Evolutionary psychology is a multidisciplinary field that investigates the psychological adaptations and behaviors of humans in relation to changes in their physical and social environments. It combines principles from evolutionary biology and cognitive psychology. In 1859, Charles Darwin introduced the theory of evolution by natural selection, which explained how organisms adapt and evolve. According to Darwin’s theory, all living beings, including plants and animals, have a common ancestor and go through transformations over time through natural selection. This theory emphasizes how organisms deal with different environmental challenges.
Darwin’s theory of natural selection states that organisms with advantageous traits are more likely to reproduce and pass on these characteristics, allowing them to thrive in a changing environment. Organisms with genetic traits that improve their chances of survival are considered to be naturally selected.
One study that demonstrated adaptive behavior was conducted by Charles & Bargh (1999). They examined how humans tend to mimic the behavior of others in social situations, which they referred to as the “Chameleon effect.” This effect refers to unconsciously adopting the postures, gestures, and mannerisms of our interaction partners. By mimicking each other, we strive to fit in and belong, which increases our chances of survival and reduces the risk of depression. Charles & Bargh (1999) specifically investigated the occurrence of the chameleon effect during interviews.
The hypothesis of the research was that participants/interviewees would display increased foot-tapping and face-rubbing behaviors when interacting with an interviewer who exhibits these actions compared to an interviewer who does not. The study had two conditions: one where the interviewer showed foot-tapping and face-rubbing mannerisms, and another where the interviewer did not. The researchers utilized the chameleon effect concept to propose that unconscious imitation of behaviors, like foot-tapping, helps foster rapport and social bonding between people.
According to Charles & Bargh (1999), a study revealed a significant correlation between the interviewer and interviewee in terms of foot-tapping and face-rubbing. The study showed that foot-tapping displayed a stronger positive correlation, increasing by 50%, whereas face-rubbing increased by 20%. This research provides evidence for the presence of mimicry in humans, supporting the idea that unintentional mimicry and imitation contribute to social bonding. Nonetheless, the study conducted by Charles & Bargh (1999) had both strengths and weaknesses.
The strengths of this lab experiment were its standardization and control, making it accurate and reliable. Another advantage was that participants were unaware of the experiment’s aim or hypothesis, reducing demand characteristics. However, the experiment only involved a western sample, potentially leading to differences in behavioral patterns. Additionally, it was initially unethical as participants were not informed about the study, although this was later justified to them. Fear? Disgust? These emotions are rooted in our genes. Evolutionary psychology sheds light on our current self.
The text suggests that both our genetic makeup and the experiences of our predecessors hold valuable insights into our own characteristics, encompassing fears, emotions, and desires. Anthropologist Dan Fessler concentrates his research on exploring the significance of the ‘disgust emotion’ in the survival strategies of our ancestors. He posits that this powerful emotion aided them in evading potential threats and individuals to ensure their survival and imparted these sensitivities to future generations. To support his hypothesis, Fessler conducted experiments specifically targeting pregnant women.
In a study conducted by Fessler et al (2005), the researchers aimed to explore the protective function of disgust in women during the first trimester of pregnancy, a period known for its risks. The hypothesis was that feelings of nausea and loss of appetite experienced by pregnant women may have evolved as mechanisms to protect both the mother and fetus from potential harmful diseases. The primary goal was to determine if disgust sensitivity during early pregnancy surpassed expected levels. To accomplish this, a web-based survey was distributed through websites focusing on pregnancy, with 691 women effectively participating.
No reward was given for participating. The average age of the women was 28.1 years. The survey requested participants to rate their current level of nausea on a 16-point scale. They also responded to questions to evaluate their sensitivity to disgust in eight different domains, including food, contact with animals, body products, contact with dead animals, hygiene, and contact with toilets.
Based on the hypothesis, women in the first trimester displayed significantly higher levels of disgust sensitivity compared to those in the second and third trimesters. This distinction was particularly noticeable in situations involving potential interaction with others or consuming contaminated food.
