Going back at least as far as the Christy twins in the 1970s, depictions of incest mature milfs and particularly incest between twins has been a feature of gay pornography. In September 2003 the BBC reported on the new dogging craze. Spanking or whipping pornography involves spanking or whipping, generally of the buttocks, with the hand or with other objects such as belts, switches, paddles, brushes, or gaysex whips. Group sex is sexual behavior involving more than two participants. It is suggested that much of the obscurity and the uncertainties about female ejaculation are related to mixing up these two phenomena. The buttocks in human females thus contain more adipose tissue than in males, especially after puberty. The nipples are erogenous zones, and vigorous stimulation of them during masturbation usually causes the penis to become erect more quickly than it would otherwise. Enema pornography involves adults given enemas to others, often fake. Although pornography has usually focused on heterosexuality, due to the prevalence of the heterosexual orientation, explicit gay material has a long history as well, which reaches back to Greek antiquity, if not to prehistory. Hentai is the various forms of Japanese pornography, including H-manga, H-anime, and H-computer games. By Japanese law, the genitals of actors and actresses must be censored and up the mid-1990 so was the depiction of pubic hair. Matsuo used amateur actresses in his videos, and he usually traveled to their hometowns for the filming. This category also includes pornographic home movies. It may be regarded as taboo or unnatural, and is a criminal offense in some countries, punishable by corporal or capital punishment; by contrast, people also regard anal sex as a natural anime hentai and valid form of sexual activity that may be as equally fulfilling as any other desired sexual expression. This style of filming is in contrast to having a separate, third-person camera crew filming all the action. Mammary intercourse is said by Alex Comfort to produce mutual orgasm in women with sensitive breasts , and it was one of the nine substitute exercises for penetrative sexual activities, as detailed in the Paradis Charnels of 1903.
