Kin selection is an evolutionary strategy that places the reproductive success of a relative above the actor (Hamilton, 1964). Even if an actor cannot pass on his genes, whether because he is infertile or because he cannot find a mate, if he helps a sibling or parent by raising other children, he ensures that his 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. In some primates, such as tamarins, they tend to have twins with each birth cycle. Caring for twins can be really difficult, so adult tamarins rely on older offspring or other close relatives to help raise new sets of offspring. When primates mate, only the mother can be sure that she is the mother. The father, however, cannot be sure whether he is the father or not. Many primates, such as chimpanzees, practice infanticide within groups so they can mate with the females of that group. To ensure this doesn't happen, females will mate with multiple males, ensuring that males or the male within the group does not commit infanticide. This act confuses the male, making him doubt whether that offspring is his or not, so instead of risking his physical form, he will protect the offspring and the female as if he knew for sure that the offspring was his. But how can the male know with certainty whether that offspring belongs to him or not? Some researchers have discussed and tested kin recognition theory (Blaustein, 1983). Recognition of kin is one way that males can be sure which offspring are theirs. When recognizing relatives, many people believe that odors that come from a specific parent are... middle of the paper... The experiments reported in this article show that, while many humans may not be able to distinguish others at times, they can actually do this through simple cues and comparisons with themselves. The same can be said for animals. While not all animals avoid incest, some may speculate that those who resemble the actor(s) are and may be related to them, so should not breed with them. This hypothesis tells researchers that although it may not seem like family groups can distinguish themselves from each other due to certain acts of the group, this is actually possible. Fathers are able to know what their offspring are, thus ensuring an investment in that offspring, so that the offspring can survive to reproductive age. Kinship recognition can also be seen as a mechanism that not only ensures investment in the right offspring, but also an investment in the relative reproductive success of relatives (Blaustein, 1983).