Here is an essay on ‘Evolutionary Psychology’ for class 11 and 12. Find paragraphs, long and short essays on ‘Evolutionary Psychology’ especially written for school and college students.
Essay on Evolutionary Psychology
Essay Contents:
- Essay on the Social Behaviour of Apes
- Essay on Human Social Organization and Mating
- Essay on Inclusive Fitness and Kin Selection
- Essay on Reciprocity and Cooperation
- Essay on Parental Investment
- Essay on the Principles of Evolutionary Psychology
Essay # 1. Social Behaviour of Apes:
Evolutionary psychology is ripe with examples from the animal world. Usually, a number of species, many of them quite distant to we humans, are used with each species illustrating a basic principle.
Let us depart from this formula by first examining thumbnail sketches of the social organization, mating styles, and aggression of the three great apes that are our genetically closest relatives—gorillas, chimpanzees, and bonobos. By comparing and contrasting the behaviour of these three species, we can illustrate many of the major issues of evolutionary psychology.
i. Gorillas:
A gorilla community is dominated by a single adult male silverback, although sometimes the silverback will allow a good buddy or two to share his reign. The rest of the group consists of several adult females and their juvenile and adolescent offspring. The silverback(s) vigorously defend their harem against the attempts of single males to entice away one or more of the breeding females.
Young adult males almost always leave their natal group and try to gather a harem of their own. Life is tough for the bachelor. He will either wander alone or join several other bachelors and form a group of their own. Gathering a harem is not easy. By dumb luck, an old silverback may die and the closest bachelor, after fending off attempts by rival males, may claim most of the harem.
More typically, however, the male collects a female at a time by challenging a silverback in an established group and luring a female away. As a result, most males do not mate while the lucky few sire a large number of offspring.
Gorilla mating begins when a female enters estrus. In response to hormones, her labia change colour and swell, and the females “present” their bottoms to the adult male(s) of the group. Because of the social structure, the female gorilla mates only with the silverback(s) in the group. In such a system, paternity is assured—if the father is not the dominant male, then it is his best buddy.
Although gorillas are remarkably peaceful in general, males engage in infanticide in two situations. The first is when a male gains a new female or takes over a whole troop. Here, he will often kill all the infants of his new mate(s). The second situation is more insidious. A male may invade an established harem and kill an infant, despite an aggressive defense from the silverback and the infant’s mother.
When this occurs, a strange phenomenon takes place—within a few days, the infant’s mother will abandon her group and take up with the strange male who killed her offspring! While a human mother would plot murderous revenge, the gorilla mother prefers to desert a male who proved incapable of defending her infant in favour of another male who is more likely to protect her future infants. For the killer, this type of infanticide is a tactic to gain a mating female.
ii. Chimpanzees:
Chimps are organized into communities centered on a cadre of adult males. Males remain within the troop into which they are born and forge strong social bonds with one another. They will travel together, groom one another, and aggregate into opportunistic hunting parties.
Although power politics and alliances are a way of life among the males in a chimp community, the males of a group unite against the males in neighbouring communities. They actively patrol their own groups’ territory to prevent incursion, and they form “party gangs” to raid a neighbouring chimp community in order to kill a male or abduct a female.
Females emigrate from their natal community and become associated with another group of males. Females do not bond with other females or with males as strongly as the males of a troop bond to one another, and they live in home ranges that overlap the troop’s territory. In the dominance hierarchy within the group, all the adult males are invariably dominant to the females.
According to Wrangham and Petersona young male “enters the world of adult males by being systematically brutal toward each female in turn until he has dominated all of them. … In a typical interaction, he might charge at the female, hit her, kick her, pull her off balance, jump on top of her huddled and screaming form, slap her, lift her and slam her to the ground, and charge off again.”
Like gorillas, chimp mating begins with estrus and has three forms. The first and most typical form is for the female to mate promiscuously and frequently with virtually every male in her group. In the second form, which often occurs close to ovulation, one of the high-ranking males may form a short-term, possessive bond with the female.
