Quote from OPTIONAL777:
"The purpose of sex is reproduction and biological evolution of our species."
Then every time anyone masturbates is unnatural, every time a woman or man who is sterile has sex is unnatural, old women who have are too old biologically to have children when they have sex is unnatural, any man who has a vasectomy having sex is unnatural, any woman who has had a hysterectomy when she has sex is unnatural...
No, sex has a purpose beyond procreation...
Animals in the wild have sex with other members of the same sex...
Are you really as dense as your statement above?
The forces of evolution did not give us a penis so that we could jerk off. (That may have been the case in your situation, I don't know.)
We were given a penis so that we could copulate with a female and evolve our species.
Try it sometime and I think you'll see the point.