According to the evolution of life, mammals are the most advanced creatures. Human beings are the most advanced creatures among mammals. Human beings are being different from other creatures by their advanced human features. Paternity is one of most advanced human features that we can recognize. Unlike in other animals paternity is an essential thing of human society.
Most of animals have a special period of reproduction. Mating male and female creatures and breeding are happening within this particular period. Female creature bears the kids and nurtures until the kids are grown enough to procure their requirements for the persistence. In most of animals this thing is common and no need of male creatures for kids to grow up. Because of the psychological factor of sex in most of animals is not complex. Growing physically and become sexually matured are just enough for completing their life cycle. But in human beings, the psychological factor of sex is a complex. Mothers cannot develop the sexuality of boys psychologically without fathers. Because of masculine gender is a paternal inheritance. Psychological masculinity of males is heavily depending on the masculine gender specifications of their fathers. According to the evolution of human beings, paternity is a feature which developed by the nature just because of the requirement of developing entire male sexuality. We cannot simply ignore this fact when we are talking about the evolution of human sexuality. We have to approach a new way of thinking for understanding the truth about human sexuality.