Infanticide (the killing of infants of the same but unrelated species) can be seen throughout the animal kingdom, from lions to birds , but it has been observed that primates practice this phenomenon more than any other order. It has been observed in several species ranging from chimpanzees to macaques, but it appears that a large proportion of infanticides have one thing in common:; they are followed by a copulation of the attacker with the widowed mother. Some observations use game theory and explain these actions in terms of risks and rewards. My hypothesis is that this leads to better fitness and reproductive success in males who commit infanticide compared to those who do not. in other groups of chimpanzees [1]. This has been observed several times and is often believed to involve cannibalization of the infant [1]. It has also been observed that females whose child has been killed occasionally join the group that killed it and allow themselves to copulate with it [1]. Although, admittedly, according to the article, they were not absolutely sure that every woman whose child was killed belonged to an out-group [1]. This infanticide appears to be more the result of wars and conflicts, rather than greater adaptation to individual chimpanzees, but it sometimes leads to the appearance of a new female in the group [1]. This both reduces the reproductive success of their rivals, allowing them to exploit their rivals in fewer numbers and increase their territory. One thing that sets chimpanzees apart from the other primates that are going to be mentioned is the...... middle of paper......thansiama. 2013 Infanticide in captive stub-tailed macaques (Macaca arctoides) is consistent with the sexual selection hypothesis. Current Science 104, 1081-10835.) Fruteau C, Range F, Noe R. 2009 Risk of infanticide and infant defense in free-ranging multi-male sooty mangabeys, Cercocebus atys. Behavioral Processes 83, 113-1186.) Zhao Q, Borries C, Pan W. 2011 Male takeover, infanticide, and female countertactics in white-headed leaf monkeys (Trachypithecus leucocephalus). Behavioral Ecology Sociobiology 65, 1535-15477.) Beaudrot LH, Kahlenberg SM, Marshall AJ. 2009 Why male orangutans don't kill infants. Behavioral Ecology and Sociobiology 63, 1549-15628.) Opie C, Atkinson QD, Dunbar RIM, Shultz S. 2013 Male infanticide leads to social monogamy in primates. Proceedings of the National Academy of Sciences of the United States of America 110, 13328-13332