Research by biologists on social organization in animal groups led to the frequent observation that some individuals have preferential rights over others. The result is a dominance hierarchy in a population. Dominant animals have first choice of desired resources (often including space and territory) and of mates. The dominance may be accepted, without open conflict, by subordinate animals, or it may be contested, often repeatedly. Oftentimes, the subordinates to a dominant individual may then dominate other individuals lower in a hierarchy. Much of the early research was done on domestic fowl (leading to the term "pecking order" becoming a vernacular term in wide usage) but dominance hierarchies occur in a wide range of animal species, including humans. Dominance hierarchies have been documented in most primate species, in social bees, in the sea anemone, in wallabies and in coyotes, wolves and wild dogs. Dominance hierarchies have been...