I heard a theory that gay behavior is actually caused by intestinal parasites and it seems plausible enough to warrant scientific investigation. Liver flukes, cordyceps, and toxoplasma gondii are already known to cause complex behavior changes in the host to perpetuate the life cycle of the parasite - so something that causes humans to be obsessed with feces to consume and spread parasite eggs is not an unreasonable hypothesis.

I heard a theory that gay behavior is actually caused by intestinal parasites and it seems plausible enough to warrant scientific investigation.