Imagine yourself in a savanna jungle surrounded by dangers everywhere! Snakes slithering in long grass, lions roaring. How are you going to find food for your tribe? In this ancient landscape, our ancestors evolved and adapted to this environment by the hostile forces of nature. You might be surprised if I tell you the mechanisms our ancestors used to hunt animals, attract mates, and defend themselves from predators are still inside you today! Nothing has changed except for the modern environment we live in today.
From our instinctual fears to the complexities of attraction and social dynamics, our everyday actions, emotions, instincts, and decisions are not random, but a legacy shaped by millions of years of human evolution. Evolutionary psychology unravels the secrets behind our behaviors, revealing how our ancient past affects our present-day choices and interactions.
Introduction to evolutionary psychology
Evolutionary psychology is a field of study that seeks to understand human behavior and cognition. It draws on principles from evolutionary biology and psychology to explore how our minds have been shaped by natural selection to solve adaptive problems faced by our ancestors. Evolutionary psychology applies an evolutionary lens to various aspects of human behavior, including mating preferences, parenting strategies, social behaviors, cooperation, aggression, emotions, and cognition. (1)
Natural selection, a theory proposed by Charles Darwin, the father of evolutionary biology, means the genes that can cope better with the environment and survive are selected and transmitted to further generations.
There are three key components of natural selection. The first is variability. In a population of birds, there exist variable characteristics. One bird is larger in size than others, another has distinctive wings, and one bird has a broken wing. The second concept is heritability. Not every characteristic in the bird population is heritable. The feature of the broken wing of the bird is not heritable. The third concept is survival. Traits that are favorable and most beneficial for the survival and reproduction of the species, those traits are selected and passed on to further generations. In this example, the trait of the bird with a distinctive wing type that camouflages better in the environment survives and is passed to its next generation. The weak traits are not passed on and go extinct. (2)
The products of natural selection
The evolutionary process by natural selection yields three products: adaptations, by-products, and noise.
Adaptation refers to the traits that were developed because of environmental pressure. An example is our instinctual fear of threats (snakes). Without fear, humans wouldn’t be able to survive the savannas of ancestral times, with all the snakes and lions and insects around. Fear is an evolutionary defense mechanism to protect us.
With adaptation, we have by-products, which are traits that did not evolve to solve a problem but were carried out with the functional traits (adaptations). Blushing and pleasure in music were not initially intended for their current roles, they are just carried traits. The primitive human brain relies on sound sensitivity and pattern recognition to survive(the sound of a rattlesnake’s tail), attention given to sound allows humans to appreciate the rhythm and melody in music.
Noise or random effects can be beneficial(resistance to certain diseases), neutral, and sometimes but not always harmful(disorders). Random effects do not represent an adaptive benefit like adaptations or by-products, they are evolutionary traits scattered across the population with no clear purpose.
Another example is the shape of the human earlobe. Some people have long earlobes, others have short earlobes. (see Products of the Evolutionary Process)
Fundamentals of core human nature
All species have nature. Honeybees have the instinct to live in social groups. Some species of birds exhibit the behavior of migrating annually. Humans also have a nature that is unique from other species. Since they have encountered different environmental/ selection pressures in the hunter-gatherer age. During the hunter-gatherer age, humans lived in small groups, relied on hunting, and gathering for sustenance, and faced various environmental challenges. These conditions shaped behaviors and traits that have persisted and evolved within human nature. This unique blend of biological and cultural evolution has shaped fundamental aspects of human nature, distinguishing us from other species.
