Ethology, which is the comparative study of behavior from an evolutionary perspective, often deals with the drives relating to feeding, sex, care of young, etc. These drives are apparently motivations that spring from a disturbance in the internal equilibrium of an animal. They are modified factors either internal or present in the environment and drives have sometimes been labeled instincts.
A major contribution to an understanding of behavior came from the laboratory of Konrad Lorenz, who with his pupils the discipline of ethology from 1926 to 1939. Their discovery of the underlying innate components of behavior permitted a comparison of behavioral responses among groups of organisms. They also placed behavior in the arena of evolutionary phenomena to be studied as part of a pattern of increased adaptation within species.
Benefits of ethology
The study of behavior is a relatively new division of biology and tends to be more descriptive and less assuredly analytical than other areas. One danger of analyzing the patterns of activity of other animals is the tendency investigators might have to ascribe familiar actions to human motives, desires, and goals. This is particularly crucial in the area of intention, where we really have no capability of determining what an animal wants when it goes through a set of activities. The intensity of the inner push, whatever its nature, is a drive.
WHAT IS BEHAVIOR?
Behavior is a set of activities that orient an animal to its external environment. While behavior is most clearly apparent in terms of an observable series of movements, it may also include internal responses of an adaptive nature.
An organism exposed to excessive heat may move into the shade. At the same time, the organism may also alter the distribution of blood to permit loss of heat through radiation from the surface to the environment.
Behavioral patterns usually center on acquiring food, seeking a mate, caring for young, guarding against danger, and other tasks vital to the life of the individual. Integral to behavior are the nervous, muscular, skeletal, and endocrine systems.
Taxes (sing.: taxis) are simple kinds of behavior, elicited from even single-celled protozoans, that orient an organism to conditions in the environment.
A single-celled euglena tends to swim toward light. This involves an automatic response of a relatively simple nature mediated the light-sensitive eyespot of the organism and is characteristic of a taxi.
Closely related to taxes are kineses (pi.): changes in the rate of movement brought on environmental stimuli.
Among some insects there is an increased rate of activity in dry areas, a decrease in moist areas. Because of the greater movement and consequent increased migratory activity in dry areas, the insects gradually accumulate in moist environments, where their tendency to move away is considerably reduced.
An animal which has not eaten for a long period shows shifts in internal equilibria which are expressed in the behavior of food foraging. Such challenges to homeostasis as a lowering of blood sugar presumably are the internal motivational elements that trigger the hunger drive. Complex neural and hormonal pathways are involved; the hypothalamus seems to be the essential mediator of behavioral drives.
If the animal is ill or in a weakened condition, the drive may be less intense than would be the case for a completely healthy organism. Previous experience might also modulate the intensity of the drive. In the case of higher primates such as humans, a raging snowstorm might very well deter us completely from leaving the house to purchase food even though a need might exist.
COMPONENTS OF BEHAVIOR
Internal capacities for behavioral patterns vary from species to species. Birds can develop a characteristic song, and lions can stalk and capture fast-moving prey. Clearly, there is an innate genetic basis for behavior. However, behavior also changes as a result of experience; interaction with the environment may modify and even elicit specific patterns of behavior. An old conflict about the relative roles of nature (internal genetic programs) versus nurture (environmental influences) has essentially been resolved the recognition that behavior is the result of both innate features of the organism and the interactions with the environment that accumulate during its lifetime.
FIXED ACTION PATTERNS AND RELEASER
Lorenz and Nicolas Tinbergen showed that certain patterns of behavior occur in an unvarying manner and are the innate components that make up the genetically determined behavioral repertoire of the organism.
Fixed Action Pattern (FAP)
A fixed action pattern (FAP) is a constant response to an eliciting stimulus called a sign stimulus. A sign stimulus coming from other members of the same species is called a releaser. If the releaser is a constant physical feature of a member of the population, it may serve to produce stereotyped responses that smooth social interactions within a group and produce a measure of constancy in exchanges among group members.
Among several species of birds, the young nestlings have distinctive markings within their mouths. When they open their mouths, these markings serve as releasers to produce feeding movements the parents. The stuffing of food into the young bird’s mouth is a fixed action pattern innate in the parents that ensures that the young are cared for and the population maintained. The proximal (immediate) cause of the parental feeding behavior is the releaser, but one might argue that an ultimate (final) cause is the necessity to care for the young so that the species may continue. Thus, FAPs may be viewed as mechanisms over time to accomplish significant adaptations associated with survival.