Here, the male will remain close to the female and use combinations of threats and aggression to discourage her from leaving and to prevent subordinate males from copulating. Both the promiscuous and possessive forms can take place within a single estrous period. The third and rarest form is the consortship.
Like gorillas, male chimps may practice infanticide when a new female joins their group with an infant. Males will gang up on the new female and despite her defense, eventually rip the infant away from her, take it to a secluded area, and kill it.
Essay # 2. Human Social Organization and Mating:
To illustrate predispositions and constraints shaped by evolution, let us compare human social organization, mating patterns, and aggression to those of gorillas, chimps, and bonobos. Imagine, for the moment, the college-aged men and women belonging to a human culture that followed the pattern of gorillas.
There could be sororities and fraternities, of course, but they would take a decidedly different form. Each sorority would be small and headed by a mature adult male who would jealously guard his harem and their offspring from contact with any other college male. In order to keep his females under eye, the male would probably demand that they all take the same classes that he takes.
Perhaps two or three different harem groups may share the same classroom, but there would probably be physical barriers in the room to prevent them from interacting. Otherwise, the males would disrupt the class by their displays, posturing, games of one-upmanship, and even overt aggression to prevent any female in their harem from leaving and/or to entice another female into joining their harem.
Each coed would feel that is quite natural to have sex with the male and have him as the father of her children. Although there may be squabbles among the women, there would be no possessiveness or jealousy about sharing him with the others. Both the male and the females may feel physical and perhaps even emotional attraction to one another. However, the concept of casually dating someone else would never even cross anyone’s mind.
Males without a harem would either live solitary lives or join together into an all-male fraternity. Bachelor males could easily take classes with other bachelor males, but to maintain order, the college would prohibit bachelors from taking courses with harems. If a harem master gets a bit long in the tooth, a bachelor will engage in repeated displays of dominance and aggression with him in order to drive him away and take over the women. If the bachelor succeeds, the females will not follow their former mate and father of their children. They will placidly go with the victor, have sex with him, and have his children.
There would be continual games of dominance between the bachelors and a harem male as he leads his harem and children across campus. Sometimes a bachelor might find a female and her infant isolated from the main group. Here, he might grab and kill the infant despite vigorous protests and attacks from the mother.
It may take a few days for the female to get over this event, but soon she would find herself attracted to her child’s killer and will leave her own harem group to join up with him. There would be no charges of murder or any disciplinary action from the university. The bachelor is doing what any reasonable unattached male would do to try to get a mate.
Now imagine a different scenario. Again, let us again consider collegiate life, but this time, one organized on the basis of the chimpanzee. Here, there are no dominant males with their harems. Instead, there would be very strong fraternities with fierce—perhaps even murderous—rivalries among them.
Sororities, if there were any, would have poor internal organization compared to the fraternities. In general, the women would act a bit more as loners while the males would almost always be found with their buds. Each sorority would be strongly associated with a fraternity.
A coed would go through cycles of heat and sexual abstinence. As she enters heat, the guys would pay closer attention to her and quarrel among themselves to get near her. Although she might prefer some males to others, she would find it very natural to have sex repeatedly with all the frat boys.
She must be careful in spurning someone’s advances; if she protests too much, she may be beaten and raped. As ovulation nears, one of the more dominant males might try to sequester her for himself by challenging any subordinate who tries to mate with her. He may be successful for a while, but he usually fails to inhibit her promiscuity—after all, he cannot guard her 24 hours a day. If she becomes pregnant, she will not know who the father was.
Essay # 3. Inclusive Fitness and Kin Selection:
Sometimes, mothering ring-neck pheasants perform a marvelous act of self-sacrifice. If a large animal trod too close to her nest, she will make a great deal of noise and run through the field flapping her wings. The safest course of action for her is to be silent, run a few steps to build up the momentum for flight and then soar away.
