Personality: Evolutionary Heritage and Human Distinctiveness

Arnold H. Buss

• Publisher: Psychology Press
• Year: 2014
• eBook ISBN: 9781317785118
• Topic: Psychology
• Subtopic: History & Theory in Psychology
• Index: Psychology

This innovative study focuses on seven inherent personality traits humans share with primates; activity, fearfulness, impulsivity, sociability, altruism, aggressiveness, and dominance. The author discusses these traits from the dual perspective of our evolutionary history and our human uniqueness.

1	An Evolutionary Perspective

The human species has descended from a long line of animal forebears all the way back to one-celled animals. It is well known that such biological mechanisms as breathing, digesting, and conserving heat have evolved over millions of years. What may not be so well known is that some of our behavioral tendencies have also evolved as adaptations to the environment. We hear in essentially the same way that mice and cats hear. Our response to infants has much in common with the way dogs react to puppies. And we manipulate objects more or less the way chimpanzees do.

Humans are of course mammals and more specifically, primates. As higher primates, we are biologically similar to the three great apes: orangutans, gorillas, and chimpanzees. We share with them sense organs, many modes of perception and learning, many facial expressions, and various social behaviors. It should, therefore, evince little surprise that we may also share personality traits.

Of course, we are different from other animals; notice that we study them and not the other way around. Our language, imagery, and thought processes are advanced far beyond the capabilities of other animals. We make complex tools and cannot survive without them, devise culture, and are shaped by it. We differ from other primates anatomically and psychologically, and we possess personality traits not seen in other species. As a reflection of the differences between our species and other primates and for ease of exposition, the term primate henceforth will refer only to nonhuman primates, usually the great apes.

When details about these and other aspects of the evolution of human behavior are spelled out, how might this evolutionary perspective deepen our understanding of human personality? First, such knowledge reveals those features and personality traits we share with other animals. Like other mammals, human infants develop a strong attachment to their mothers, and like the social mammals, humans are strongly affiliative. Like advanced mammals, especially primates, we have a long childhood. The developmental course of the traits we share with primates and other mammals may be similar, for we have in common not only attachment bonds but also social bonds with peers and struggles for power. To the extent that the developmental course of personality traits is similar in humans and primates, this knowledge should contribute to our understanding of human traits.

Second, the crucial psychological differences between our species and primates, which reside in the area of cognition, can be explored. Our advanced cognitions, together with the culture that such cognitions allow, extend the range of behavior and allow the addition of cognitive components to particular personality traits. For example, to foreshadow a later discussion, we are capable of not only physical aggression but also verbal aggression; the human personality trait of aggressiveness has a verbal component not present in the animal trait of aggressiveness.

Third, when we examine human behavior as part of a sequence that has slowly evolved over millions of years, we become aware of important trends. To take just one example, when we examine the evolutionary line from lower mammals to humans, we see that hormones become less important determiners of behavior, which is increasingly shaped by individual experience. Thus when we find sex differences in personality traits, we are more likely to examine socialization practices, cognitions, and learning for an explanation in humans but more likely to focus on hormones as an explanation in animals. Of course, favoring psychological and sociological explanations for human behavior because of evolutionary trends does not deny biological explanations nor preclude their use, as will be seen.

In brief, an evolutionary perspective focuses attention on our animal heritage and the evolutionary trends in the line that led to our species. Where shall we look to discover our animal heritage? An obvious starting point is other members of our group, the primates. Of these, the most relevant comparisons are with the primates closest to us, the great apes. More specifically, the great ape that most resembles us and has received the greatest attention from scientists is the chimpanzee. Therefore, the behavior of the chimpanzee is taken as the model for primate behavior, not because chimpanzees are typical of primates but because their behavior is most likely to inform us about human behavior. Also, the general tendencies observed in primates are not neglected.

What follows are accounts of broad behavioral tendencies and evolutionary trends. These accounts are based on research on mammalian, primate, and human behavior, but many of the statements go considerably beyond the extant data base and therefore should be regarded as a theoretical integration of current knowledge.

