Thought provoking post, darklord.
I see it has produced some interesting dialogue. Like any other forms of aggression, rape can easily be assumed to have been around since the dawn of homo sapiens. The basic nature of humans has never changed, only time and societal customs. True to most of the answers posted, it is easy to conclude that in the time of "cave-men" rape was as much a means of procreation, as sexual desire and dominance. Although the majority of rape victims are female, (men are simply stronger than women). Non-incarcerated heterosexual rape of men on men is incredibly unreported. When it is reported, the victims are most often male children. In the crime of women raping men, it was found to happen most to men who are incarcerated. Coercive particpiation was achieved by threat or promise of preferential treatment.
Although rape is mentioned in the bible and other ancient texts, the etymology of the word as sexual violence in Western culture has been traced back to the 13th century Latin. By the 14th and 15th century, a particular rape that was recognized as violence against a woman in her own right was the rape of the noblewoman Lucretia and was a catalyst for the overthrow of the Roman Kingdom by the Roman Republic, which spawned the rise of emperors beginning with Julius Cesar. This rape was referred in stories of Shakespeare, Geoffrey Chaucer, and Thomas Heywood. A famous book of Western literature written in the 18th century in which the crime of rape was described as committed against the victim herself is by the novel Tess of the D'Urbervilles by Thoms Hardy. Botticelli, Rembrandt, Dürer, and Artemisia Gentileschi, to name just a few, have famous paintings in which it is the woman who is clearly violated in her own right. Although, as mentioned in previous posts, in general women and children were considered the property of their fathers and husbands until the early 20th century, when women were allowed to own property, to be the direct recipients of inheritance and off course the right to vote.
The question regarding why are younger women raped in greater numbers then older goes back to sexual desirability and the idea that younger are more readily able to reproduce. A common male fantasy often includeds impregnation of his victim. This adds additional forms of sexual dominance and humiliation.
I am not able to list the sources for the above conclusions due to lack of space.
I look forward to stumbling upon other posts of your, darklord.