Questionnaire data may not effectively measure disgust, but it would have been more reliable if participants interacted with real objects that elicit disgust. However, the results indicated that nausea and vomiting are evolved behaviors meant to reduce pregnant women’s consumption of hazardous foods. From an evolutionary perspective, mental disorders can also be explained. These disorders encompass emotional experiences such as anxiety, depression, and anger.
Abnormal emotions, lacking evolutionary advantage, are deemed as atypical. Depression is a mental state characterized by diminished energy and difficulties in sustaining interest or concentration in life. The debilitation experienced by individuals with depression makes it hard to grasp the potential benefits of such emotions. Nonetheless, nature has created mechanisms for regulating emotions that occasionally lead to experiencing typical but meaningless distress. As a result, clinical depression is considered a pathological condition indicating significant brain dysfunction.
As individuals age, the probability of encountering organ dysfunction increases. Adolescents and young adults have lower rates compared to the elderly who have higher rates. These patterns are consistent with evolutionary aging theories that propose a decrease in selection against dysfunctional traits as survival into old age becomes less likely. Evolutionary psychology plays a role in evolutionary medicine by examining how behaviors and mental conditions, including depression, may have evolved as adaptations to repetitive reproductive challenges faced by our ancestors.
According to the hypothesis, depression is an evolutionary response that aims to prevent infection in both the individual experiencing it and their relatives. Initially, depression helps conserve energy and redirect it towards boosting the immune system’s effectiveness. Additionally, it discourages social interactions and activities that may result in transmitting infections. Similarly, depressed mothers may engage less with their children, reducing the chances of spreading infections to other family members. Lastly, the decrease in appetite associated with depression could also lower the likelihood of encountering parasites found in food.
A recent study conducted by scientists from the University of Las Palmas de Gran Canaria and the University of Granada demonstrated a significant correlation between fast food consumption and an increased likelihood of developing depression. The study, which analyzed 8,964 participants involved in the SUN project who had no prior history of depression or use of anti-depressant medication, found that over a six-month period, 493 individuals either received a diagnosis of depression or began using anti-depressant drugs.
Recent research indicates that regular consumption of fast food can greatly increase the likelihood of experiencing depression. Those who frequently partake in fast food are 51% more likely to develop depression compared to those who rarely or never consume it. Additionally, the study found that individuals who consumed larger quantities of fast food were more prone to certain characteristics such as being single, having a sedentary lifestyle, and practicing unhealthy eating habits. Moreover, it was noted that people in this group often smoked and worked long hours. The connection between fast food consumption and depression is so significant that the risk of developing depression rises with an increase in the amount of fast food consumed.
Evolutionary theory suggests that our ancestors’ food preferences evolved through natural selection to aid their survival in various environments. As a result, our digestive system has adapted over time to efficiently process and utilize necessary nutrients. Food preferences are considered an instinctual adaptation designed to locate energy-dense foods. These evolutionary adaptations are believed to have primarily taken place during the Pleistocene Era, spanning from 10,000 to 2 million years ago.
The preference for energy-rich, fatty food in an environment with periodic food availability may be the reason why people overeat and become overweight nowadays. According to Burham & Phelan (2000), our ancestors had a tendency to consume high-calorie, fatty foods to ensure their survival when there was limited access to food. This preference for calorie-dense foods remains today, despite the fact that fatty foods are now more readily available, which explains our inclination towards unhealthy eating habits. However, this argument does not account for the slow rate of evolution in present times.
The absence of a hunter-gatherer culture in Western societies could result in a decrease in the craving for fatty foods that can potentially lead to health problems. This change also has social implications as it shifts the responsibility for overeating away from individuals and may serve as an explanation for obesity. Evolutionary psychologists suggest that our preference for sweet-tasting foods is a result of our evolutionary adaptation to avoid consuming harmful substances. This explains why many people enjoy sweet foods, which are often calorie-rich but rarely toxic. On the other hand, bitter tastes often indicate poison.