PRIMATE BEHAVIOR

Primate behavior has been shaped by evolutionary processes. Primates share some behavior with other mammals, but they are closest in behavior to the highly social mammals. And some features are distinctively primate.

Behavior Shared with Most Mammals

Like other mammals, primates follow a circadian rhythm of activity, which descends to a low ebb at night during sleep and reaches various peaks during the day, usually before feeding. During the day there are also intense bursts of energy in aggression, escape, sexual behavior, or just frisky play. Within any particular species, there are marked individual differences in the level of energy expenditure, which are well known to owners of pets. Thus some cats are mobile, and others are lethargic. Less vigorous breeds of dogs—basset hounds, for example—are more docile and easier to handle. The more vigorous dogs—terriers, for example—are so active that they are best kept outdoors where they can roam freely. These extremes are just the opposite ends of a dimension of activity, which presumably was more normally distributed in the ancestral stock that gave rise to these various breeds after thousands of generations of human control.

Many mammals move around and investigate the environment, a tendency that is especially strong in the line from which primates evolved. Such exploration brings them into contact with unfamiliar animals of their own species and members of other species. Then they are wary and less mobile. Thus when the chimpanzees at Gombe first saw Jane Goodall, they retreated and kept their distance, though her behavior objectively posed no threat (Goodall, 1986). Exploratory behavior temporarily diminished but slowly returned to its previous level. Only after many months of her continued presence were they able to overcome their shyness and allow her to approach closely and occasionally interact with them.

Such shyness may be just one component of a more general tendency of fear. When a young primate is exposed to excessive social novelty, temporary abandonment, or threat, it reacts by howling, shrieking, clutching, and kicking. Puppies and kittens tend to wail and whine. Despite species differences among mammals in the expressive display of fear, there is a common set of reactions triggered by activation of the sympathetic nervous system: increased rate of breathing, higher blood pressure, and shunting of blood from the digestive system to the skeletal muscles—all preparations for flight. Primates and other mammals also may become afraid when confronted with nonsocial stimuli such as loud sounds and sudden movements.

Primates share with other mammals a behavioral repertoire of aggressive responses. The fighting of cats and dogs is well known, against both their own kind and members of other species. Attacking behavior usually occurs when an animal’s territory is invaded, when predatory acts will yield a meal, or when the animal is attacked and must defend itself. Earlier field studies of chimpanzees found them to be gentle and nonviolent, but later research has revealed clear patterns of aggression (Goodall, 1986). Though males tend to be the more aggressive sex, females sometimes attack and threaten others.

Like other mammals, primates display sex differences, not only in size and aggressive behavior but also in reproductive behavior. Females have estrous cycles that drive variations in sexual motivation. At ovulation they tend to initiate sex if males do not anticipate them. When not ovulating, female dogs and cats rarely are interested in sex. Males, as is well known, are usually ready for sex and may attempt it even with females who are not ovulating.

Females bear and rear the young; males contribute sperm and little else. One consequence is that females stay close to their young, both as nursing mothers and as protectors, responsibilities that limit the freedom and mobility of females. Another consequence is the development of a close attachment between mother and infant, but in the less sociable mammals this bond does not outlast the infancy of the offspring.

Behavior Shared with Highly Sociable Mammals

Primates are part of a group of mammals that are highly sociable; some of the best examples are elephants, dolphins, and dogs. They prefer to associate with one another and become upset when cut off from companionship. Dogs mourn for their masters, and chimpanzees may become depressed by the absence of their companions. After social isolation, reunion elicits not just relief but also elation. Dogs greet comrades by nuzzling and licking each other; primates seem to enjoy grooming others and being groomed.

All mammalian young are born helpless and must receive nurturance for some time. For primates, this period continues for several years, until the young have sufficient instrumentality for self-help. The young develop a strong tendency to seek help, and their mothers have a strong tendency to be nurturant. Some infants tend to remain dependent as they mature and may display succorant behavior into adulthood, though usually in diminished form. Some mothers may be compassionate and helpful with unrelated animals, and some males may be helpful and protective of their young companions. Thus there are individual differences in nurturance.

