Some 95 percent of male mammals have little to no interaction with their children. Homo sapiens are one of the most notable exceptions, leading some scientists to think fatherhood is an important part of what makes us human.

Most theories for the family involvement of fathers invoke the familiar "Man the Hunter" characterization, in which dad protects and provides for his young.

While fathers do play key roles in securing the physical health of their children, they also can be important for the optimum development of psychological and emotional traits considered to be primarily human, such as empathy, emotional control and the ability to navigate complex social relationships.

Kids also learn from fathers during a unique form of papa play. Unlike mothers, fathers tend to roughhouse with their children.