Final answer:
A homosexual orientation is strongly influenced by genetics and biology, supported by extensive research indicating gene-level contributions and observed differences in brain and body structure.
Step-by-step explanation:
A homosexual orientation appears to be the result of genetics and biology playing a dominant role. Scientific studies have revealed that there is significant evidence to suggest that sexual orientation has an underlying biological component. Several research works over the past several decades have demonstrated gene-level contributions to sexual orientation, and numerous studies report differences in brain structure and function among those with different sexual orientations. Furthermore, there have been observed differences in basic body structure and function that correlate with orientation. While there is no scientific consensus that links sexual orientation to one singular factor, the evidence supports the idea that genetics and biology are a significant part of the equation.