ATHEISTS: If ity is normal then why have generations of people considered it sinful?

Think of it.............if it was natural and i do know that it happens in the animal kingdom a lot and has been happening for centuries but you have to consider that animals don't have critical thinking ability like us humans and because of that we humans are different from animals........now despite having critical thinking ability uality has been a taboo for centuries................hmmmm something to think about......so its inherently sinful.......as it is accounts for a majority in the spread of HIV......a sign from God that its sinful?