Scientists, philosophers and theologians have argued humankind's difference with animals for centuries. The arrival of the Darwinian theory of evolution changed part of this, with more people believing now that we have indeed descended from animals, but with more developed physiological faculties as evolved for survival. Recent studies suggest, though, that humans have been hardwired to be similar to their ancestors in more ways than appearances.

Emory University primatologist Frans de Waal suggests that we humans may be exhibiting behavior that we unconsciously follow from our ancestral animal instincts. He compares upset human behavior such as hurling a chair upon hearing unfavorable news, or being hostile to rivals, to behavior exhibited by chimpanzees. 

Biologist Emily DuVal, meanwhile, thinks that our "wingman" or "wingwoman" behavior - when we help out a friend to impress a potential mate - could be likened to the behavior of lance-tailed manakins in Panama. Some males of this species of birds will perform a dance to impress a watching female bird, and attract her to the alpha male manakin.

In another study made by avian ecologist Jeffrey Hoover, he compares the behavior of cowbirds to the behavior of mafia gangsters. The said birds parasite the nests of smaller songbirds and will damage the eggs of birds that resist. All of these studies suggest that human behavior may be more instinct-based than we previously thought it to be.

So cut yourself some slack when you start craving for dog food. You may only be taking hold of an animal instinct inside you. Mmm, yummy dogfood...