section_path: Causes/Biology
section_name: Biology
paragraph_text: Biology
  
  Research has identified several biological factors which may be related to the development of sexual orientation, including genes, prenatal hormones, and brain structure. No single controlling cause has been identified, and research is continuing in this area.
  
  Although researchers generally believe that sexual orientation is not determined by any one factor but by a combination of genetic, hormonal, and environmental influences, with biological factors involving a complex interplay of genetic factors and the early uterine environment, they favor biological models for the cause. There is considerably more evidence supporting nonsocial, biological causes of sexual orientation than social ones, especially for males. Scientists do not believe that sexual orientation is a choice, and some of them believe that it is established at conception. Current scientific investigation usually seeks to find biological explanations for the adoption of a particular sexual orientation. Scientific studies have found a number of statistical biological differences between gay people and heterosexuals, which may result from the same underlying cause as sexual orientation itself.