Innate Fixed Action Pattern
In the male stickleback a deep red pigmentation is produced along the ventral surface in the spring. This causes other male sticklebacks to react aggressively when one male invades the neighborhood of another. An exact representation of a male fish without red pigmentation elicits no reaction, but any red object produces a violent reaction. Clearly the color alone serves as the elicitor of aggressive action. The adaptive purpose of the response appears to be the guarding of territory against male invaders from the same species. A limitation in the usefulness of these innate automatic responses can be seen in the fact that this specific FAP was first noted Tinbergen when a red mail truck passed a window of his laboratory in Holland and produced aggressive movements in a male stickleback confined to a tank in the window.
Releasers are conventionally restricted to sign stimuli that serve a communication function among members of the same species. The action of releasers affords a particularly clear illustration of the existence of genetic factors in determining behavior.
Protective behavior is elicited from a hen sounds of distress from her chick. The hen’s response has the appearance of being mediated an understanding of the situation, followed a measured response to it. However, if the chick is in dire straits but the sound is masked a glass or plastic cover, the hen makes no response even though she can clearly see her struggling chick. The restriction of the response to the stimulation of sound alone suggests an innate neural circuit that is responsible for the behavior. Yet even in the relative constancy of the releaser-FAP relation some modification may occur. The condition of the hen, the loudness of the sound, and the presence of other dangers in the environment may alter the degree of response.
MODIFICATION OF BEHAVIOR THROUGH EXPERIENCE
Behavior may be rooted in internal neural circuits that provide the animal with a range of possible responses to specific environmental cues, but these behaviors may be modified considerably experience. At times the animal may be confronted with competing situations and must choose or assign priorities. A hungry animal engages in food-seeking behavior, but if danger looms, the animal usually turns off the foraging activity and flees. A hierarchy of urgencies clearly exists, and danger in most groups exerts a greater effect in marshaling activities than the drive for creature comfort.
Imprinting refers to an amalgam of innate and learned behavior in which an experience or association made during a critical period permanently affects future behavior. First studied Lorenz in terms of parental identification young chicks, it has since been shown to apply to a variety of types of behavior. Lorenz used the term imprinting because the phenomenon resembles a permanent impression made upon the brain the specific association.
Lorenz found that when he separated groups of goslings from their parents and exposed them to a human (Lorenz) who imitated the parental call, the goslings would follow the human as if the person were the natural parent. This phenomenon is called parental imprinting and only occurs during the first two days after hatching. The short period of time during which the organism is sensitive to the imprinting stimulus is called the critical period. It often occurs early in life, but some types of imprinting may also occur in maturity. Parental imprinting also occurs under natural conditions in other species; in mammals olfactory stimuli tend to play a greater role than the visual stimuli usually associated with parental imprinting in birds.
Sexual imprinting occurs during early associations—a recognition of conspecific individuals for reproductive purposes. Lorenz found that his goslings not only followed him as they matured, but that they attempted to mate with him when they achieved maturity. Among some birds, imprinting is also involved in the learning of the characteristic song the male. An innate capacity for mastering a song is triggered exposure to that song or to even a few notes of the song. Since some birds learn their song even when raised in isolation, imprinting is not a universal mechanism for developing the song.
Habituation involves modification of behavior through a diminution of response to repeated stimuli. A loss of receptivity to repetitious stimuli can be useful in preventing a drain of energy and attention for trivial purposes. Rodents respond to alarm calls others in their group, but if these calls are continued and no danger is confirmed, further calls may be ignored.
Conditioning involves the pairing of an irrelevant stimulus with a natural primary stimulus that elicits an automatic response. In time, the animal becomes conditioned to the secondary (associated) stimulus and responds to it as if it were the natural stimulus. This association of FAPs or similar innate responses with new kinds of sign stimuli broadens the ability of an organism to react appropriately to environmental change, since the conditioning process removes dependence on one kind of release symbol for action.
