Mutual masturbation, mutual manual stimulation of the genitals between partners, can be a substitute for sexual penetration. Starting with erotic stories and woodblock prints from before the 20th century, Japanese pornography evolved into distinct subcategories with the media that in addition of pornographic videos and magazines featuring live actors, there is exist categories of pornographic manga , pornographic computer games , and pornographic anime . Hardcore pornography is pornography that depicts penetration or extreme fetish acts, big tit milf or both. Evolutionary psychologists suggest that rounded buttocks may have evolved to be desirable trait because they provide a visual indication of the woman youth and fertility. This type of pornography is almost exclusively hentai, as true hermaphroditic humans are not fertile and are not usually found in nature. Internationally, hentai is a catch-all term to describe videos porno gay a genre of anime and manga pornography. When the interest in a particular subject is obsessive, the behavior may be described as stalking. Men may also rub or massage the glans, the rim of the glans, and the frenular delta. In the fetish cuckolding subculture, it is most common for the female to take on the sexually dominant role and the male the submissive role, however, female subs, sometimes referred to as cuckqueans, also exist. Both sexes sometimes apply lubricating substances to intensify sensation. The term BDSM dates back to 1969; however, the origin of the term BDSM is unclear and is believed to have been formed either from joining the term B&D with S&M , or as a compound initialism from B&D, D&S , and S&M. The hentai porn other person may do the same during or after. Irrespective of the legal or social view of pornography, it has been used in a number of contexts. Macrophilia is a fascination with or a sexual fantasy involving giants, more commonly expressed as giantesses . Bondage/BDSM Bondage pornography features performers tied up or constrained in various ways. Though there have been numerous gang bang pornographic films since the 1980s, they usually involved no more than half a dozen to a dozen men.