Evolution and natural selection in human behaviour

Evolution provides a framework for understanding why humans behave in certain ways. It suggests that our brains have developed specific structures and functions over time to help us adapt to challenges in our environment. This adaptation focuses on improving chances of survival and successful reproduction. Behaviours that support these goals become more common across generations.

Natural selection is a key process in evolution. This occurs when certain traits or behaviours give individuals an advantage in surviving and reproducing. Those individuals are more likely to pass on their genes to the next generation. Over time, this leads to changes in the population, where helpful behaviours become widespread.

For example, behaviours that enhance finding food, avoiding danger, or attracting mates are favoured because they increase the likelihood of passing on genes. This process applies not just to physical features, like body size, but also to patterns of behaviour, which evolve in similar ways.

Key concepts in evolutionary psychology

Evolutionary psychologists examine how evolution shapes human behaviour, with a particular focus on genetic and observable traits. They study these to understand why certain behaviours persist across generations.

Important terms in evolutionary psychology

• Genotype - This refers to an organism's genetic makeup, including the specific genes inherited from parents that influence traits and behaviours.
• Phenotype - This is the observable expression of the genotype, such as physical characteristics or behaviours that result from the interaction between genes and the environment.

These concepts help explain how behaviours linked to survival and reproduction are encoded in our genes (genotype) and expressed in our actions (phenotype). They reveal how natural selection favours genotypes that produce adaptive phenotypes, leading to behaviours that enhance reproductive success.

Evolutionary explanation of aggression

Aggression can be viewed through an evolutionary lens as a behaviour that has developed to support survival and reproduction. According to this view, humans aim primarily to live long enough to pass on their genes and to ensure those genes continue in their offspring. When these aims are threatened or blocked, aggression may emerge as a response.

This explanation sees aggression as an innate behaviour shaped by natural selection. Our ancestors who displayed aggression were more likely to survive and reproduce, passing on those traits through their genes. As a result, aggressive tendencies have been retained in humans because they served adaptive functions in the past.

Reasons aggression evolved in humans

• Competition and elimination of rivals - Male ancestors often used aggression to compete with other males and remove competition, increasing their chances of mating and passing on genes.
• Protection of family - Aggression helped protect offspring and partners from threats, ensuring the survival of genetic lineage.
• Resource acquisition - Aggressive actions, such as hunting or defending territory, allowed individuals to secure resources like food, which supported the survival of themselves and their offspring.
• Attracting mates - Displays of strength and power through aggression could make males more appealing to females, who might prefer partners capable of providing protection and resources.

Additional functions of aggression

Aggression also serves to deter threats from others. For instance, responding aggressively to a bully can discourage future attacks, as it signals strength and reduces the likelihood of repeated challenges. This leads to a safer environment for survival and reproduction.

In social groups, aggression helps establish power and status. Stronger individuals use aggressive behaviours, like fighting, to dominate weaker ones and climb the social hierarchy. Higher status deters attacks from others and expands opportunities for reproduction, as powerful individuals are often seen as more desirable mates.

Psychodynamic explanation of aggression

The psychodynamic approach, developed by Sigmund Freud, explains aggression as arising from innate instincts within the human psyche. This perspective views behaviour as driven by unconscious forces, with aggression stemming from a conflict between fundamental biological urges.

Freud's instinct theory

Freud proposed that humans are born with two primary instincts, which are irresistible biological drives influencing our actions. These instincts shape personality and behaviour, including aggressive tendencies.

Freud's key instincts:

• Life instinct (Eros or Libido) - This is the drive for survival, pleasure, and reproduction. It provides the main energy for living and motivates behaviours related to self-preservation and sexual activity.
• Death instinct (Thanatos) - This is the drive towards destruction and a return to a state of calm, ultimately leading to death. It represents an urge to release all internal tensions, which can manifest as self-destructive or aggressive behaviours towards others.

According to Freud, people are born with varying levels of these instincts. For example, someone with a stronger life instinct might have an optimistic view of life and focus on creative or reproductive pursuits. In contrast, a person with a dominant death instinct could exhibit more aggressive or self-harming tendencies, as they unconsciously seek to resolve inner tensions.