More complex behavior patterns, such as the ability of a rat to learn to run a maze, are due to trial-and-error learning. This modification of behavior is also called operant conditioning, a process demonstrated and studied extensively B. F. Skinner, a Harvard psychologist. The strategy of operant conditioning in the laboratory involves a continuous monitoring of activity, with rewards given for correct bits of behavior and withheld for inappropriate behaviors. Such monitoring eventually produces a complete behavior pattern, such as solving a maze or pressing appropriate sequences of bars to achieve a reward. When a trainer is present, operant conditioning can rapidly produce a sequence of fruitful steps from random movements the introduction of appropriate awards. Under natural conditions, the achievement of a goal is the reward that directs random activities into a behavioral pattern. Trial-and-error repetitions, step step, lead to a final achievement. Once a successful pattern has been learned, it may be passed on imitation.
An extreme case of behavioral modification involves the application of insight or reasoning to a novel situation. If an animal can direct its behavior to solve a problem for which it has no previous experience, then reasoning is involved. Reasoning in humans appears to involve a recasting of an external situation in the imagination and a manipulation of concepts to produce a solution that can be applied to the situation. However, such insight or reason may also be found in other primates.
A chimpanzee is placed in a cage in which a choice piece of fruit hangs from the ceiling. The chimp cannot reach the fruit, but the keeper has placed some boxes of different sizes in the cage. After a short period of head scratching the chimp moves the largest box to a point just below the fruit and then piles the smaller boxes atop this base until it can climb up and reach the fruit. This type of insight is clearly a step beyond operant conditioning.
CYCLIC BEHAVIOR PATTERNS
Many behaviors exhibit a rhythm in their occurrence. Part of the day is spent in sleep and the other part is characterized great activity. Migrations occur at some seasons but not at others. Many animals demonstrate a daily periodicity in activity patterns that are approximately 24 h long; hence, they are called circadian rhythms (circa, “about”; dia, “day”). In humans the natural cycle is closer to 25 h but is adjusted to the 24-h rhythm in the physical world.
Internal clocklike mechanisms have been postulated for this widely occurring phenomenon. The existence of such an internal timer is clearly indicated the cyclic behavior that is observed in organisms from single-celled protozoans and plants to the most recently evolved primates. In single- celled organisms the daily rhythms appear to originate in signals from the nucleus. These rhythms encompass cell division, enzyme synthesis, metabolic cycles, and movement. Once established the periodic activity continues for fairly long periods of time even when the nucleus is removed from the cytoplasm. However, most cells do not continue life too much longer following extirpation of the nucleus, so these findings are limited in their application.
Light and Dark Cycle in Birds
In animals an endogenous timer appears to exist in the brain. Birds are clearly governed cycles of light and dark in the environment, which tends to implicate the pineal and its light-sensitive production of melatonin. Much speculation also centers on the mechanism where a central clock could communicate with other parts of the body to synchronize the totality of responses involved in rhythmic behaviors. Evidence for both neural mechanisms and hormonal effects has been discovered. Presumably, the tidal rhythms (13 h) and lunar rhythms influence the clocks of seashore creatures, involving mechanisms like those that operate in circadian rhythms.
Previous Scientific Studies about Internal Clock
Several studies have been carried out in which human subjects have been isolated from the usual cues that orient an organism to daily periodicities. Such individuals, usually kept in deep caves, are deprived of light and temperature cycles as well as the company of others who manifest daily activity cycles. Even under those conditions of prolonged separation from the “natural” environment, these subjects continue to display a circadian rhythm. It tends toward a period of 25 rather than 24 h, but when brought back to their usual environment and cued daylight-night shifts, the subjects reestablish a 24 h pattern.
Behavioral patterns associated with the reproductive process are particularly intriguing. The communication involved in readying the sexual apparatus is often complex and subtle and may be associated with elaborate courtship rituals.
Seasonal Sexual Behavior
In most organism’s sexual activity is restricted to a relatively short season. This means that mating behavior must be turned on at some point and then turned off at another time. Sexual behaviors involve periodic changes in such internal characteristics as endocrine activity, central nervous status, and the tone of the reproductive tract. But they are also modified such environmental factors as the amount of light available, amount of food present for building up of fat reserves, presence of mates, etc.
Actual mating is generally preceded an elaborate and ritualized courtship, which is often the arena of intense natural selection. In courtship, the strongest and most fit males may lay claim to receptive females, while other males are banished to reproductive oblivion. Similarly, sexual selection, in which the female may exercise some choice in tendering herself to and affixing to herself a desirable male, provides a mechanism for the perpetuation of the fit (as judged through female selection).
