C180 Chapter 2 Evolution and the Biological Roots of Behavior

C180 Chapter 2 Evolution and the Biological Roots of Behavior

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Western Governors University

C180 Introduction to Psychology

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Chapter 2: Evolution and the Biological Roots of Behavior

Learning Objectives

By the end of this chapter, you should be able to:

• Understand the evolutionary foundations of motivated behavior.

• Explore biological influences on eating habits.

• Examine the biological basis of threat responses and aggression.

• Investigate evolutionary perspectives on mating behavior.

Charles Darwin and the Theory of Evolution

Charles Darwin revolutionized the scientific understanding of life with his theory of natural selection, which he elaborated in his landmark book, On the Origin of Species. The theory proposes several key principles:

This framework explains how species evolve through natural selection, favoring traits that increase survival and reproductive success in a given environment.

The Biological Perspective

The biological perspective in psychology asks fundamental questions about the origin and purpose of behavior. It explores:

• What behaviors do humans share with other species? Examples include curiosity and playfulness.

• What behaviors are unique to humans? Such as complex language capabilities.

Understanding these helps in recognizing the evolutionary roots and adaptive significance of behaviors.

Evolution of Behavior

Our behaviors are deeply influenced by genetic heritage. For instance, identical twins, who share the same genetic makeup, tend to show greater similarities in personality and preferences compared to other siblings, even when raised apart. This highlights the strong genetic component in behavior.

The Comparative Method

One method to understand evolutionary behavior is by comparing human behaviors with those of other animals. For example, if aggression is seen in both humans and other species, it suggests a genetic basis rather than purely cultural influences. Animals typically exhibit fewer cultural effects, allowing clearer insight into inherited behaviors.

The Autonomic Nervous System (ANS)

The ANS regulates involuntary bodily functions such as temperature control, digestion, and heart rate. Mammals and birds are endotherms, meaning they maintain stable body temperatures through internal metabolic processes.

Sympathetic vs Parasympathetic Nervous Systems

These complementary systems maintain bodily equilibrium during changing environmental demands.

Threat and Aggression

Biological Response to Threat

When threatened, the body initiates the “fight or flight” response, a rapid and intense arousal state that mobilizes energy to handle emergencies. This reaction involves activation of the sympathetic nervous system and a surge of adrenaline.

Gender Differences in Aggression

• Males tend to show higher levels of physical aggression, which is linked to testosterone.

• Females are more likely to engage in social forms of aggression, such as gossip or social exclusion.

Territoriality—the defense of space or resources—is a significant cause of aggression, expressed as personal space preferences in humans. These preferences vary across cultures, indicating both biological and social influences.

Learning Aggression

Aggressive behavior can be learned explicitly (through instruction) or implicitly (through observation). Exposure to violence often increases the likelihood of aggressive behavior, suggesting a socialization component alongside biology.

Limits on Aggression

Aggression is moderated by various factors:

• Relative Strength: Individuals often avoid conflict when the opponent is stronger.

• Dominance Hierarchy: Established social ranks limit aggression within groups.

Nature vs. Nurture Debate

A fundamental question in psychology concerns the relative influence of innate biological factors (“nature”) versus environmental and personal experiences (“nurture”) on behavior. Most behavioral traits result from an interplay between these factors.

Mating Behavior

Role of Appearance

Attractiveness plays a key role in mate selection. Cross-cultural studies show common preferences, including:

• Shiny hair

• Clear skin without deformities

• Facial symmetry

• Average facial features with slight deviations may be attractive

Even infants as young as three months prefer attractive faces, suggesting an innate component.

The Matching Hypothesis

People tend to select partners with similar levels of attractiveness and other social attributes such as:

• Personality

• Race and ethnic background

• Social status and education

• Income

• Religion

• Habits

Gender Differences in Mate Selection

Critique of the Evolutionary Perspective

The evolutionary perspective assumes behaviors are mostly innate and shaped by natural selection. However:

• It is difficult to test these claims scientifically because we lack direct evidence of ancestral behaviors.

• Fossil records do not provide behavioral data.

• Despite these challenges, the evolutionary approach introduces valuable questions and data into psychological research.

Final Thoughts: The Biological Perspective

The biological perspective enriches psychology by exploring the physiological mechanisms behind behavior and evolutionary influences. Basic functions such as eating, mating, and aggression are deeply rooted in biology but are also shaped by individual experiences and environmental contexts.

For example, understanding obesity requires examining both genetic predispositions and lifestyle factors, highlighting the complex gene-environment interaction.

While psychology benefits from a biological foundation, it must also incorporate other perspectives to fully understand human behavior.

Contribution of the Biological Perspective

• Offers insight into mechanisms underlying behavior.

• Highlights evolutionary forces shaping behavior.

• Does not explain all aspects of behavior entirely, emphasizing the need for a multidisciplinary approach.

References

• Stanford University Psychology Lectures. (n.d.). Retrieved from http://www-psych.stanford.edu/~ashas/Psych1Lecture3.pdf

C180 Chapter 2 Evolution and the Biological Roots of Behavior

• W. W. Norton & Company. (n.d.). Evolutionary psychology and biological foundations of behavior. Retrieved from www.wwnorton.com