Primate infants may become accustomed to being the sole focus of the mother’s affection and refuse to share this affection with others. When the mother gives birth to the next child, the older sibling may become intensely jealous. Jealousy is not limited to the young, however, and is a potential consequence of any close bond of affection. Pet dogs have been known to display jealousy when another pet is introduced into the household or even after the birth of a child. And among highly social mammals, a close bond of friendship or love can exist among adults. Adult primates, especially the great apes, show affection to friends by grooming, hugging, patting, or even kissing.

The potential for aggressive behavior, mentioned earlier, may be one reason that affiliative animals tend to have some sort of social organization, usually one based on dominance. Larger, stronger animals tend to enforce their will on small, weaker members of the group. Being dominant usually means having better access to food, to attention from others, and often to females. Dominant primates tend to be groomed by subordinate ones. Also those who associate with a dominant animal, either as a companions or as sex partners, may share some of the ascendant animal’s status.

The simplest kind of dominance hierarchy is linear: A coerces B, who threatens C, and so on. Such a hierarchy is usually established among dogs by the playfighting and occasional real fighting of childhood and adolescence. (Cats are less social, so that though one cat may dominate another, a congregation of many cats is so rare that no dominance hierarchy is ever needed or established.) Among sociable mammals, and especially among primates, the linear dominance hierarchy may be broken by the particular experiences of the maturing animals. Nonlinear dominance may also occur because of coalitions, clusters of a few animals who can deliver concerted threats or attacks. How a coalition works has been described by de Waal (1982), who closely observed a colony of chimpanzees. Luit was the alpha male, Nikki was number 2, and Yeroen was number 3. During the course of several months, the second and third males gradually formed a partnership directed against the alpha male: “Both Nikki and Yeroen became less submissive towards Luit and resisted his interference more and more frequently. When the leader displayed at the two of them, they were no longer intimidated. Yeroen began to scream and furiously attacked Luit while Nikki kept close to Luit with his hair on end, as if he were threatening Luit” (de Waal, 1982, p. 128). Such confrontations eventually eroded Luit’s dominance so much that Nikki became the alpha male, though he was careful to maintain the coalition with Yeroen.

The concepts of dominance and status seem necessary to account for the social organization of primates and other highly social mammals. Dominance refers to the animal’s position in the group that derives from its own strength and ferocity or the power of a coalition. Status refers to the position and privileges of the animal, which derive not only from dominance but also from age (older animals have higher status), reproductive status (ovulating females have higher status), and even genealogy (rank of the mother). Genealogy is more important for females, whereas dominance through fighting is more important for males.

These issues have implications for personality. Individual differences in dominance are both determiners and consequences of aggression, leadership, and confidence. As determinants of personality, gender and social status appear to be important not only in humans but also in primates.

Distinctively Primate Features

None of the behavioral tendencies described here is unique. Rather, they represent extensions of features seen in lower mammals. Many mammals, such as cats and dogs, are inquisitive and wander about their environment. This tendency to explore, mentioned earlier, contains an element of curiosity, but primates are much more curious. They tend to sniff, taste, and examine nearby objects, and they must know what is up that tree or over that hill. In the laboratory, they will work to receive stimulation. Chimpanzees are known to solve puzzles and other problems in the absence of any extrinsic reward, just to satisfy an insatiable curiosity. There is an anecdote about an experimenter who used banana slices to reward a chimpanzee for solving problems. The animal was not hungry and just lined up the banana slices as he solved the problems, but eventually the experimenter’s supply was exha...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• 1 AN EVOLUTIONARY PERSPECTIVE
• 2 DETERMINANTS OF PERSONALITY
• 3 ACTIVITY
• 4 FEARFULNESS
• 5 IMPULSIVITY
• 6 SOCIABILITY
• 7 NURTURANCE
• 8 AGGRESSIVENESS
• 9 DOMINANCE
• 10 INTEGRATION
• REFERENCES
• AUTHOR INDEX
• SUBJECT INDEX