The totality of the sexual response, extending even to care of the young, exacts a significant drain on the resources and energy of the organism. It also represents a commitment not so much to the continued welfare of the individual but rather to the long-term survival of the group—in the sexual performance of the individual is the seed of “self-sacrifice” for the greater need of the many. Too great a price for such an unselfish commitment could be maladaptive, which explains the constraints on the time devoted to sex among most organisms. Groups such as humans, which demonstrate a continuous and constant involvement in sexual activity or interest, are believed to derive a secondary advantage from sex—maintenance of communal (family) structure.
Mechanism of Sexual Behavior
Sexual behavior is made up of many diverse components, both innate and experiential. Much of the activity probably consists of FAPs elicited a variety of releasers or external signs. Some aspects of courtship and mating approximate the aggressive activity associated with the repulsion of one male another invading a staked-out territory. At a critical time, releasers tend to channel the aggressive actions into sexual movements when a member of the opposite sex is involved.
The stickleback is a specific example of such a deflection of aggressive behavior into courtship and mating actions. Aggression, however, is never completely obscured courtship and mating behavior. The male drives the female stickleback away from the nest after she has laid her eggs and he has delivered his packet of sperm. Among some insects and several types of spiders, the female kills and may eat the male immediately following mating.
Among many animal groups sexual associations are relatively casual and may occur between any pair. Such a sexual lifestyle is designated promiscuous.
In many birds, on the other hand, sexual pairing is a lifelong association and demonstrates great fidelity. Where a single male service several females, creating a harem, the term polygyny applies. A single female’s mating with several males is termed polyandry.
The degree of interaction among members of a species may vary from the virtually solitary lifestyle of some crickets to the elaborate societies of ants and humans. Through these levels of social structure some measure of communication must exist to bring about behavior that modulates the particular social pattern. This social communication may consist of calls, facial expressions, postural states, or locomotor patterns.
In some cases, cooperative activity is elicited; in other cases, agonistic (competitive) interactions arise. Some behavior is cohesive—bringing members of a group closer together in a physical sense. Other behaviors are dispersive tending to scatter the members of a group. The flocking of birds preparatory to flight or the gathering of the individual members of a herd of cattle into a tight circle under conditions of danger or cold temperatures demonstrates cohesive behavior. The scattering of male birds or wolves as they stake out and defend a territory is dispersive behavior.
Many kinds of behavior involve a struggle between individuals for resources, such as food, mates, or building materials. Since members of a species have similar needs, they are more likely to engage in competition with one another to secure scarce resources. Only rarely does the struggle involve actual combat. Usually the contest involves highly stylized displays of strength in which the agonists (competitors) threaten one another with a variety of aggressive thrusts.
Such as the baring of teeth, loud growling, or fake charges toward the opponent. Such fierce displays, which are merely symbolic, are known as rituals. The development of stereotyped rituals avoids actual bloodletting and could serve as an object lesson for human societies. Ritualized submission behavior soon ensues from one of the combatants, who acknowledges defeat.
Wolves engage in combat increasing the thickness of their fur coat through piloerection, confronting their opponent, growling and baring their fangs, and making short charges. The wolf who has had enough lowers its tail, smooths back its fur, and even exposes its vulnerable throat. These rites of opposition avoid direct combat and enable both members to maintain their fitness and carry their genetic potential to further reproductive opportunities.
Another competitive interaction involves the establishment of a dominance hierarchy or pecking order. This is essentially an arrangement of social status in which ranking arises from random aggressions. In chickens, where it was first studied, a top-ranked hen (alpha) could subdue all others in the flock and control access to food and mates merely symbolic pecks.
A second-ranked hen (beta) could exert similar control over others below her. This ranking continued down to the lowest member, a perpetual victim who had no hens over which to exert control. Dominance hierarchies are useful to all members of the group, since they facilitate interactions without having to go through competitive struggles each time.
Territoriality is another type of competitive interaction involving the acquiring of a fixed neighborhood an individual for an extended period. The territory becomes an arena for carrying out most of the significant life functions and is vigorously defended. Territoriality is a significant mechanism for ensuring that those that are most fit gain access to scarce resources, since the less fit are unlikely to acquire and defend a territory.
Altruism is a characteristic form of behavior among social animals in which one or several organisms sacrifice their own interests for the welfare of the group.
