First Rites are a rite of passage in most Cro-Magnon cultures, in which adolescent girls are ritually deflowered. After this, they are considered women and are allowed full status as adult members of their tribe, including being allowed to take a mate. This comes from a shared cultural value that young people must be taught about "The Mother's Gift of Pleasure", or sex. It usually involves pairing a young woman with an experienced older man so that she can be "opened" and gently introduced the Gift of Pleasure. Most girls have First Rites shortly after they have begun menstruating, meaning that the majority of girls having First Rites are between the ages of twelve and sixteen. The Rites can also be experienced by older girls or young women - for example, Ayla has a less formal version of First Rites with Jondalar at the age of seventeen, having never experienced the Gift of Pleasure (her only previous sexual encounters were being raped by Broud).
It is generally believed that girls cannot become pregnant until they've had First Rites; since people at this time have no idea that intercourse leads to conception, they believe that opening up a young woman shortly after starting her "moon times" will allow her to take in the spirit of a man and become pregnant. Merely not being a virgin any longer does not necessarily equate to having gone through First Rites. Girls who lose their virginity before First Rites are still required to have them, as only girls who have their Rites are considered full women and allowed the status and privileges that come with it. One example of this would be a pregnant Zelandonii girl who did not wait, but was still required to have First Rites so she could mate the father of her unborn child. Girls who have been sexually assaulted are also not considered as having had Rites, such as in the case of Ayla and a Losadunai girl, both of whom were raped before First Rites. This is probably because rape is viewed as being a serious taboo by most Cro-Magnon, a violation of a person's rights and perverse affront to the Mother's Gift. First Rites are intended to 'open' a girl and introduce her to the Gift of Pleasure; therefore sexual assault does not count.
Amongst the Zelandonii, at the least, girls who "cheat" by not waiting until First Rites to have sex is viewed as taboo, though girls are not seriously punished for this. However, they are generally looked down upon and viewed as lacking in self-control. Often, another adult will be present at First Rites to ensure the ritual is completed and that the girl is not harmed or made uncomfortable. It is considered a great honour for a man to be chosen for First Rites; men who are repeatedly chosen, such as Jondalar, as considered particularly attractive and honored. It is considered taboo for men who are biologically related to a girl to deflower her; as a result, the shamans of a culture must be careful in choosing a man who is not related to them. Even viewing a girl as being a relative can be considered taboo - Jondalar refuses to deflower a Mamutoi girl, Latie, on the grounds that he views her as a younger sister. Amongst the Zelandonii, it is considered improper for a woman to try and pursue a man who deflowered her at least a year, according to tradition.