It's no accident that human beings exhibit personalities that resemble animals. People subconsciously modulate their behaviors because it helps create stable social organizations. In the same way that durable ecosystems necessarily contain a wide diversity of species -- in which every niche of the food web is filled and re-filled in a delicate game of evolutionary competition -- humans adapt their personalities to fit their environment. In the wild, an overabundance of predatory creatures will wreak havoc on an ecosystem, while the complete absence of predation will result in overpopulation of smaller prey species. Similarly, it seems that the ratio between predators and prey in the wild mirrors the ratio in our own society. People with large animal personalities -- like elephants, giraffes and gorillas -- cannot be supported in large numbers as their bulky personalities put a disproportional stress on the social environment. This is why smaller human personalities like mice, otters, beavers, and sheep tend to dominate the concrete jungle.

The fundamental aspects of animal personalities can be summarized with the four Fs:
Feeding, Fighting, Fleeing and Sex.

Feeding techniques translate into the careers that corresponding human personalities would choose. Bird personalities, for example, would prefer jobs that provide a great deal of freedom, while sheep personalities might flourish under the direction of a strong dog personality. Canine personalities instinctively work well with others while bear personas chafe under the direction of authority.

Fighting is equivalent to the way in which a person controls his or her environment. Carnivorous personalities are assertive and adventurous, while herbivorous personalities tend to be passive and cautious.

Fleeing is how people protect themselves from each other. Herd animal personalities find refuge in the company of friends and family, wolves prefer tightly knit social groups, and mice personalities prefer to keep low profiles.

Sex describes the ways we seek mates. From the brutal strength display of the wild elk to the seductive display of peacocks, all creatures strive to exert control over their reproductive choices. An animal's mating habits translates into the way that someone conducts their sexual relationships. Some animal species are monogamous while others have a variety of mates. Some (beaver) personalities mate for life, while tiger personalities are solitary and rarely monogamous. From the subtle and coy techniques of the cottontail personality to the aggressive displays of the lion, every species employs a unique mating strategy. These sorts of behaviors come naturally to us and a visit to a public park reveals our animal personalities in action. Young girls walk by pretending not to notice the watching boys displaying their own mating behavior, some of whom adopt masculine stances lounging around with their legs apart, or calling aggressively to the females, while others feign disinterest and use subtle body language to stake their claims.

Population Densities
Since stable ecosystems contain a wide diversity of species, it is also important for the ratio of these species to be balanced. In human society, this ratio of predator to prey is often maintained through social pressure. Consider the artificial environment of an overcrowded inhospitable prison. Someone who previously had a combative warthog personality might be unable to survive in a society dominated by crocodiles and lions, and perhaps by backing away from his assertive stance and manifesting the more gregarious personality of a herbivore, he could seek the protection of the herd to survive.

Responding to Animal Instincts
The rules that govern human mating behaviors are instinctive and deeply rooted. In most mammalian species, males reaching middle age find themselves responding to powerful biological urges. Aging silverbacks can no longer compete physically or sexually with the upcoming group of younger males, so in a biological panic, their personalities trigger them to make one last fling. In humans, this manifests itself when middle-aged men suddenly feel the urge to display their wealth, begin workout routines and start ignoring their wives. This middle-aged crisis is example of our response to animal programming, but fortunately humans have the ability to control their behavior and are not completely slaves to their animal instincts.

Animal Magnetism
When a wildcat and a fox get together they exhibit a superficial compatibility and nocturnal spirit. However, as a canine, the cat is a natural competitor of the fox and its natural friendliness grates against the cat's aloofness, so over time these tensions often conspire to destroy the relationship. Likewise, if a mouse personality married a cat, power conflicts or spousal abuse would quickly destroy the union. In general, animal personalities should avoid forming close relationships with their species' natural predator.

However, this does not mean that all herbivorous personalities must avoid predators. The meek cottontail might even strike up a friendship with a powerful lion, since lions are disinclined to waste energy chasing elusive, low-calorie rabbits. Although marriage is out of the question, these friendships can be quite enduring. In exchange for companionship and loyalty, the predator provides resources and protection for the cottontail.

Animal Relations
People tend to relate better with those whose animal personalities share their ranges. For example, the water personality of the dolphin has a great deal in common with the aquatic sea lion and otter, while the pastoral natural of the sheep makes for an ideal mate with a grazing deer. Conversely, animal personalities that live in markedly different environments tend to avoid each other. Birds choose to distance themselves from the land mammal personalities and the unencumbered sea dwellers are awkward mates for complex land creatures. On the other hand, the semi-aquatic beaver is capable of forming relationships with both water-going and land-based animal personalities.