You can get or transmit HIV only through specific activities. Most commonly, people get or transmit HIV through sexual behaviors and needle or syringe use. Only certain body fluids—blood, semen cum , pre-seminal fluid pre-cum , rectal fluids, vaginal fluids, and breast milk—from a person who has HIV can transmit HIV. These fluids must come in contact with a mucous membrane or damaged tissue or be directly injected into the bloodstream from a needle or syringe for transmission to occur.
Researchers studying fruit flies found their progeny's size could be influenced by the length of a previous mate. This may be because chemicals in the original male's seminal fluid can have a lingering effect, and scientists have even suggested that something similar could occur in humans. The theory is known as 'telegony' and was first proposed by Aristotle in ancient Greece. It was one of the reasons kings were banned from marrying divorcees. The theory was discredited thanks to the advent of genetics. But now, writing in the journal Ecology and Evolution, scientists have suggested flings can influence the offspring of future mates.