Spanking can be administered in a number of spanking positions. Mutual masturbation, mutual manual stimulation of the genitals between partners, gaysex can be a substitute for sexual penetration. A study of the condom usage habits of New Zealand sex workers said that they offered various safe sex alternatives to vaginal sex to clients who refused to wear a condom. Reality and voyeur pornography, animated videos, and legally prohibited acts also influence the classification of pornography. Sometimes one or more fingers may be inserted into the vagina to stroke its frontal wall where the G-spot may be located. Works in this genre may be considered adult for any number of reasons. Sub-genres can also be classified into the characteristics of the performers or the type of sexual activity on which it concentrates, and not necessarily on the market to which each sub-genre appeals. In humans, females generally have more round and voluptuous buttocks, caused by estrogen that encourages the body to store fat in the buttocks, hips, and thighs. Irrespective of the legal or social view of pornography, it has been used in a number of contexts. It is typically animated pornography, as the legal age to be featured in a pornographic film in Japan is 18. Women who perform in lesbian pornography often do not consider themselves lesbian or bisexual. However, various groups within society considered such depictions immoral, labelling them pornographic, and attempting to have them suppressed under obscenity laws, with varying degrees of success. Yuri : Featuring two grown adult women in a homosexual/lesbian relationship. This is commonly called big tit milf double vaginal penetration or double stuffing. Felching is a sexual practice involving the act of orally sucking semen out of the vagina or anus of one partner. Bestiality is illegal in many countries. For example, in Australia it is rated Refused Classification . Biological anthropologist Helen B. What seems clear from 3d hentai the historical record is that much of the lesbian material in pornographic texts was intended for a male readership.