In human societies it is not altogether rare. The soldiers who during battle fling themselves on live grenades to save others are familiar figures in popular literary and cinematic lore. However, human decisions to lay down their lives for others involve a conscious course of action that could hardly be operative in other species. Such self-sacrificing activity in other animals must be made up wholly or in part of innate behavioral patterns. In several species of field rodents, for example, the entire pack is alerted to danger the alarm cries of scouts who linger in the path of danger while warning others to flee. Such altruistic behavior as the care of the queen’s brood workers who have no direct genetic stake in the welfare of the young bees also springs from inherited pathways, since these altruistic roles are assumed without any evidence of learning or acculturation.
In sacrificing itself the altruistic animal also often sacrifices its chance to pass its own altruistic genes on to the next generation. How, then, can genes for altruism be continued in a population? W. D. Hamilton the concept of kin selection to account for the maintenance of genes leading to altruism. His theory began with the recognition that the evolutionary success of a specific gene is dependent not just on the success of individuals who possess that gene, but on whether the frequency of that gene increases in the next generation. To make the distinction clearer, our focus should be on the gene rather than the individual, certainly a novel perspective in scanning for evolutionary change.
Studying Kin Selection
When considering the genes that mandate or lead to altruistic behavior, one must view not merely the reproductive destiny of the altruist but the breeding success of related individuals who carry a similar array of genes. If the activity of an altruist (in sacrificing reproductive privileges for the welfare of the group) increases the fitness of closely related individuals who then spread the altruistic genes into the next generation, altruism will flourish.
Since the core of this explanation focuses on a collective evolution of closely related individuals in a group, the name kin selection was used to describe this series of events. In terms of the survival and success of a gene or cluster of genes, the degree of relationship that exists in the kin group is crucial, since closely related individuals tend to share more of their genes.
Research on the tendency of individuals to indulge in altruism has shown that in many species altruistic behavior is usually extended to close relatives with whom the altruist has common genes. This enhances the overall reproductive success of kin groups or clans. This consideration of the fitness of kin as a group, rather than focusing on individuals, has been called inclusive fitness. It is in the raising of inclusive fitness that continuation of altruism is explained—the altruist may be stymied, but kin carrying similar genes, including those for altruism, are better able to survive and spread their genes.
Among many species, intimate exchanges between members and adaptive cooperative action are facilitated through the formation of permanent social structures called societies. These societies clearly require highly sophisticated mechanisms for communication, a capacity for joining individual needs and behaviors into an integrated superstructure, and the means for ensuring continuation of the society from one generation to the next.
Complex Societies in Insects
Complex societies are most common among insects and vertebrates, especially those vertebrates with highly evolved brains. In the case of insects, social stability is based on a rigid delegation of functions that are carried out in an unvarying fashion. A rigid caste system is present, and the members of each caste demonstrate behaviors that are largely determined innate instinctual components. Little variation task performance can be detected. Integration is usually achieved through chemical interactions among the members of the group.
Among honeybees, as many as 100,000 individuals may make up the community living in a hive. Almost all the members are female. The few males, known as drones, have no function other than to mate with the single queen bee at the time of her emergence from the egg. Apart from the queen and the few drones, the community is made up of many thousands of worker females. This caste may be subdivided into nurse workers, who feed the larvae emerging from the thousands of eggs deposited the queen; housekeepers, who tend and maintain the wax cells and guard against predators; and food gatherers, who leave the hive and forage for food to be used to maintain the community. Although the worker bee lives less than two months, it goes through each of these “occupational” phases.
In vertebrate societies individuals tend to be more independent and less rigidly programmed than their insect counterparts. Dominance hierarchies rather than caste system characterize vertebrate societies. The alpha and beta members of such a hierarchy not only enjoy the privileges of primary access to food and mates but also share the responsibility of protecting both themselves and those lower down in the hierarchy from external dangers.
Among monkeys and apes, social structure tends to be both complex and capable of modification through experience. Variation in basic social structure is particularly marked in human societies, although the mating bond tends to influence family configurations of most societies. Values and the inculcation of social norms among humans involve the development of a culture—ideas and symbols of an abstract nature that are passed from one generation to the next and are often represented in icons, books, works of art, and so forth.
ROLE OF COMMUNICATION
Societies are maintained through continuous interactions among their members. These interactions involve communication, the passing of information from one individual to another. Such information may involve aggressive responses, sexual receptivity, the existence of rare resources in the vicinity, or more subtle feelings or desires. Communication may utilize visual displays, sound, smell, or even taste. Many of the behavioral responses of insects and even those of vertebrates involve the elaboration of chemicals that elicit the responses.
