1 June 2007

The Personal Face Of Evolution

By Rusty Rockets

Whether we get along with someone on a social, business, or sexual level often depends very much upon our personalities. And as researchers increasingly discover that animals - from primates to mollusks - have personalities, questions quickly turn to the evolutionary significance of personalities, and the advantages (or disadvantages) that different types of personalities confer.

To date, it has proven to be problematic for researchers to link an evolutionary purpose with animal personalities. But a recent piece of research shows that, logically speaking, personality is a result of natural selection, which leads to some tough questions regarding human nature.

What do we mean when we use the word "personality"? In reality, it's an amorphous word. A shorthand way of referring to the vast biological hotchpotch of emotions and behaviors that organisms exhibit. We might think of Sigmund Freud, or Carl Jung and his personality tests that seem to have a ubiquitous presence on the Internet and in glossy magazines. But whatever we associate with personality, few would argue against the idea that having a distinct personality is what makes us unique as individuals. But can the same be said for animals? Not just chimps, dogs and cats; but birds, fish, spiders, and even shellfish.

It sounds like a bit of a stretch to suggest that an insect may have a personality, but this is exactly what researchers from a variety of biological and psychological disciplines claim. "Darwin himself argued that emotions exist in non-human animals, and his evolutionary theory suggests that behavioral traits, including personality, can evolve in just the same way as fins, wings and arms," notes University of Texas at Austin psychologist, Dr. Samuel D. Gosling.

But the whole question of personality gets considerably harder when we ask just where these personalities come from. Are we born with all of the individual behaviors and emotions that comprise our personalities (nature), do we develop them over time (nurture), or is it a mixture of both? Or, as some evolutionary psychologists would argue, is the nature-nurture dilemma just a false dichotomy? These are difficult questions in regard to understanding complex human behavior, as many conflicting factors may be at play. It is for this reason that discovering that simple animals also have personality traits is so significant.

There is no dedicated field for the study of animal personalities but - at the risk of being simplistic - they can be broken down into those who are concerned with learned animal behaviors, such as animal behaviorists, and those who study innate behaviors, such as ethologists. An animal behaviorist would suggest that a species of bird might learn a particular warning squawk while developing in the egg and listening to its mother. Conversely, the ethologist would argue that the bird is born with this ability. In fact, recent research suggests, barring other secondary environmental factors, that animal personalities are determined by genetics, and that personalities can and do evolve through natural selection.

Some researchers believe that the existence of maladaptive personalities makes behavioral traits via natural selection quite a precarious balancing act for many species. It was Stephen J. Gould who caused a bit of a hubbub when he suggested that a maladaptive trait could be offset by a positive one. He used the example of guppies that had to reproduce early so as to avoid being eaten by predators, but then showed that carrying the eggs early made the guppies heavy and sluggish, and easy prey. There are numerous other instances, such as Elizabeth Pennisi's example of the female North American Fishing Spider reported in Science magazine, which ate its male suitor because of its aggressive instinct to catch prey. A practice that, as Pennisi observes, is not a favorable strategy for keeping the species alive. Such examples suggest that the behaviors that comprise animal personalities are inherited, set in stone, and inflexible.

Attempting to prove a hypothesis in favor of evolved personalities is a team of multidisciplinary researchers working at the Santa Fe Institute, who recently published a paper, entitled "Life-history trade-offs favor the evolution of animal personalities," in the May 31 edition of Nature. The paper investigates the evolutionary origins of animal personality - where animal personality is defined as "consistent behavior over time and in different situations" - which involved clearing up plenty of misconceptions about the subject.

The team began by posing a number of straightforward, but pertinent questions, such as; "Why do different personality types exist within a single population given that, at first sight, one would expect one type to be more successful than another?" and; "Why are individuals not more flexible considering that personality rigidity sometimes leads to seemingly inefficient behavior?" The implication here is that if a certain behavior were impinging upon an animal's chances for survival, then you'd expect it to change that behavior - especially if these less efficient animals were exposed to animals exhibiting more efficient behavior.

The reason that they don't, argue the authors, is that their personalities are linked to "risk-proneness or risk-aversion" in regard to their reproductive future. That, they say, is the "common denominator underlying personalities." Translated, this simply means that the greater the stake an individual has in its reproductive future, the more cautiously it will behave in any situation, or at any time - and vice versa.

To this end, the researchers have outlined a model of personality that at the very least identifies risk-prone and risk-averse personalities, in spite of any given situation. "Individuals often differ substantially from each other in their behavior, and these differences are stable over lifetime and correlated across different contexts," explains researcher Max Wolf, from the University of Groningen. "Some tits, for example, are consistently more aggressive than others, and aggressive birds differ from non-aggressive birds in many other respects like foraging behavior or the exploration of novel environments," he added.

There is yet to be a dedicated discipline dealing specifically with the evolutionary significance of personality - perhaps because it is often associated with the "soft" science of psychology - let alone scientists using animal observations to successfully explain human personality and behavior. However, it would be interesting to consider the fallout that would follow a theory of evolution that differentiated risk-takers and risk-avoiders within human society.

Related articles:

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