The document summarizes the current scientific research into the biological factors that influence sexual orientation. It notes that biology has begun to study what causes homosexuality and has provided some early answers, though the findings are still tentative. It also acknowledges that researching sexuality and the brain is challenging given our limited understanding of neurobiology. Some fear the quest to find biological explanations could lead to hype or be an intellectual dead end. The document concludes by saying the topic is politically charged, which has led to professional rivalries among researchers, some of whom have personal motivations as they themselves are gay.