As a child that grew up in the middle of other countries' wars, Nagato did not like killing and was horrified by his early acts of violence against those who had harmed his friends and family. He supported Yahiko's Akatsuki because it wanted to end the wars and deaths that he hated so much. After Yahiko's death, Nagato compromised his aversion to killing to a large extent, believing the deaths of specific individuals or even hundreds at a time could be justified if it served a greater and/or long-term purpose. But Nagato remains very clear in this distinction, as he shows mercy to those willing to cooperate with him and discourages others from defying him because it will only force him to strike them down. Minato Namikaze believes that, at some point along the way, Nagato's views were corrupted and subsequently manipulated by Tobi. 
The general body shapes of female and male bodies both have significant social and cultural symbolism. Physical attractiveness is closely associated with traits that are considered typical of either sex. The body mass index ( BMI ), waist-to-hip ratio, and especially waist-to-chest ratio in men have been shown in studies to rank as overall more desirable to women. Wide shoulders, a muscular upper body and well-developed upper-arm muscles are all traits closely associated with masculinity , similarly to other specifics of the male sex, like beards . These traits are seen more sexually attractive to women and also associated with higher intelligence, good leadership qualities and better health. 
Most mammals , including humans , are genetically determined as such by the XY sex-determination system where males have an XY (as opposed to XX) sex chromosome . It is also possible in a variety of species, including humans, to be XXY or have other intersex / hermaphroditic qualities, though one would still be considered genotypically (if not necessarily phenotypically) male so long as one has a Y-chromosome. During reproduction , a male can give either an X sperm or a Y sperm, while a female can only give an X egg. A Y sperm and an X egg produce a male, while an X sperm and an X egg produce a female .