Humans have 27 bitter taste receptors and only 2 sweet ones, indicating a greater sensitivity to bitter tastes. Nevertheless, the sensitivity to bitter tastes diminishes with age. Dr. Gillian Harris conducted research demonstrating that newborn babies have a natural inclination for sweet substances and a dislike for bitter substances. Moreover, this preference is consistent globally, implying an evolutionary basis. The reasoning behind this can be attributed to early mammals primarily consuming fruits, resulting in sweet foods like fruits activating the release of pleasure-inducing dopamine.
Vise versa, bitter foods are usually disliked because they often contain poisons. In contrast, salt is crucial for our survival as it helps prevent dehydration and is commonly enjoyed. While carnivorous animals like lions do not have a strong desire for salt because raw meat provides enough of it, herbivores need salt because their grazing foods are lacking in it. However, this does not elucidate the reason why we still have a strong craving for salt even though we consume meat and acquire ample amounts of salt.
Dudley et al (2008) found that ants living in inland areas 60 miles away preferred a 1% salt solution over a sugary one, even if the sugar solution was 10 times more concentrated. However, carnivorous ants did not show this preference because they obtained enough salt from their prey. This finding has also been applied to humans, with researchers suggesting that salt preferences help maintain competitiveness. However, nowadays salt is often consumed in excess, despite the associated health risks such as high blood pressure. Overall, this approach is effective and supported by scientific research.
Regrettably, the approach of making too many statements is overly deterministic as it overlooks individual differences. For instance, not all people have a preference for sweet tastes and some individuals dislike meat. Evolutionary psychologists consider behaviors or traits that occur universally in all cultures as potential evolutionary adaptations. Altruism, which involves selflessly caring for others out of a desire to help rather than obligation or duty, is an enduring virtue in numerous cultures and holds significance in various religious traditions.
The existence of altruism serves the purpose of ensuring the survival of species as self-centered species wouldn’t survive long, leaving behind more selfless individuals. Evolutionary theorists have always found altruism interesting as it is difficult for natural selection to explain why an organism engages in behavior that has a personal cost and benefits others. However, in 1964, Hamilton introduced inclusive fitness, providing evolutionists with a theoretical framework for discussing altruism.
Inclusive fitness, also known as ‘kin selection’, suggests that natural selection favors behaviors that are beneficial to individuals who share our genes, particularly close relatives. Thus, sacrificing one’s life for the survival of offspring can be considered genetically advantageous. However, while kin selection can elucidate certain altruistic behaviors in humans and animals, it does not encompass acts of altruism towards unrelated individuals.
The concept of reciprocal altruism was first proposed by Trivers in 1971 and it aims to explain instances of apparent altruistic behavior between unrelated organisms. Unlike genetic relatedness, reciprocal altruism relies on repeated interactions and the ability to recognize past interactions with other individuals. Social psychologists studying pro-social behavior strive to comprehend the expression of altruism.
Pro-social behavior, defined as actions that benefit others without personal gain or motive, differs from altruism, a form of genuine selflessness. According to kin selection theory, animals are more inclined to exhibit altruistic behaviors towards their relatives rather than unrelated individuals within the same species. This preference is based on the belief that a group consisting of numerous altruistic organisms has higher chances of survival compared to a group predominantly composed of selfish individuals. Consequently, inter-group selection plays a role in both the development and persistence of altruistic behavior.
The concept that group selection might account for the development of altruism was initially introduced by Charles Darwin. Altruism is logical from a genetic perspective because a gene seeks to maximize the number of copies of itself in future generations. One way to achieve this is by causing its organism to behave altruistically toward other carriers of the gene. In 2006, Warneken & Tomasselo conducted an experiment to examine whether humans and captive chimpanzees would offer assistance when given the opportunity. The experiment involved the experimenter clearly communicating to both the chimpanzees and humans that help was needed with something.