Fundamentals of evolved human nature
Evolutionary psychology analyzes the human mind as a collection of evolved psychological mechanisms. In evolutionary psychology, evolved psychological mechanisms are the functional units of the mind. Evolutionary psychology seeks to find the contexts that activate these psychological mechanisms and behaviors generated from them. But what exactly is an evolved psychological mechanism? It is a set of processes (in the human mind) that is unique in some points. It has solved a survival and/or reproductive problem recurrently in the past. Since it is meant to solve a specific problem, it is based on a tiny piece of information. The input (tiny information) is turned by decision or trial and error into an output or behavior, which can lead to physiological activity. The behavior tells us the exact evolutionary problem humans faced in the past. Let’s review this with an example. We fear snakes, a feeling that exists in all humans. First, the purpose of the fear is meant to protect us from poisoning (survival problem). Second, it is based on a small piece of information —slithery movements from self-propelled elongated objects. Third, when you see a snake, you face two choices: to attack or to run away from it. This leads to a state of physiological activity (activation of the sympathetic nervous system). This behavior tells us the problem of surviving a snake, which was a problem in the past but not in the present.
All behaviors require evolved psychological mechanisms combined with environmental input. The mind is a collection of evolved psychological mechanisms. The number of psychological mechanisms gives the mind behavioral flexibility. Psychological mechanisms are not like rigid instincts. Decision rules are “if, then” procedures such as “if the snake hisses, then run for your life” or “if the person I’m attracted to shows interest, then smile and decrease the distance.” Despite these mechanisms, we have choices. Even in the simple case of encountering a snake, there’s the choice of either attacking it with a stick, freezing in place and hoping the snake will go away, or running away. In general, the more complex the mechanism, the greater the number of response options will be available to choose from. (4)
In addition to these specific mechanisms, humans have evolved several domain-general mechanisms. In the past, we used to cope with variable climate changes. Volcano eruptions, earthquakes, warm weather, and ice age. Theorists propose that a domain-general mechanism is crucial for solving unpredictable and non-repetitive problems.
What is obvious is that our minds cannot be made of only discrete psychological mechanisms that function to solve specific problems. There must be domain-general mechanisms (for solving unpredictable problems) and subordinate mechanisms (to regulate evolved psychological mechanisms). (5,6)
An important point to keep in mind is these mechanisms have led to an optimal successful solution in the past. Now these mechanisms may or may not lead to a successful solution. Consider our strong taste preference for fat and sugar. In the hunter-gatherer stage, these nutrients were scarce and valuable sources. Consuming sugar and fat in the past was beneficial, sugar and fat contain high amounts of energy which leads to survival in a younger age but degrades age in the later years. Fat and sugar are no longer scarce resources. Thus, our strong taste for such substances now causes us to over-consume them, causing disease, and thus hindering our survival.
Therefore, it’s clear not every beneficial behavior and trait in the past can be applied to the present.
Evolutionary approach to human behaviour
We now know that our minds have developed mechanisms for solving past obstacles, which seem to recur in our modern world but in a different context.
- Disgust is an emotion that involves feelings of revulsion and sometimes nausea. First, disgust is evoked most strongly by disease-carrying substances. That means the feelings of disgust protected us from diseases and unhealthy agents in ancient times. Second, these disgust elicitors should be universal across cultures. The empirical resources support both predictions (7)
- Why do we like alcohol? Our main calorie source in the past was ripe fruits. Fruits contain high amounts of two ingredients, sugar and ethanol. Generally, humans have adapted to favor the consumption of ripe fruit, and the desire to drink alcohol is a by-product of adaptive fondness for ripe fruit. (8)
- The use of fire to cook food may have been critical in human evolution in that it functions as a way to kill dangerous microbes and makes certain foods more easily digestible. (9)
- Men desire young women because, over evolutionary time, youth has consistently been linked with fertility. A large body of evidence suggests that men have evolved standards of youth and attractiveness that embody cues to a woman’s fertility. Signals of youth and health are central among these cues—clear skin, full lips, small lower jaw, symmetrical features, white teeth, absence of sores and lesions, facial femininity, facial symmetry, facial averageness, and a small waist-to-hip ratio. These standards of beauty are highly correlated with female fertility and are consistent across cultures. A high fertility rate means a higher survival/reproductive success. (10-13)
- Selecting a long-term mate who has the relevant assets is an extraordinarily complex endeavor, so don’t expect to find simple answers to what women want. Ancestral women who mated indiscriminately were likely to have been less reproductively successful than those who exercised choice. Long-term mates bring with them a treasure trove of assets. Women may be less influenced by money per se than by qualities that lead to resources such as ambition, intelligence, and older age. Women tend to desire a mate who is healthy (physical attractiveness and masculinity), compatible (similar values, personalities, and ideologies), shows good parenting skills (emotional stability, kindness, dependability, and responsibility), can protect her and her children (bravery, prowess, strength, size, height), and most importantly able and willing to invest in her and her children (status, excellent financial prospects, ambition, love, and commitment). Throughout history, women who chose mates with these characteristics have had better survival/reproductive success. (14-20)
It’s important to point out that not every man and woman prioritize these traits equally, and individual preferences can vary widely based on cultural, social, and personal factors. So, these generalizations are not universally true for all individuals.
