Evolution, Genetics, and Environment PDF

Evolution, Genetics, and Experience Outline Biology of Behavior-related thoughts: From dichotomies to interactions Evolution of Human Fundamental Genetics Behavioral Development: Interaction of Genetic Factors and Experience Genetics of Human Psychological Differences Nature of...

Evolution, Genetics, and Experience Outline Biology of Behavior-related thoughts: From dichotomies to interactions Evolution of Human Fundamental Genetics Behavioral Development: Interaction of Genetic Factors and Experience Genetics of Human Psychological Differences Nature of human behavior Is it physiological vs. psychological? or inherited vs. learned behavior? To align our understanding with modern biopsychological science, which recognizes the interplay between biology, environment, and behavior. Physiological or psychological? In Western cultures, it rose to prominence following the Dark Ages, in response to a 17th-century conflict between science and the Roman Church Rene Descartes argued that the universe is composed of two elements: (1) physical matter, which behaves according to the laws of nature and is thus a suitable object of scientific investigation; and (2) the human mind (soul, self, or spirit), which lacks physical substance, controls human behavior, obeys no natural laws, and is thus the appropriate purview of the Church. The human body, including the brain, was assumed to be entirely physical, and so were nonhuman animals. Physiological or psychological? Cartesian dualism, as Descartes’s philosophy became known, was sanctioned by the Roman Church, and so the idea that the human brain and the mind are separate entities became even more widely accepted. Most people now understand that human behavior has a physiological basis, but many still cling to the dualistic assumption that there is a category of human activity that somehow transcends the human brain (Demertzi et al., 2009) Behavioral Development: Inherited or learned? Early North American experimental psychologists, like John B. Watson, strongly supported the nurture side. Watson believed that upbringing and environment could shape any healthy infant into any profession or role, regardless of inherited traits. European ethologists studied animals in the wild, emphasizing instinctive behaviors that seemed inherited, not learned. They believed these behaviors were entirely a product of nature. Physiological-or-Psychological Two main lines of evidence challenging the idea that complex psychological functions cannot stem from the physical brain. Brain Damage and Psychological Changes Psychological Complexity in Non-Humans Physiological-or-Psychological Brain Damage and Psychological Changes For example, asomatognosia, a condition where a person loses awareness of part of their own body, often results from damage to the brain's right parietal lobe. Physiological-or-Psychological Psychological Complexity in Non- Humans Research shows that some non- human animals, like chimpanzees, exhibit self-awareness and psychological complexity, once thought to be exclusively human. Nature or Nurture Initially, people believed that behavior was shaped by either genetics (nature) or learning (nurture). Later, it was expanded to include other experiential factors like the fetal environment, nutrition, stress, and sensory stimulation, broadening "nurture" to mean "experience.“ It's not about asking "how much" each contributes, but rather understanding how they work together—just like how a musician and their instrument interact to produce music. Model of Behavior 1.Genetic endowment, shaped by evolution. 2.Experience, including all environmental influences. 3.Perception of the current situation. Darwin’s Theory of Evolution: Published in 1859 by Charles Darwin in On the Origin of Species. Fossil records show gradual changes over time. Similar structures in different species (e.g., human hands and bird wings) suggest a common ancestor. Selective breeding in domestic animals and plants demonstrates evolutionary change. Direct observation, like Darwin’s finches evolving after a drought. Natural Selection: Traits that help survival and reproduction are passed down. Over generations, this leads to species better adapted to their environment. Darwin compared this to selective breeding in animals. Fitness: An organism’s ability to survive and pass on genes. Darwin’s Theory of Evolution Published in 1859 by Charles Darwin in On the Origin of Species. Fossil records show gradual changes over time. Similar structures in different species (e.g., human hands and bird wings) suggest a common ancestor. Selective breeding in domestic animals and plants demonstrates evolutionary change. Direct observation, like Darwin’s finches evolving after a drought. Natural Selection: Traits that help survival and reproduction are passed down. Over generations, this leads to species better adapted to their environment. Darwin compared this to selective breeding in animals. Fitness: An organism’s ability to survive and pass on genes. Evolution and Behavior Evolution is a crucial concept with abundant evidence from various sources, including museums, books, and scientific studies. It's a well- supported theory with practical implications for medicine and our understanding of life. 1.Obvious Behaviors: Actions like finding food, avoiding predators, and protecting offspring directly enhance an animal's chances of passing on its genes. 