The results showed that humans generally help others, while chimps only help when they comprehend the experimenter’s objective. This suggests that helping behavior may be innate and influenced by genetic factors. This is logical from an evolutionary standpoint, as strong social connections enhance the chances of group survival. It is possible that altruism evolved from a common ancestor shared by humans and chimps. However, the study only utilized captive chimps, who may have helped the experimenter because they were familiar with them as their caretaker and knew they provided food.
When it comes to human behavior, there is a distinction between biological altruism and ‘real’ altruism. Biological altruism is defined in terms of the consequences it has on one’s fitness, while ‘real’ altruism is defined in terms of conscious intentions to help others. According to Elliot Sober’s argument in 1994, an action done with the conscious intention of helping someone may not have any effect on their biological fitness, so it wouldn’t be considered altruistic in the biological sense. On the other hand, an action done without conscious intention to help someone could greatly improve their biological fitness. Therefore, both altruism and morals contribute to our survival.
Not as individuals, but as a species. Sexual selection is a type of natural selection but entails selective pressures to choose the right mate. This selection usually pertains to the process of choice among members of the opposite sex. According to evolutionary psychologists, men and women encountered different adaptive problems in choosing a mate, which clarifies sex disparities in reproductive strategies and mate selection. The selection of a suitable mate is a crucial adaptive problem for both genders in ensuring the survival of genes.
Both males and females face challenges in finding a compatible mate, as certain traits can impact reproductive success. This phenomenon is evident in peacocks, where males compete for female attention. According to Darwin, female peacocks have the power to choose their mates, leading to competition among males. Consequently, male peacocks have developed large and vibrant tails that serve as a disadvantage in terms of survival but attract females.
Since females have to invest more in offspring, they are more selective in choosing a mate, causing males to compete with each other for selection. From an evolutionary standpoint, both men and women desire the highest probability of mating with someone who will produce healthy offspring and pass on their genetic traits to future generations. Males are attracted to fertile females, as they possess indications of good reproductive capabilities.
Seeking younger mates is preferable. Conversely, females look for economic security for their limited potential offspring. They are attracted to signs indicating the availability of resources, dominance, and high social standing. Devendra Singh, a renowned professor, conducted extensive research on the evolutionary importance of waist-to-hip ratio (WHR). In 1993, he was the pioneer in introducing and elucidating the role of this ratio as a measure of attractiveness. Singh (1993) posited that WHR serves as a reliable indicator of female age, reproductive status, and overall health.
Participants were asked by Singh to assess 12 line drawings of different body shapes and sizes. The drawings represented four levels of waist-to-hip ratio (WHR) at three levels of body weight. The task was to rank these drawings in terms of attractiveness. Singh’s findings revealed a consistent pattern across all weight categories. Both males and females rated the figure with the lowest WHR (0.7) as more youthful, healthy, reproductively capable, and attractive. The participants considered the figure with a WHR of 0.7 and normal weight to be the most attractive. On the other hand, the underweight figure with a WHR of 0.7 was seen as youthful, but not as attractive or reproductively capable.
Based on Singh (1993), it has been observed that lower waist-to-hip ratio (WHR) is associated with reduced disease risks and increased fertility. Men tend to prefer women with a 70% WHR, which is considered a sign of health and fertility. This experiment is considered highly reliable and the findings are conclusive. However, it should be noted that this study focused on “male-americans” and therefore may not be applicable universally. Nevertheless, subsequent research has shown that a low waist-to-hip ratio is attractive across different cultures.
However, the WHR research received criticism due to the use of sets of line drawings, which resulted in a lack of ecological validity. To address this issue, Henss (2001) conducted a study using morphed photographs that depicted the same female body with different WHRs. The results replicated previous findings, showing that a lower WHR was associated with higher ratings of attractiveness. In 1989, Buss conducted a study aiming to investigate if evolutionary explanations for sex differences in human mate preferences are consistent across cultures with varying ecologies, locations, ethnic/racial makeups, religions, and political inclinations.
