Out of Africa vs Multiregional Theory

Out of Africa Theory and Multiregional Continuity Theory

• Two theories explain the origin of modern humans: Out of Africa (OOA) and Multiregional Continuity (MRC).
• OOA states that modern humans evolved in Africa and migrated to other regions, replacing existing populations (like Neanderthals).
• MRC proposes that different groups of humans in various parts of the world evolved in parallel, with gene flow preventing separate species formation.
• Anatomical evidence supports OOA: Significant differences between Neanderthals and early Homo sapiens suggest limited interbreeding.
• Archeological evidence also supports OOA: "Creative explosion" of tool diversity, elaborate burials, and art development occurred primarily in Homo sapiens.
• Recent genetic evidence strengthens OOA: Neanderthal DNA is distinct from modern humans, with limited interbreeding. More genetic variation among African populations supports their origins as the starting point of human migration.
• While the OOA is generally accepted, some scientists suggest a hybrid incorporating parts of both theories, acknowledging potential interbreeding.
• Neanderthal DNA found in modern humans is estimated to be around 2 percent.

Freud's Psychoanalytic Theory

• Sigmund Freud's theory of psychoanalysis emphasized sexuality as a driving force of human behavior.
• Initial theory included life-preservative instincts (survival needs) and sexual instincts (culminating in reproduction).
• Freud later combined these into "life instincts" and added a "death instinct".

William James's Psychology of Instincts

• William James's theory of instincts differed from Freud's, emphasizing a broader range of innate behaviors.
• Instincts were defined as automatic actions with no prior learning or conscious intent.
• James argued that humans have numerous instincts beyond those recognized by other psychologists.
• His list included basic reflexes, social behavior, curiosity, and parenting, with specific variations within each instinct.

Rise of Behaviorism

• Behaviorists, like James B. Watson and B.F. Skinner, rejected the importance of instincts and emphasized learning.
• Classical conditioning (Watson) proposed that neutral stimuli can become associated with other stimuli, evoking specific responses.
• Operant conditioning (Skinner) held that reinforcement or punishment following behavior determines its future occurrence.
• Behaviorists believed that humans are general learning machines with few innate qualities, and all behaviors can be shaped by environment.

Influence of Cultural Variability

• Early cultural anthropologists, like Margaret Mead, highlighted the diversity of customs and behaviors across cultures.
• Research on "cultural paradises" emphasized the influence of culture on shaping human behavior.
• Subsequent research revealed flaws in these early studies, finding many universal human behaviors despite cultural differences.
• Male sexual jealousy, common emotional expressions (like fear and joy), and love are examples of human universals across cultures.

Challenges to Behaviorism

• Research by Harry Harlow on monkeys raised in isolation with artificial mothers challenged the behaviorist theory.
• Monkeys preferred the terry cloth mother for comfort, despite the wire mother providing food.
• This suggested that innate needs (like comfort) can override learned associations based purely on reinforcement.
• These findings further challenged the idea that humans are blank slates solely shaped by environment.

Radical Behaviorism

• Rats given radiation hours after eating a specific food learned to avoid it in one trial
• Rats did not learn to avoid stimuli like buzzers or light flashes paired with nausea
• Rats are predisposed to learn certain things, like avoiding food that makes them sick
• Some fears, like snakes, are easy to condition, while others, like cars, are difficult
• Behaviorism was violated, suggesting internal factors influence learning

Cognitive Revolution

• Cognitive revolution looked inside the head, not just at external factors
• Computer science inspired information processing framework
• Information processing framework describes how mechanisms take input, transform it, and produce output
• The human brain is composed of programs that process information
• Cognitive level of description is helpful even without understanding all brain mechanisms
• Humans are not domain-general information processors, they are specialized for specific tasks

Evolutionary Psychology

• Humans come equipped to process specific information
• Evolutionary psychology describes how the mind is designed to solve problems of survival and reproduction
• Evolutionary psychology is a synthesis of modern psychology and modern evolutionary biology

Natural Selection

• Evolution involves changes in organisms over time
• Natural selection explains how change occurs: variation, inheritance, and differential reproduction
• Natural selection favors inherited variations that lead to higher reproductive success

Sexual Selection

• Sexual selection explains the evolution of traits related to mating success
• Intrasexual competition: males compete for access to females
• Intersexual selection: females choose mates based on preferred traits

Modern Synthesis

• Modern synthesis combined Darwin's theory of natural selection with Mendel's theory of particulate inheritance
• Genes, the fundamental unit of inheritance, are passed intact from parent to child

Ethology

• Ethology studies animal behavior within an evolutionary context
• Focuses on the origins and functions of behavior

Inclusive Fitness

• Inclusive fitness includes the effects of an individual's actions on the reproductive success of genetic relatives
• Promotes a "gene's eye" view of selection

Adaptation

• Adaptations are traits that are efficient, reliable, and precise
• They are selected for due to their survival or reproductive benefits

Misconceptions about Evolutionary Theory

• Evolutionary theory does not imply that human behavior is genetically determined
• Evolutionary theory does not imply that human behavior is unchangeable
• Evolutionary theory does not imply optimal design

Human Evolution

• Humans are mammals that evolved over 200 million years
• Our primate lineage began 85 million years ago
• Bipedalism evolved 4.4 million years ago
• Tool use began 2.5 million years ago
• Humans are complex organisms with a long evolutionary history

Psychology and Evolution

• Evolutionary ideas influenced early psychology
• Radical behaviorism emphasized general principles of learning over evolutionary explanations
• Cognitive revolution brought back internal factors and information processing
• Evolutionary psychology combines modern psychology and evolutionary biology to understand human behavior

Explore the two primary theories of modern human origins: the Out of Africa Theory and the Multiregional Continuity Theory. This quiz examines the anatomical, archaeological, and genetic evidence that supports these theories and helps delineate their differences. Test your understanding of how these theories explain the evolution of our species.