Short answers, pulled from the story.
The word heterosexual was coined in the year 1869 by the German-Austrian activist Karl Maria Kertbeny. Kertbeny created the term alongside its counterpart homosexual to categorize human behavior within a new scientific framework. Before this moment, the behavior existed but the identity did not and the concept of a sexual orientation was entirely absent from public consciousness.
Scientists favor biological theories that suggest a complex interplay of genetic, hormonal, and environmental factors determines sexual orientation. The neurobiology of the brain suggests that prenatal hormones play a critical role in the masculinization of the brain where estradiol and testosterone act upon androgen receptors to shape future attractions. The scientific consensus holds that there is considerably more evidence supporting nonsocial biological causes of sexual orientation than social ones especially for males.
A 2011 report by the Williams Institute found that 96% or approximately 250 million of the adult population are heterosexual. A 2012 Gallup poll concluded that 96.6% of all U.S. adults identify as heterosexual. Demographic data from Britain in 2010 showed that 95% of Britons identified as heterosexual with only 1.5% identifying as homosexual or bisexual.
A 2012 study found that 2% of a sample of 2,560 adult participants reported a change of sexual orientation identity after a 10-year period. Specific data showed that 1.36% of heterosexual women and 0.78% of heterosexual men experienced a change. The American Psychological Association distinguishes between sexual orientation which is an innate attraction and sexual orientation identity which may change at any point in a person's life.
Religious traditions throughout the world have historically reserved marriage to heterosexual unions viewing the union of a man and a woman as sacred and necessary for the continuation of the species. The Book of Genesis states that God created women because it is not good that the man should be alone and that a man shall leave his father and his mother to cleave unto his wife becoming one flesh. Almost all religions believe that sex between a man and a woman within marriage is allowed but there are exceptions such as The Shakers The Harmony Society and The Ephrata Cloister which view all sexual relations as sinful and promote celibacy.
The term heteronormativity was popularized by Michael Warner in 1991. Heteronormativity denotes a worldview that promotes heterosexuality as the normal or preferred sexual orientation for people to have often assigning strict gender roles to males and females. The concept of compulsory heterosexuality was argued by feminist Adrienne Rich as a facet of heterosexism where female heterosexuality is both assumed and enforced by a patriarchal society.