Final answer:
Research supports the idea that sexual orientation has a genetic and biological basis, with gene studies and observed differences in brain and physical structures lending evidence to this conclusion, while cultural factors shape attitudes and experiences rather than the causes of orientation itself.
Step-by-step explanation:
The research findings reported in the chapter support the view that sexual orientation is linked to "natural" causes, specifically to genetic predisposition.
Genetic and biological mechanisms have been proposed as underlying causes of sexual orientation, with research evidence indicating a biological component. Studies over 25 years have shown contributions at the gene-level to sexual orientation, suggesting that to a meaningful extent, orientations are something with which individuals are born. Additionally, differences in brain structure and function as well as basic body structure have been observed among people of varying sexual orientations.
Sociocultural factors do influence attitudes and discrimination faced by the LGBTQ community, but they are not directly linked to the causes of sexual orientation itself. Importantly, familial and socialization differences have not been shown to cause differences in orientation. Therefore, a) Genetic predisposition is the factor that supports a linkage to natural causes in the context of the given options.