What are the characteristics of boys and girls? Having a boy or girl is a very mysterious topic that is of great concern to many people. According to scientific research, human beings do have some innate characteristics when they are born boys and girls. Next, we will discuss the characteristics of boys and girls from four aspects: gender genes, body shape, personality characteristics and physiological life cycle. The first aspect of gender genes is gender genes. Human gender is controlled by two genes: X and Y.