Sexual differentiation in humans Sexual differentiation in humans Sexual differentiation in humans is the process of development of sex differences in humans. It is defined as the development of phenotypic structures consequent to the action of hormones produced following gonadal determination. Sexual differentiation includes development of different genitalia and the internal genital tracts, breasts, body hair, and plays a role in gender identification. The development of sexual differences begins with the XY sex-determination system that is present in humans, and complex mechanisms are responsible for the development of the phenotypic differences between male and female humans from an undifferentiated zygote. Females have two X
My Teacher Is an Alien as a means of communication among other aliens in the galaxy who are trying to decide what they want to do with humans. Susan, the hero of the previous story, tries to save Duncan when Kreeblim is out of her house, however the two of them do not get out of the house in time. At the end of the book, Peter (with enhanced eyesight and no need of glasses) and Broxholm return, and Duncan and Susan decide to help Peter prove to the Interplanetary Council, the ruling aliens of the galaxy, that the human race is worth saving. Peter