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. Unlike many other animals, humans need their fathers well beyond the act that leads to conception, researchers are coming to realize. Paternal prep school There is plenty of time for this emotional hand-off. While other primate babies can fend for themselves in roughly a decade, human childhood stretches 18 to 20 years, said David Geary of the University of Missouri and author of "Male, Female: Evolution of Human Sex Differences" (American Psychological Association, 1998). Also, anthropologists speculate that the relative helplessness of human children has made multiple caregivers a vital necessity — that encourages bringing dad into the picture. Even today, in both traditional and industrialized communities, a father's presence correlates with improved health and decreased child mortality, Geary said. Evolutionarily speaking, he added, the kid-phase probably lengthened as dads got more involved. With an extra person dedicated to caring for them, kids have no need to rush towards adulthood. Perhaps out of worry for their kids' future financial security, dads across human cultures mostly focus on preparing children to compete within society. They give advice, encourage academic success and stress achievement, Geary said. But it is not all lesson plans and lectures. Kids also learn from fathers during a unique form of papa play. Unlike mothers, fathers tend to roughhouse with their children. "They rile them up, almost to the point that they are going to snap, and then calm them down," Geary said. This pattern teaches kids to control their emotions — a trait that garners them popularity among superiors and peers, he said. Parenting for the grandkids Good fathers are rewarded with quality family relationships across the board, Geary said. When children have warm relationships with their father, as well as calm home lives, they tend to sexually mature later. Their bodies intuit they are safe and time is taken perfecting social skills before entering the real world, Geary said. The extra practice gives children a competitive edge. As adults, they are more likely to form secure relationships, achieve stable social standing and become able parents. In this sense, a father who takes care of his children also gives his grandchildren a leg up. Not that involved dads must wait to be grandpas to reap rewards from pitching in with childcare. In addition to experiencing the tenderness of the father-child bond, many dads gain a feeling of camaraderie by providing support for mom. Also, the more help a mother receives after giving birth, the faster she becomes fertile again. Being raised by more than one person also enhances social skills, theorizes anthropologist Sarah Hrdy, author of "Mothers and Others" (Belknap Press, 2009). Children not only grow up more emotionally secure, they are better at taking another's perspective — a skill critical to our socially-reliant species. In traditional communities, especially during infancy, extra caregivers are usually female kin, such as grandmothers and aunts, Hrdy writes. But in nuclear families, fathers play this role. When father-child relations are strained or chaotic, the insecurity can translate biologically as a message to grow up fast, Geary said. There is an unconscious sense that "if you are going to reproduce at all, you better start early," he said. As a result, girls reach menarche sooner and form clingy relationships, while boys become aggressive and sexually exploitive. This rarely bodes well for the next generation. Biological roots of paternalism The emotional contribution of dads might have some biological roots. Despite conventional wisdom, men experience biological changes during a pregnancy, albeit not as extensively as women do. Men who are emotionally close to — and usually cohabiting with — a pregnant woman, go through their own hormonal surges, especially just before and after birth, said David Bjorklund of Florida Atlantic University. For example, a new father has elevated levels of the hormone prolactin — usually associated with lactation in women — that trigger his nurturing instinct. This may be evolution's way of ensuring more constant care for a baby that is more dependent and demanding than any other newborn in the animal kingdom.

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