2.Less Obvious Behaviors: Behaviors such as social dominance and courtship displays also play a key role in evolution. Evolution and Behavior Social Dominance: Many species establish social hierarchies through combat or displays. Dominant males usually win against other males, while lower-ranking males submit to higher-ranking ones. Dominant males often have more mating opportunities, thus passing on their genes more frequently. For example, dominant bull elephant seals copulate far more than lower-ranking males. Female Dominance: In some species, dominant females produce more and healthier offspring. For instance, high-ranking female chimpanzees have more surviving offspring due to better access to food resources. Courtship Display and Evolution of Species Courtship Displays: Before mating, many species engage in a series of signals (olfactory, visual, auditory, or tactual). Both the male and female respond to each other's signals, and mating happens only when both react appropriately. Courtship Display and Evolution of Species Species-is a group that can produce fertile offspring by mating only with its own members. Formation of New Species: A new species emerges when a subgroup becomes reproductively isolated and evolves separately. This isolation can be due to geographic or behavioral barriers. Behavioral Reproductive Barriers: Variations in courtship displays can create reproductive barriers, preventing mating with the original population, eventually leading to the development of a new species. Evolution of Vertebrates Complex multicellular organisms first appeared in water. Chordates: Evolved 450 million years ago, animals with a dorsal nerve cord. Vertebrates: Chordates with spinal bones, first seen in bony fish (~425 million years ago). Today, vertebrates include fish, amphibians, reptiles, birds, and mammals.  Evolution of Amphibians 410 million years ago: Bony fish began venturing onto land. Natural selection led to evolution of legs and lungs from fins and gills. Amphibians (frogs, toads, salamanders) evolved and can live on land as adults but need water for their larval stage. Evolution of Reptiles 300 million years ago: Reptiles evolved from amphibians. Adapted to live on land: shell-covered eggs and dry scales helped reduce water dependence. Examples: Lizards, snakes, turtles. Evolution of Mammals 180 million years ago: Mammals evolved from small reptiles. Key adaptation: Mammary glands to feed young. Egg-laying stopped: Mammals began nurturing offspring inside their bodies. Example: Duck-billed platypus still lays eggs. Emergence of Primates Humans belong to the order Primates, which evolved from small, tree-dwelling animals. Opposable thumbs and long arms for treetop travel. Apes (e.g., chimpanzees, gorillas) evolved from Old-World monkeys. Chimpanzees share 99% of genes with humans. Emergence of Hominins Hominins include two genera: Australopithecus and Homo. Australopithecus lived 6 million years ago, walked upright. Homo species evolved 2 million years ago, used tools and fire. Modern humans (Homo sapiens) appeared 200,000 years ago in Africa, migrating out around 50,000 years ago. Thinking About Human Evolution Evolution is not a single line: It's more like a dense bush with many branches, not a ladder or scale. We are one of the last surviving species from a family that has existed for a short time. Evolution can be rapid: It doesn't always proceed slowly. Environmental changes or genetic mutations can trigger quick evolution. Thinking About Human Evolution Most species didn’t survive: Less than 1% of species have made it to the present day. Evolution. It adapts existing features, often resulting in imperfect solutions (e.g., the human scrotum for sperm temperature regulation). Non-adaptive by-products exist: Some traits are spandrels—by- products of evolution that serve no adaptive purpose (e.g., belly button). Thinking About Human Evolution Exaptations: Traits that evolved for one function but were later co- opted for another (e.g., bird wings evolved from limbs for walking). Similarities are not always due to shared origins: Homologous structures share a common ancestor (e.g., bird wings and human arms). Analogous structures evolved independently to solve similar problems (e.g., bird wings and bee wings). Evolution of the Human Brain Brain size is not directly related to intelligence: Whales and elephants have larger brains than humans. Famous