Yet she makes herself deliberately conspicuous to a potential predator and is sometimes caught in the process. Prairie dogs also show similar behaviour. When a raptor soars overhead or a land based predator approaches the colony, the prairie dogs who initially spot the threat stand upright on their hind legs and issue a series of loud barks that act as alarm codes for their colony mates to run post haste to their boroughs. This behaviour assists the colony as a whole, but at the expense of making the signaller conspicuous to the predator.
These are examples of altruism, a behaviour that can reduce the reproductive fitness of the altruist but increase the fitness of conspecifics. Ever since Darwin’s time, altruism posed a problem for natural selection. Certainly any heritable behaviour that reduced fitness should decrease over time.
Just consider a prairie dog colony that consists of 50% altruists and 50% cheats. When a cheater spots a predator, he hightails it to the nearest borough. The odds that the predator eats an altruist are slightly increased because the cheater has just removed one of his own kind from the denominator of vulnerable prairie dogs.
When the altruist spies the threat, she announces her position to the predator and places herself in danger. Both the other altruists and the cheaters benefit, but if anyone is to be devoured, it is once again more likely to be the altruist than the cheater.
Using mathematical models, Hamilton showed that altruism could evolve when altruistic genotypes preferentially benefit other altruistic genotypes over cheater genotypes. The clearest way for an altruistic genotype to do this is to have mechanisms that bias it to work altruistically for close genetic relatives.
Hamilton’s work presented the twin ideas of inclusive fitness and kin selection. Inclusive fitness is defined as the fitness of an individual along with the fitness of close relatives. Your inclusive fitness would be a weighted sum of your own reproductive fitness, that of your first-degree relatives, second degree relatives, etc.
Kin selection refers to implication of inclusive fitness that natural selection can work on the close genetic relatives of the organism actually performing the behaviour. In a loose sense, fitness can be expressed in terms of kinships just as we have seen it being expressed in terms of genotypes, phenotypes, and individuals.
Inclusive fitness and kin selection have been used to explain different human behaviours. The very fact that we humans recognize and pay close attention to genealogy may reflect a cognitive mechanism developed through evolution that helps in kin recognition.
The phrase “blood is thicker than water” has been interpreted as a realistic description of human emotions and behaviours that preferentially benefit kin over others. Several aspects of altruistic parental behaviour may have evolved through kin selection. Continual themes in fiction portray noble parents shielding their young children from potential harm, but evil stepparents threatening their stepchildren.
Daly and Wilson have pointed out how familial homicide patterns agree quite well with kin selection. Although rare, parents do murder a child, but the perpetrator of such a heinous act is much more likely to be a stepparent than a biological parent. Despite the hyperbolic threat “do that again and I’ll kill you” echoed by many a frustrated parent, very few parents ever even contemplate homicide when it comes to their offspring. The inhibition of homicide is not restricted to parents and their offspring.
Ask yourself the following two questions – “In your whole lifetime, which person has shouted at you and hit you the most?” and “Which person have you yelled at and fought with the most?” If you respond like most people, then you will nominate a brother or sister. Yet fratricide is very rare. Humans are much more likely to kill a spouse than an offspring or sibling.
Essay # 4. Reciprocity and Cooperation:
A close cousin to inclusive fitness is the concept of reciprocity and cooperation, sometimes called reciprocal altruism. Traditionally, inclusive fitness and kin selection have been used to refer to altruism towards genetic relatives.
Reciprocity and cooperation deal with behaviour that requires some “sacrifice” but also has beneficial consequences between conspecifics who are not necessarily genetic relatives. Hence, the target of the behaviour—a genetic relative versus another conspecific—distinguishes inclusive fitness from reciprocity/cooperation.
To understand reciprocity and the problem it posed for evolutionists, we must once again consider cheaters. Lions and wolves hunt large prey cooperatively. Although it is mentioned infrequently on the nature shows, chasing, grabbing, and killing large prey is not a safe enterprise.
