is one of the major features of evolution, sex differences in terms of different histomorphological and quantitative variables might be of basic interest for partial understanding of the evolutionary process.