This table shows the
desired age difference of
men and women’s mates.
It is clear from the table,
men desire women younger
than themselves by 3-4
years on average.
Women want men who are
younger than themselves by
3-4 years on average.
Critiques
The presence of domain-general psychological mechanisms is a great area of debate. Some scientists are brutally against the idea of domain-general psychological mechanisms. As some may state, “Behavioral plasticity or flexibility is evolutionary death”.
The purpose of evolution is to adapt to the environment while consuming the least amount of energy. Natural selection is costly to the organism. It must evolve in a way that it adapts to the environment without consuming huge amounts of energy. With this in mind, domain-general mechanisms are not a cost-effective solution. They result in variable outcomes (behavioral plasticity), which need a lot of energy. Generating many behaviors for similar inputs requires a lot of time and energy. (21)
Also, evolutionary psychology focuses too much on adaptations and not enough on exaptation. Exaptation is when a trait was adapted to serve a function but later was adapted to other functions as well. Like bird feathers that were initially for insulation but later were adapted for flight. (22)
“It is premature to draw any firm conclusions about whether humans possess more domain-general mechanisms in addition to the specific ones.” Says David Buss.
References:
- Evolutionary psychology | Human Behavior & Adaptation | Britannica
- Natural Selection: Definition, Darwin’s Theory, Examples & Facts | Sciencing
- The past explains the present: Emotional adaptations and the structure of ancestral environments – ScienceDirect
- Evolutionary Psychology: The New Science of the Mind, (researchgate.net)
- The Evolution of Domain-General Mechanisms in Intelligence and Learning. (apa.org)
- A Brunswikian evolutionary developmental theory of preparedness and plasticity | Request PDF (researchgate.net)
- Dirt, disgust, and disease. Is hygiene in our genes? – PubMed (nih.gov)
- The Promise of an Evolutionary Perspective of Alcohol Consumption – PMC (nih.gov)
- The energetic significance of cooking – PubMed (nih.gov)
- Adaptive significance of female physical attractiveness: Role of waist-to-hip ratio. (apa.org)
- The influence of colour on visual search times in cluttered environments. (apa.org)
- Attractive Faces Are Only Average – Judith H. Langlois, Lori A. Roggman, 1990 (sagepub.com)
- Physical Attractiveness in Adaptationist Perspective. (apa.org)
- (PDF) Buss, David M. 1989. “Sex Differences in Human Mate Preferences: Evolutionary Hypotheses Tested in 37 Cultures.” Behavioral and Brain Sciences (researchgate.net)
- Courtship and Marriage | SpringerLink
- Review: More Inequality: Christopher Jencks on the Paths to Success on JSTOR
- The evolutionary psychology of human social strategies. (apa.org)
- (PDF) Evaluating Evidence of Mate Preference Adaptations: How Do We Really Know What Homo sapiens sapiens Really Want? (researchgate.net)
- (PDF) Mate choice and human stature: Homogamy as a unified framework for understanding mating preferences (researchgate.net)
- (PDF) Male Facial Attractiveness: Evidence for Hormone-Mediated Adaptive Design (researchgate.net)
- The logic of social exchange: Has natural selection shaped how humans reason? Studies with the Wason selection task – ScienceDirect
22.Exaptation, adaptation, and evolutionary psychology – PubMed (nih.gov)