Zebras kick and bite, wildebeest have horns, and caribou have antlers, so predators can be hurt, sometimes even mortally so, in the hunt. Imagine a cheating lioness who approaches the prey only after it is dead. Would not her behaviour be advantageous? She can participate in the feast but avoids the risk of injury.
If cheating has a selective advantage, then would it not eventually result in the extinction of cooperative hunting? Another problem is how cooperative hunting ever got started in the first place. Most feline predators like the lynx, tiger, cheetah, leopard, and jaguar, make a perfectly fine living at solitary hunting. Why did lions ever develop cooperation?
According to Trivers cooperation cannot evolve alone. It must be accompanied with mechanisms that detect and reward mutual cooperators and detect and punish cheaters. Consider grooming in primates. It serves the very useful function of eliminating large parasites (fleas, lice, etc.) from a hairy monkey or ape.
Imagine that you are a chimp and that a fellow chimp, Clyde, is continually presenting himself to you to be groomed. Being the nice chimp that you are, you groom Clyde every time that he requests it. After a while, however, you notice something peculiar. Whenever you present yourself to Clyde for grooming, he refuses.
Ask yourself how you truly feel about this situation and how you are likely to respond to Clyde’s future presentations. Again, if you are like most people, when Clyde presents to you, you would feel some form of negative emotion that could range from mild exasperation to downright contempt, depending on the type of chimp you are. At some point, you are also likely to refuse to groom Clyde. Evolutionary psychologists would say that this is your “cheat detection and punishment” mechanism in action.
Reciprocity evolves when reciprocity and cheating can be recognized or anticipated and then acted upon. If your roommate, Mary, is cramming for her physics exam, you are likely to bake some banana bread for her when you suspect that Mary will do something nice for you on the eve of your big chemistry exam next week.
But if Mary were the type of roommate who clutters and trashes the place leaving you to do all the cleaning up, then you are likely to feel irritated and aggravated at her. No banana bread tonight! We feel that it is right and just that everyone does their fair share, and as parents, we spend considerable time and effort inculcating this ethos into our children.
One of the strengths of the modern evolutionists is their ability to uncover subtle and non-obvious phenomenon that fit better with evolutionary theory than other theory. You were correct to express skepticism of the Mary example— after all, there is really no way to determine the relative influences of a biologically soft wired “cheat detector” and your upbringing on the behaviour. But consider the following example, taken from Pinker.
Essay # 5. Parental Investment:
Robert Trivers, who first explicated reciprocity and cooperation, also gave us parental investment theory. This theory states that in any species the parent (male or female) that invests the most time, energy, and resources on its offspring will be the choosier mate.
The theory begins by asking the fundamental question of why many species act finicky in choosing mates. Most evolutionists explain mate preferences as mechanisms that genes have developed in organisms to assist in their own (i.e., the genes own) replication.
Triver’s theory maintains that the fastidiousness of mate preferences will be stronger in the sex that expends the most resources in producing offspring. Ordinarily, this will be the female because biologists define a female as the sex of a species that produces the larger gamete. The sex that produces the larger gamete produces fewer of those gametes. Hence, each gamete is more “precious” in a reproductive sense.
In mammals, the female expends more resources on offspring than the male. Fertilization in mammals is internal to the female, offspring development takes place in the female’s uterus, and the female must suckle the infant for a significant period of time. Hence, female mammals should be choosier mates than the males. Indeed, this is always the case.
In species where one sex competes for mating, males compete with other males for the opportunity of having sex with females. Females do not butt heads with each other for the opportunity of mating with any random guy in the herd.
Even in chimps and bonobos, where mating is largely promiscuous, every male in a troop tries quite hard to have a go at any female in estrus. Whenever one sex shuns a mating attempt, it is the female shunning a male and not a male shunning a female.