intellectuals, like Einstein, had unremarkable brain sizes. Evolution of the Human Brain Brain size relative to body weight: Humans rank higher in brain-to-body ratio (2.33%) than elephants (0.20%). However, some smaller animals, like the shrew (3.33%), surpass humans in this ratio. Evolution of the Human Brain Evolution of different brain regions: Brain stem: Controls basic survival functions (e.g., heart rate, breathing). Cerebrum: Manages complex processes like learning, perception, and motivation. Key changes in brain evolution: Brain size has increased, especially in the cerebrum. Convolutions (folds) on the cerebral surface increased the surface area of the cerebral cortex (important for complex functions). Evolution of the Human Brain Similarities across species: Human brains share basic structures and connections with other species, like monkeys and mice. Evolutionary Psychology and Mate Bonding Evolutionary Psychology focuses on understanding behaviors through evolutionary pressures. Mate Bonding: Promiscuity: Common in many species. Mating Bonds: More common in mammals due to the need for parental care of helpless offspring. Polygyny: One male, many females. Evolved due to females' high investment in reproduction and males' ability to sire many offspring. Evolutionary Psychology and Mate Bonding Polyandry: One female, many males. Occurs when males provide more parental care (e.g., sea horses). Monogamy: One male, one female. Evolved when females benefit from exclusive male support to raise more fit offspring. FUN-DAMENTAL GENETICS SHORT ACTIVITY In pairs, imagine you each inherited a "genetic superpower" (e.g., super strength, incredible memory, extra-fast reflexes). Take 2 minutes each to share what your superpower would be and which parent you think you got it from. Quickly discuss if this "superpower" could be influenced by genetics or the environment. FUNDAMENTAL GENETICS Mendel studied inheritance in pea plants and discovered how traits are passed through dominant and recessive genes. Dichotomous Traits: Traits appear in one form or another (e.g., brown vs. white seeds). Offspring from true-breeding lines always show the same trait. Phenotype vs. Genotype: Phenotype is the observable trait; genotype is the genetic makeup that determines the trait. Alleles: Organisms have two alleles for each trait; homozygous means two identical alleles, heterozygous means two different alleles. Chromosomes: Reproduction & Recombination Genes are located on chromosomes, which come in matched pairs (humans have 23 pairs). Meiosis: Cell division that produces gametes (sperm and egg), where each gamete gets half the chromosomes (23). Fertilization: A zygote forms when a sperm and egg combine, restoring the full 46 chromosomes. Chromosomes: Reproduction & Recombination Genetic Recombination: During meiosis, chromosomes cross over, creating genetic diversity. Mitosis: Regular cell division where the chromosome number doubles to maintain the full set of chromosomes in new cells. Mitosis vs. Meiosis Mitosis: To make identical copies of cells. How it Works: A cell splits into two new cells, each with the same number of chromosomes as the original cell. Result: Two identical cells. Meiosis: To produce reproductive cells (egg and sperm) with half the number of chromosomes. How it Works: A cell splits twice, producing four new cells, each with half the chromosomes of the original cell. Result: Four unique cells with half the chromosome number, ready for reproduction. Chromosome: Structure and Replication DNA is a double-stranded molecule with four nucleotide bases: adenine (A), thymine (T), guanine (G), and cytosine (C). A pairs with T and G pairs with C. Strands are complementary. DNA Replication: DNA unwinds and each strand is used as a template to create two identical DNA molecules. Chromosome: Structure and Replication Chromosomes come in pairs; humans have 23 pairs. Meiosis produces gametes with half the chromosome number (23). Genetic recombination during meiosis increases diversity. Sex chromosomes (X and Y) determine sex. X-linked traits can be recessive and more common in males (e.g., color blindness). Chromosome: Structure and Replication Gene expression involves genes coding for proteins, regulated by enhancers, through two phases: transcription (DNA to RNA) and translation (RNA to protein). Epigenetics of Behavioral Development: Interaction of Genetic Factors & Experience "A child shows a strong aptitude for music (genetic potential), but their musical development depends on the availability of instruments and lessons (environment).