Buss (1989) conducted a study to investigate the preferences of males and females for certain characteristics in a mate, and whether these preferences are consistent across different cultures. Buss (1989) gathered cross-cultural questionnaire data from over 10,000 participants in 37 different societies to address the hypothesis of evolved human mating psychology. The results revealed that in 36 out of the 37 cultures, females prioritized financial prospects more than males did. Additionally, it was found that males in all 37 cultures preferred younger partners, while females preferred older partners. Furthermore, in 34 cultures, males considered good looks as an important characteristic, and in 23 cultures, males identified chastity as more significant.
Buss’s research findings provided strong evidence that across different cultures, there are significant sex differences when it comes to mate preferences related to earning potential, relative youth, and physical attractiveness. These findings support the evolutionary theories of human behavior, specifically the idea that mating behavior should differ based on gender due to the distinct reproductive capacities of males and females. The study had a large sample size and utilized two questionnaires, which enhanced reliability and minimized the potential for demand characteristics.
Despite the low ecological validity, the questionnaire responses may not accurately reflect real-life mate selection behavior. Jealousy, an emotion characterized by negative thoughts and feelings of insecurity, fear, and anxiety over a potential loss, particularly in regards to emotional connections. Evolutionary Psychologists suggest that both men and women seek partners likely to remain faithful, but the risks associated with an unfaithful partner differ between sexes.
If a man cheats on his partner, the risk is that his resources will be directed towards the other woman and her children. On the other hand, if a woman is unfaithful, there is a possibility of her getting pregnant, resulting in the male unknowingly investing his resources in offspring who do not share his genes. In the context of evolutionary theory, it can be expected that jealousy will manifest differently in males and females. Females are more likely to be concerned about the male forming an emotional connection with another woman (emotional infidelity), whereas males are generally more concerned about the female engaging in sexual intercourse with another male (sexual infidelity).
Research conducted by David Buss (1992) has supported the evolutionary perspective. Buss conducted a ‘self-report’ study in which both males and females were asked to envision a romantic relationship where their partner was either engaging in sexual activity with someone else or developing romantic feelings for someone else. Participants were then asked to indicate which scenario would cause them the most distress. The findings revealed that females expressed a higher level of distress towards emotional infidelity compared to males, while males tended to be more upset by sexual infidelity than females.
David Buss (1992) utilized physiological measures to objectively examine the level of jealousy in different scenarios. As anticipated, male participants displayed higher heart rates and galvanic skin responses when contemplating sexual infidelity. Conversely, females exhibited the strongest physiological response when faced with emotional infidelity. However, Buss’s (1992) study can be criticized due to the inclusion of American college students as participants.
The sample may not accurately represent the broader population, as college students are younger and have less relationship experience compared to older individuals. Furthermore, a limitation of the study is that participants may have inferred meanings about infidelity. Nonetheless, critics of evolutionary psychology argue that the hypotheses produced are merely contemporary versions of fictional tales. The term ‘just-so’ gained popularity through Rudyard Kipling’s publication of Just-so stories, which consist of fictionalized and intentionally exaggerated animal tales aimed at children and purporting to explain certain characteristics.
The study of evolution and evolutionary psychology has been influenced by animal studies, as animals have shown common behaviors with humans, as noted by Charles Darwin. However, Cardwell argues that studying animals can result in ‘anthropomorphism’, which is the error of attributing animal characteristics to humans and human characteristics to animals. It’s important to consider that although animal behavior may resemble human behavior, it may have different underlying causes.
The issue of defining psychological mechanisms is that for something to be inherited, it must exist. Evolutionary psychologists have identified certain abstract opinions, such as ‘jealousy’ and ‘depression’, as psychological mechanisms. However, these conditions may not actually exist, making it impossible to inherit them. As a result, the entire debate on the inheritance of certain adaptations breaks down. Biological researchers often take a reductionist approach in studying human behavior.
This is a micro-level of research that deconstructs complex behavior into small parts. However, critics argue that this micro approach is too simplistic in explaining behavior. Nevertheless, having a detailed understanding of the components of human behavior is important in comprehending how various factors can interact to influence certain behaviors. “It’s not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change” ~Charles Darwin