Communication as Defending Territory
Constant communication provides a monitoring of the state of the social structure and permits adjustments to maintain stability. In the case of the honeybee, awareness of an increase in temperature within the hive groups of workers leads to a wild beating of wings within the hive, which tends to lower the temperature. Such a primitive air-conditioning mechanism can be effective only if temperature states are widely and rapidly communicated.
Part of the foraging efficiency of honeybees is the ability of worker scouts to come back to the hive and indicate through a “dance” both the direction and the distance of food sources to those who are ready to seek food. This waggle-taggle dance returning bees was shown Karl von Frisch to supply surprisingly detailed information about the site of such food. The nature of the food could be communicated the regurgitation of nectar the returnee directly upon the outgoing group.
MODES OF COMMUNICATION
Hormones also play a role in communication enhancing drives that produce behavior possessing a significant communicating component. They may also induce the formation of structures that are releasers of drives and behaviors. This is readily apparent in the case of sexual development.
With hormonal changes, structures may appear that act as releasers for courtship, induce mating movements, and help to compose programs for the care of the young. Reciprocal sexual actions depend on a constant exchange of information between the participants. Among humans, and perhaps the apes, secondary sexual characteristics that broadcast the readiness and availability of potential mates for sexual activity are particularly apparent in general body curvature, the prominence of the breasts, and the pitch of the voice. These features are influenced, of course, the sex steroids of the gonads.
In the spring the male stickleback secretes hormones that produce the bright red coloration of his undersurface. When the male, under the continuing influence of these same hormones, seeks out shallow water in which to build a nest, he becomes a ready target for females, who are attracted the red coloration. In turn, the egg-swollen body of the female attracts the attention of the male, and a courtship dance (swim) ensues that culminates in the release of eggs into the nest the female. As the female leaves the nest, the male deposits sperm and stands to assume the care of the soon-to-be-hatched young. Hormones, in this instance, generate all the visual cues that control courtship and mating behaviors.
Pheromones, extremely effective chemical modes of communication, have been called social hormones. Just as hormones circulate within an individual to exert an integrative and regulatory effect on internal functions, pheromones pass among individuals of a group to produce integrative behaviors.
First Discovered Pheromones
One of the first pheromones discovered was the sexual attractant elaborated some female moths, which causes males to fly to the female. As is true for all pheromones, the sexual attractant is a relatively small organic molecule carried in the air and is extremely effective even in minute amounts. Among gypsy moths even a few molecules released the female can attract males up to a mile away. The effectiveness of the pheromone is dependent on the olfactory sensitivity of the target individual.
Role of Pheromones
Pheromones have been shown to function as markers of territorial boundaries, signals for danger, and regulators of caste development in social insects. A particularly interesting case of pheromone function is the “funeral” emanation arising from dead or dying ants. This chemical mobilizes surrounding workers to eject the moribund individual from the colony.
A useful behavior to maintain group health and cleanliness. When this funeral pheromone was isolated and painted on a perfectly healthy worker ant, her colleagues carried her off and deposited her outside the anthill. She returned but was promptly ejected again. After several unsuccessful attempts to regain entry she finally gave up further attempts at reentry. This reflects the highly programmed nature of behavior in insect societies, which leaves little room for novelty or reason.
BIOLOGICAL DETERMINISM AND BEHAVIOR
Biological determinism in the context of this chapter’s concerns is a theory that ascribes major characteristics of an organism and its patterns of behavior to genetic influence. In the social aggregations of insects and primates, the theory proposes that the genes impose a significant constraint on behavior. Although experience and culture are accepted as modifying influences, basic social interactions are viewed as the result of an evolutionary selection of genetic programs.
Expert Scientist’s Point of View
E. O. Wilson, a highly regarded expert on insect societies, proposed (Sociobiology, 1975) that behavior can best be understood if examined from an evolutionary perspective. Even those aspects of human society that have traditionally been studied sociologists and political scientists, such as war, family structure, and norms of citizenship, can be more completely understood as the outcome of a differential survival of genes, according to Wilson.
Considerable controversy rages over this extension of the biological (evolutionary) perspective to the sociological. While flexibility may exist in individual expression of an inherited pattern, many critics of biological determinism maintain that the plasticity (variability) of our social institutions contradicts an interpretation of selection of genetic programs. Criticism is also directed against the implication that only limited improvement of human potentials and talents is possible if our development is channeled and constrained genetic programs selected for past conditions.