If you want to fuck a girl in the ass - fuck her in the pussy.
There nerve endings that stimulate the prostate in the ass. These get stimulated in gay sex. But in women - those nerve endings are found in the vagina. This is where the 'G spot' is found in men and women.
So - as with gay sex - women will only be able to come from vaginal intercourse if she is submissive to the one doing the fucking. With the rise of feminism - and 'equality' - women are losing the ability to let themselves be dominated. Which will mean the dying out of orgasms from vaginal penetrations.
Clittoral orgasms should be fine (which are weaker - but much longer - than male orgasms by the way). But due to the psychological element. A women will only have a 'G spot' orgasm from a man who is dominating her. No 'nice guy' or sex toy will ever get her to achieve one.
Personally - I sense most men were fucked in the ass thousands of years ago as a way of keeping them submissive and in line. Alot like with prison rape today. The methods of discipline used in armies were pretty brutal back then.
And things like femdom are a hangover from those days. Since there will have being an evolutionary pressure - which meant the most successful armies were the ones who were most submissive to their commanders. Which will have led to an increase in pleasure due to anal sex passing through the generations. And such traits will have being passed down from the beta males of thousands of years ago to the beta males of today.
Sorry - for all the above. It is a bit gross. I am just trying to make make some guesses as to what went on in ancient history. Some of the most startling things about history are unknown to us today. Which can lead us to unknowingly perpetuating myths.
A recent example of this is the myth of the eight-hour sleep:
http://www.bbc.co.uk/news/magazine-16964783