Parental investment theory, along with the concept of certainty of parenthood, has been used to explain many different types of human mate preferences. Females must commit nine months to pregnancy and then, before the advent of manufactured baby formula, more than a year to feeding a single offspring.
Even if a woman conceived after her first menstruation, she could bear one child per year until menopause, and the most likely number of offspring for a female during most of human evolution was probably no more than five. A human male, on the other hand, has the potential of fathering a baby every single day after puberty.
Female humans are biologically constrained to devote considerable resources to a single offspring; human males lack such constraints. Hence, human females should have more discriminating mate preferences than males.
A litany of empirical observations is used to support of this conclusion. Certainly in our Western cultures, anecdotal observations agree with it. Males are more ready than females to engage in anonymous sex, even to the point of paying for it. Women report more sexual advances made on them by men than men report sexual advances initiated by women.
Consider the following questions—how long would you have to know someone before feeling comfortable going out on a date with that person, and how long would you have to know someone before getting married? Both males and females have similar time frames—a short time frame for dating and a longer one for matrimony.
Now consider this question—how long would you have to know someone before having sex? The average woman picks a time frame somewhere between dating and marriage. Males pick a time frame shorter than dating.
This account of human parental investment, however, faces a real problem—why should men ever stick around at all? If sleeping around with as many women as possible maximizes the reproductive fitness of the genes in a male organism, why would these genes ever develop mechanisms that predispose a man to settle down with a woman? The evolutionists answer to this is that it effectively “takes two to tango.”
Just like the peacock’s tail, men’s behaviour is influenced by women’s mate preferences. If mutations arose that influenced women to prefer men who stuck around, and if there were men who actually did stick around, and if the pairing between this type of woman and this type of man had high reproductive fitness, then females who prefer stabile males would increase in frequency as will males who actually remain stabile.
Essay # 6. Principles of Evolutionary Psychology:
Several decades ago, American psychology held several laws of learning as sacred. One law was equipotentiality and it stated that an organism could learn to associate any stimulus to any response with equal ease. The classic example is Pavlov’s dog who, according to this law, could have learned to associate a bright light to the food as easily as it learned to associate the bell with food.
The two stimuli, light and bell, are equipotent in the sense that given the same learning parameters, both could eventually lead the dog to salivate. A second law was temporal contiguity. This law stated that the presentation of a novel stimulus with a learned stimulus must occur quickly in time. In Pavlov’s case, the food must be presented shortly after the bell was rung in order for learning to occur.
The dog never would learn to salivate to the bell if the food were presented three days after the bell. The third and final law was practice—it took many trials before the behaviour was fully learned.
These laws begin to crumble after a series of fortuitous studies in the 1950s and 1960s by the psychologist John Garcia and his colleagues. Garcia’s initial interest centered on the behavioural effects of low doses of radiation.
In the experimental paradigm, rats were placed into a special chamber for a relatively long time while they were exposed to a constant amount of low level X-ray radiation. To keep the rats healthy, the chamber was equipped with water bottles containing saccharin-flavoured water.
Garcia and his colleagues noticed three important things:
(i) As expected, the rats became sick from the doses of X-rays;
(ii) Quite unexpectedly, the rats stopped drinking the sweetened water; and
(iii) The rats needed no practice to avoid the water—they learned after one and only one trial.
Garcia’s genius consisted in asking one simple question, “Why should these rats avoid drinking the water when the learning situation violated the accepted laws of learning?” According to the Pavlovian tradition, the unconditioned response (sickness) occurred several hours after the conditioned stimulus (sweetened water).
This clearly violated the law of temporal contiguity because the paring of sweetened water and sickness did not occur within a short time interval. Second, there was no need for practice. Most rats learned to avoid the water a single trial.
Garcia abandoned his initial interest in radiation poisoning to focus on this peculiar phenomenon of learning. His general results and conclusions are illustrated by the study of Garcia and Koelling. Here, rats were assigned to one of four groups in a two by two-factorial design.
