Final answer:
The likelihood of identical twins sharing sexual orientation more than fraternal twins suggests a genetic component. While genetic factors play a role, there's no consensus on the definitive causes of sexual orientation.
Step-by-step explanation:
The fact that identical twins are more likely to share sexual orientation than fraternal twins suggests that sexual orientation is at least partly genetic. Studies have shown gene-level contributions to sexual orientation, with some research estimating that genes account for at least half of the variability seen in human sexual orientation. Additionally, differences in brain structure, function, and even basic body structure among individuals with different sexual orientations also suggest a biological component. However, it is important to note that there is no scientific consensus on the exact reasons for an individual's sexual orientation, and various genetic, hormonal, developmental, social, and cultural factors are all thought to play roles.