Parent selection is an evolutionary strategy that places the reproductive success of a parent above the actor (Hamilton, 1964). Even if an actor cannot pass on his genes, whether because he is sterile or because he cannot find a mate, if he helps a sibling or parent by raising other offspring, he is careful to that its genes are passed on to the next generation. . When an actor helps raise siblings or cousins, those siblings and cousins ​​have at least 25% of the actor's genes that they can pass on. Some primates, such as tamarins, tend to have twins in each birth cycle. Caring for twins can be very difficult, so adult tamarins rely on older offspring or other close relatives to help them raise the new offspring. When primates mate, only the mother can be sure that she is the mother. The father, however, cannot be sure if he is the father or not. Many primates, such as chimpanzees, engage in infanticide within groups in order to be able to breed with females in that group. To prevent this from happening, females will mate with multiple males, ensuring that males or males in the group will not commit infanticide. This act confuses the male, causing him to question whether or not these offspring belong to him. So instead of risking his fitness, he will protect the offspring and the female as if he knows for sure that the offspring are his. But how can the male know for sure whether this offspring belongs to him or not? Some researchers have discussed and experimented with parent recognition theory (Blaustein, 1983). Recognition of parents is a way for men to know with certainty who their offspring are. When recognizing a parent, many people believe that odors coming from a specific parent are...... middle of article...... the experiments presented in this article show that even if Many humans are not able to distinguish others at any given time, Sometimes they really can by simple cues and comparisons with themselves. The same can be said for animals. Although not all animals avoid incest, some may do so under the assumption that those who resemble the actor(s) are and can be related to them, and therefore should not breed with them. This hypothesis tells researchers that even if it appears that family groups cannot distinguish themselves, due to certain actions within the group, they actually can. Fathers are able to know what their offspring are, thus ensuring investment in those offspring, so that they can survive to reproductive age. Parental recognition can also be seen as a mechanism ensuring not only investment in good offspring, but also investment in the relative reproductive success of parents (Blaustein)., 1983).