The first factor was the sensory quality of water given to the rats—it could either be coloured with a food dye and oxygenated with bubbles (coloured, bubbly water) or mixed with saccharin (sweetened water).
The rats in the coloured, bubbly water/shock group eventually learned to avoid drinking the water, albeit after a number of trials. This accords well with the established laws of learning at the time. Rats shocked after drinking sweetened water, however, failed to learn avoidance within the time limit of the study. This fact clearly violated the established law of equipotentiality under which sweetness should lead to just as much avoidance as the visually coloured water.
Curiously, the effect of making the rats sick had showed the opposite pattern. Rats made sick by the coloured water had a difficult time learning to avoid it while rats sickened by lithium learned to avoid the water after one trial. The coloured-water/lithium group followed the established laws of learning because sickness did not occur in temporal contiguity with the water. The sweetened-water/ lithium group, on the other hand, violated the laws just as much as those rats made sick by X-rays did.
The current explanation for this curious state of affairs is that the laws of learning depend importantly on the biological predisposition of a species. The rat has evolved into a highly olfactory creature that perceives the world in terms of smell and taste. Indeed, rat colonies develop a characteristic smell that is used to recognize colony mates and identify intruders.
Rats are also scavengers who dine on a surprisingly wide variety of organic material. Because they locate food though smell, they are especially attracted to rotting fruit, vegetable, and animal matter because of its pungent odour. Rotting food, however, poses a problem for digestion because it can create sickness when it is too far gone.
Rats react to their food in a peculiar way. When a rat locates a novel food source, he seldom gobbles it all up. Instead, he will nibble a little bit of it, go way for several hours, and then return. The rat may repeat this another time or two—a quick taste, a lengthy departure, and then a return—but soon he will return and gorge on the food.
Interestingly, if an experimenter laces the original food source with enough poison to make the rat sick but not enough to kill him, the rat may return but will not eat the food any more. It is usually a quick, one trial learning experience.
Evolutionary psychologists speculate that rats evolved a biological predisposition and a behavioural repertoire to avoid rotting foods that may make them ill. At some point rats that nibbled at a novel food source out-reproduced those who gobbled the whole thing down, presumably because the gobbling strategy had a high probability of incapacitation or even death through sickness.
Similarly, rats who nibbled and learned quickly out-reproduced those who nibbled but took a long time to learn. And what sensory cues would the rat use to bad food from good food? Most likely they would be olfactory cues.
In this way, rats in the Garcia and Koelling study would easily learn to associate an olfactory cue (water sweetness) with eventual sickness but would have a harder time associating a visual cue (coloured, bubbly water) with sickness. Rats who learned to avoid sweetened water when they became sick were biologically predisposed to learn this and to learn it quickly.
Proponents of this interpretation of the data are quick to point out the role reversal that happens in different species. Birds, who are highly visual like us humans, associate visual cues with sickness with the ease that rats learn about olfactory cues and illness. Birds will readily learn to avoid, say, blue food pellets and eat red pellets. When presented with a novel pellet that is half blue and half red, the bird will peck at the middle, break the pellet in two, and then eat the red half.
The general phenomenon has now come to be called prepared learning or biological constraints on learning, a hypothesis that was initially proposed in 1911 by the famous learning theorist, E.L. Thorndike, but was ignored by later researchers. The prepared or constrained part of the learning process is due to the biology that has been evolutionarily bequeathed to a species.
Human Fears and Phobias From the perspective of evolutionary psychology, fear and panic—like most of our emotions—should be viewed as adaptive responses. They may be unpleasant to experience, but they serve the useful function of prompting us to avoid dangerous situations and/ or to energize our bodies for fight or flight.
The relationship between fear and adaptiveness resembles the inverted U- shaped function of stabilizing selection. In general, it is good to be in the middle of distribution. Too little fear could lead to maladaptive risk-taking while too much fear might incapacitate a person.