may be a counterstrategy to infanticide because it confuses paternity. If male bonobos cannot distinguish their own offspring from others, the incentive for infanticide essentially disappears. This is a reproductive strategy that seems specific to bonobos; infanticide is observed in all other great apes except orangutans. It is unknown how the bonobo avoids simian immunodeficiency virus (SIV) and its effects. Peacefulness Observations in the wild indicate that the males among the related common chimpanzee communities are hostile to males from outside the community. Parties of males 'patrol' for the neighboring males that might be traveling alone, and attack those single males, often killing them. This does not appear to be the behavior of bonobo males or females, which seem to prefer sexual contact over violent confrontation with outsiders. While bonobos are more peaceful than chimpanzees, it is not true that they are unaggressive. In the wild, among males, bonobos are half as aggressive as chimpanzees, while female bonobos are more aggressive than female chimpanzees. Both bonobos and chimpanzees exhibit physical aggression more than 100 times as often as humans do. Although referred to as peaceful, bonobo aggression is not restricted to each other, and humans have also been attacked by bonobos, and suffered serious, albeit non-fatal, injuries. Bonobos are far less violent than chimpanzees, though, as lethal aggression is essentially nonexistent among bonobos while being not infrequent among chimpanzees. It has been hypothesized that bonobos are able to live a more peaceful lifestyle in part because of an abundance of nutritious vegetation in their natural habitat, allowing them to travel and forage in large parties. Recent studies show that there are significant brain differences between bonobos and chimpanzees. Bonobos have more grey matter volume in the right anterior insula, right dorsal amygdala, hypothalamus, and right dorsomedial prefrontal cortex, all of which are regions assumed to be vital for feeling empathy, sensing distress in others and feeling anxiety. They also have a thick connection between the amygdala, an important area that can spark aggression, and the ventral anterior cingulate cortex, which has been shown to help control impulses in humans. This thicker connection may make them better at regulating their emotional impulses and behavior. Bonobo society is dominated by females, and severing the lifelong alliance between mothers and their male offspring may make them vulnerable to female aggression. De Waal has warned of the danger of romanticizing bonobos: "All animals are