This paper will discuss the roles of biological factors—nature—and environmental influences—nurture—on sexual differentiation and gender identity. The paper will also determine which has the greater influence on gender identity: nature or nurture. Lastly, the paper will discuss the current arguments about sexual identity and how evidence from biopsychology may help resolve the argument.

Biological Factors on Sexual Differentiation and Gender Identity
Gender identity is being either male or female. Gender identity is the element that helps make up an individual's sense of self. Before a baby is born their gender is form to either a boy or girl. There are 23 pairs of chromosomes in the human body and it is known that the ova and sperm cells contains part of that number (Rathus, Nevid, & Fichner-Rathus, 2011). When a sperm cell fertilizes an ovum, the zygote ends up having the whole 23 pairs of chromosomes, one is from the father and one is from the mother (Pinel, 2009). When a sperm fertilizes an egg, the development of the zygote in the male or female will depend on whether the sperm is carrying an X or Y sex chromosome (Pinel, 2009). Female ova contain only an X sex chromosome and needs the sperm to provide a Y sex chromosome, which develops a male and if it X sex chromosome the zygote will develop a female. In the case of hormones males and females have different levels of hormones. Hormones that influence an individual’s behavior can produce either masculine or feminine bodies (Pinel, 2009). Estrogens androgens, and progestins are several hormones in the body. The most common classes of gonadal hormones are androgens and estrogens. The gonads not only create sperm and egg cells, but they also produce and release steroid hormones. It is clear that the testes and ovaries produces the very same hormones. Androgens and estrogens are both the most common classes of gonadal hormones. Progestins is another class of gonadal hormones, which is released by the ovaries and testes. The Progesterone helps pregnancy in females and not men (Pinel, 2009). It has been assumed that androgens are male hormones and estrogens are female hormones, but the fact is that male and female hormones are not at the same level, but they do have the same hormones and do not perform the same function (Pinel, 2009). It is found that males and females at the fetal stage may have been in contact with estrogens, but it is known if males came more in contact with androgen at the fetal stage (Pinel, 2009). Studies have found that females who had an early exposure to male hormone have masculine behaviors. On the other hand, studies have also found that men with low testosterone levels have female behavior (Pinel, 2009). Overall, it is clear that hormones and behavior play a role an individual gender identity (Pinel, 2009).

Environmental Factors on Sexual Differentiation and Gender Identity
The environment such as the home is always the first place a child grows up and gets to learns about different things about themselves. The family is the first teacher in the child’s life that teaches the child everything that they need to know, which in the end can have an impact on his/her gender identity. For example, as soon as a baby is born the parents starts to treat the baby according to the gender and dress them either in boys or girls clothing (Rathus, Nevid, & Fichner-Rathus, 2011). As the baby grows up the parents starts playing different role in the child’s life, which influences their behavior. For example, boys are raised by their dad to become strong, whereas girls are raised by their mom to be soft and gentle. Overall, the family is the first environment where a child learns about the sense of self. In this case, parents play the most important role in the child’s gender identity. For example, if parent are always telling their female child that boys are better in sports than girls this may make the female child to feel that they are not good enough as a female and they may end up wanting to change their gender identity to a male. Outside the home also have influences on a child’s gender identity. Some influences outside the home that influences a child’s gender identity are school, television, music, and friends (Rathus, Nevid, & Fichner-Rathus, 2011). For example, when a child starts going to school they may want to try out what it feels like to have a relationship with the same sex because they had viewed it on the television this in the end influences their gender identity. Studies have also showed that parents who allow their children to cross-dress may encourage them to start dressing like the opposite sex. Other studies have also showed that parents who allow their male child to play with dolls will have feminine behavior and a female child who play with cars will have masculine behavior. Overall, environmental factors play a role in sexual differentiation and gender identity. It is clear that when a child is growing up it is important that they feel comfortable with their own gender identity because if they don’t this can cause them to stray away from their own true gender identity to the same gender (Rathus, Nevid, & Fichner-Rathus, 2011).