Psychology Chapter 2: Evolution, Genetics, and Experience

Origins of Dichotomous Thinking

• The concept of dichotomous thinking emerged in Western culture, where the Church's views were considered true.
• Around 1400, changes occurred with the plague, famines, and other events, leading to a shift in thinking.
• René Descartes (1596-1650) advocated for a philosophy that divided the universe into two parts:
  • Physical matter (behaves according to natural laws and is suitable for scientific investigation)
  • Human mind (soul, self, spirit; lacks physical substance, controls human behavior, and obeys no natural laws)

The Nature-Nurture Debate

• The nature-nurture debate revolves around whether humans and other animals inherit their behavioral capacities or acquire them through learning.
• John B. Watson (nurture) argued that there is no evidence of inheritance of behavioral traits.
• Ethology (nature) emphasizes the role of genetics in shaping behavior.

Problems with Traditional Dichotomies

• Brain damage can impact psychological functioning, as seen in the case of asomatognosia (the man who fell out of bed).
• Chimps exhibit human-like psychological abilities, such as self-awareness and psychological complexity.
• Factors other than genetics and learning, such as fetal environment, nutrition, and stress, influence behavioral development.

Model of Biology of Behavior

• All behavior is the product of interactions among three factors:
  1. The organism's genetic endowment
  2. Experience
  3. Perception of the current situation

Human Evolution

• Modern biology began with Charles Darwin's publication of "On the Origin of Species" in 1859.
• Darwin suggested evolution through natural selection, where members of each species vary in their structure, physiology, and behavior.
• Evolution of vertebrates:
  • Complex multicellular water-dwelling organisms emerged 800 million years ago.
  • Chordates (animals with dorsal nerve cords) evolved 250 million years later.
  • Vertebrates (animals with spinal bones) evolved 25 million years later.
• Evolution of amphibians:
  • Bony fishes started to venture out of water 410 million years ago.
  • Fins and gills transformed into legs and lungs, leading to the evolution of amphibians 370 million years ago.
• Evolution of reptiles:
  • Reptiles evolved from a branch of amphibians 315 million years ago.
  • They developed shell-covered eggs and dry scales, reducing their reliance on watery habitats.
• Evolution of mammals:
  • A new class of vertebrates evolved from small reptile lines 225 million years ago.
  • Females nurture their young in a watery environment within their bodies until birth.
• Emergence of humankind:
  • Humans, known as hominins, evolved from Australopithecus around 4 million years ago.
  • Homo sapiens emerged 275,000 years ago.

Thinking about Human Evolution

• Evolution does not proceed in a single line.
• Humans have no reason to claim evolutionary supremacy.
• Evolution does not always proceed slowly; rapid changes can be triggered by sudden environmental changes.
• Fewer than 1% of all known species are still in existence.

Evolution of the Human Brain

• There is no clear relationship between overall brain size and intelligence.
• Brains have increased in size during evolution.
• The number of convolutions (folds on the cerebral surface) has greatly increased the surface area of the cerebral cortex.

Understanding Mate Bonding

• Most mate bonds are promiscuous.
• Most mammals form polygynous mating bonds.
• Polyandry is rare in mammals.
• Humans generally form monogamous bonds.
• Mate bonding in humans is predicted through evolutionary theory.

Fundamental Genetics

• Mendelian genetics:
  • Dichotomous traits occur in one form or another, but never in combination.
  • True breeding lines are breeding lines where interbred members always produce offspring with the same trait.
• Chromosomes:
  • Genes are located on chromosomes.
  • Humans have 23 pairs of chromosomes with an allele on each chromosome.
  • Meiosis (produce gametes) involves the division of chromosomes, and one of each pair goes to each of the two gametes.
  • Mitosis follows meiosis, doubling the number of chromosomes.

Structure and Replication

• Each chromosome is a double-stranded molecule of DNA.
• DNA replication involves the unwinding of two strands, and complementary bases attract each other.
• Clinical consequences of chromosome replication:
  • Down syndrome (extra chromosome)
  • Mutation (alterations of individual genes)

Sex Chromosomes and Sex-Linked Traits

• Sex chromosomes are X and Y.
• Sex-linked traits are influenced by genes on the sex chromosomes.
• Dominant traits on the X chromosome are seen more in females.
• Recessive traits are seen more in males.
• Color blindness is rare in females.

Genetic Code and Gene Expression

• Promoters: stretches of DNA that determine whether or not particular structural genes are converted into proteins.
• Activators: proteins that bind to DNA and increase gene expression.
• Repressors: proteins that bind to DNA and decrease gene expression.
• Gene expression involves two phases:
  1. Transcription: the conversion of DNA into mRNA.
  2. Translation: the conversion of mRNA into protein.
• Epigenetics: the study of mechanisms of inheritance other than those mediated by changes to the DNA sequence.

Human Genome Project

• The purpose of the Human Genome Project is to compile a map of the sequence of all 3 billion nucleotide bases that compose human chromosomes.
• Protein-encoding genes constitute only about 1% of human DNA.
• The Human Proteome: a nearly complete map of the entire set of proteins encoded by human genes.

Modern Genetics and the Growth of Epigenetics

• Epigenetics: the study of all mechanisms of inheritance other than those mediated by changes to the DNA sequence.
• Four factors that led to the rise of epigenetics:
  • The Human Genome Project generated an arsenal of new research techniques.
  • Protein-coding genes constitute only about 1% of human DNA.
  • Protein encoding is only a minor function of RNA.
  • The mechanism of gene-environment interaction is unknown.
• Five important advances in epigenetics:
  • Non-gene DNA is no longer accepted.
  • Variety of different types of small RNA molecules.
  • Gene expression can be regulated by DNA methylation, histone remodeling, and RNA editing.
  • Epigenetic mechanisms can be enduring.
  • Transgenerational epigenetics examines the transmission of experiences via epigenetic mechanisms across generations.

Epigenetics on Behavioral Development: Interaction of Genetic Factors and Experience

• Selective breeding of maze-bright and maze-dull rats:
  • Tyron's experiment showed that selective breeding based on one behavioral trait brings a host of other behavioral traits along with it.
  • Maze-dull rats made more errors only when reared in impoverished environments.
• Phenylketonuria (PKU): a single metabolic disorder:
  • Symptoms include vomiting, seizures, hyperactivity, irritability, and brain damage.
  • PKU homozygotes lack phenylalanine hydroxylase, leading to low levels of dopamine.
  • A phenylalanine-restricted diet can reduce the development of intellectual disability.
• Development of bird song:
  • Sensory phase: birds form memories of adult songs they hear, which guide the development of their own singing.
  • Sensorimotor phase: juvenile male birds develop their own songs through vocalizations and auditory feedback.
  • Most songbird species are age-limited learners, but some are open-ended learners.

This quiz explores the origins of dichotomous thinking, the influence of the church on Western culture, and the philosophy of Rene Descartes in the context of psychology and science.