“ QUESTION: How does the genetic potential interact with the environment to shape the child's cognitive development?What happens if the environmental factors are less supportive? Epigenetics of Behavioral Development: Interaction of Genetic Factors & Experience Ontogeny is the development of individuals over their life span; Phylogeny, in contrast, is the evolutionary development of species through the ages SELECTIVE BREEDING OF “MAZE-BRIGHT” AND “MAZE-DULL” RATS Tryon's 1934 experiment showed that maze-running ability in rats is inherited, not learned, as maze-bright rats consistently performed better even when reared by maze-dull parents. Cross-Fostering Control: Maze-bright offspring performed well even when reared by maze-dull parents, and vice versa, ruling out learned behavior as a factor. SELECTIVE BREEDING OF “MAZE-BRIGHT” AND “MAZE-DULL” RATS Behavioral Traits and Breeding: Multiple Traits: Selective breeding for one trait often affects other traits as well. Maze-Bright Traits: Maze-bright rats showed less fearfulness, not just better maze performance. Interaction with Environment: Cooper and Zubek Study (1958): Maze-dull rats in enriched environments performed better than those in impoverished environments, showing the influence of experience. PHENYLKETONURIA: A SINGLE-GENE METABOLIC DISORDER Discovery: In 1934, Asbjörn Fölling identified PKU in children with a distinctive urine odor. Symptoms—are mental retardation, vomiting, seizures, hyperactivity, irritability, and brain damage. PKU is caused by a recessive gene mutation. Both parents must carry the gene for a child to develop PKU. It affects about 1 in 10,000 white infants. PKU individuals lack an enzyme needed to convert phenylalanine to tyrosine, leading to brain development issues due to high phenylalanine levels and low dopamine. PHENYLKETONURIA: A SINGLE-GENE METABOLIC DISORDER Treatment: Newborns are screened for high phenylalanine levels. A phenylalanine-restricted diet can prevent severe mental retardation if started early, though subtle cognitive deficits may still occur. Early diet intervention is crucial; effects are less significant if treatment begins later. Genetics of Human Psychological Differences Development of individuals vs. development of differences among individuals Minnesota study of twins reared apart A look into the future: two kinds of twin studies Development of individuals vs. development of differences among individuals Development of Individuals: Interaction of genes and experience is inseparable. Differences Among Individuals: Genes and experience are separable. Musician Metaphor: Individual performance is a mix of the musician and the instrument. Differences in performance among many musicians can be statistically assessed to understand the impact of individual skill vs. instrument quality. Development of individuals vs. development of differences among individuals Development of Individuals: Interaction of genes and experience is inseparable. Differences Among Individuals: Genes and experience are separable. Behavioral Genetics: Studies use genetic similarity to determine the contribution of genes vs. experience. Example: Monozygotic twins (identical) vs. dizygotic twins (fraternal) to measure genetic vs. experiential effects. Minnesota Study of Twins Reared Apart: Extensive research on genetic and environmental influences. Minnesota study of twins reared apart Participants: 59 pairs of monozygotic (identical) and 47 pairs of dizygotic (fraternal) twins, ages 19-68. Method: 50 hours of testing on intelligence and personality. Findings: Monozygotic twins showed greater similarity than dizygotic twins on psychological dimensions, regardless of rearing environment. Definition: Quantifies the proportion of trait variability due to genetic variation in a study. Purpose: Indicates genetic contribution to differences among participants, not individual development. Limitations: Depends on genetic and environmental variation in the study. For instance, the Minnesota Study had low environmental variation. Minnesota study of twins reared apart Heritability in Traits: Estimates for traits like intelligence, personality, aggression, etc., range from 40% to 80%. Despite substantial heritability, some geneticists question the need for more heritability studies. A look into the future: two kinds of twin studies Epigenetic Effects in Twin Studies: Purpose: Explore how epigenetic changes (modifications in gene expression) are influenced by experience and can persist across generations. Method: Compare monozygotic (identical) twins to detect epigenetic differences. Findings: Monozygotic twins show epigenetic differences with age. Epigenetic changes can be influenced by experiences, not just genetics. Studies suggest that epigenetic differences may explain why one twin develops a disease while the other does not. A look into the future: two kinds of twin studies Effects of Experience on Heritability: Study by Turkheimer et al. (2003): Found that heritability of intelligence is lower in low-SES families compared to higher-SES families. Heritability estimates depend on environmental conditions. Implications: Intelligence development involves both genetics and environment. Programs to reduce poverty may help realize genetic potential.