Psychobio Theme 3-6 Key Concepts

1. Evolutionary views of evolutionism (theistic vs scientific)

Theistic evolution (Gradual Creation): God guides EVOLUTION — accepts old Earth & normal geology

Scientific (non-theistic) evolution: Natural causes only, independent of religious assumptions

Progressive Creationism: Reject or limit evolution, God created new forms of life gradually over a long period of time

Quick Creation (Young Earth Creationism): God created Earth & all living things in a short period of time (six 24-hour days — Book of Genesis)

2. Typological (essentialism) vs. Variational (Darwinian) thinking

Typological (Essentialism): Species have fixed “essences,” Change = imperfections (fixed “types” that species are categorized into)

Variational (Darwinian): Populations vary; natural selection acts on individuals’ variation —> evolution

Aristotle’s “Ladder of Nature” vs Darwin’s population thinking

3. Homologous vs. Analogous traits

Homologous: Similar due to Shared Ancestry (e.g. vertebrate forelimbs)

Analogous: Similar due to Convergent Evolution (e.g. bird vs bat wings)

4. Vestigial vs Atavistic traits 

Vestigial: inherited characteristic that has lost its original function over time (e.g., appendix, goosebumps)

Atavistic:  ancestral characteristic that reappears in an individual after being lost through evolution (e.g., human tail) (occur bc genes for lost trait are preserved in DNA —> can be expressed due to mutation, change in timing of gene expression, etc)

5. Facts & Inferences of Darwin’s Theory

Facts:

1. Superfecundity (produce more offspring than can survive)

2. Population Stability 

3. Limited Resources

4. Individual Variation

5. Heritability 

Inferences: 

1. Struggle for existence

2. Natural Selection

3. Evolution Over Generations

6. The six Hypotheses of Darwin’s Theory

1. Evolution Occurs

2. Common descent (all living things are related & descended from a single common ancestor)

3. Gradualism

4. Natural Selection

5. Speciation

6. Soft Inheritance (rejected later) (traits acquired during life, often due to environ factors, can be passed down to offspring — FALSE: only DNA sequence itself is passed on)

7. MES, PET, and EES theories

Modern Evolutionary Synthesis (MES): Evolution = allele frequency change + speciation; gradual; nat selec main mechanism

Punctuated Equilibrium Theory (PET): Long stasis punctuated by rapid change during speciation; emphasizes exaptation (trait for one function evolved to have a new role) and constraints 

Extended Evolutionary Synthesis (EES): Adds epigenetics, developmental bias (tendency for developmental processes to favor certain evolutionary outcomes —> non-random distribution of variation), phenotypic plasticity, niche construction, rejects strict gene-centricism (strict gene-centricism ignores environ, epigen, etc, says genes are primary unit of nat selec)

8. Why are our Bodies suboptimal 

• path dependence (historical contraints)

• mismatch with modern environs

• coevolution with pathogens

• trade-offs (e.g., immune defense (attacks pathogens) vs. autoimmunity (immune system attacks healthy tissues/cells)) (strong defense against pathogen can accidentally trigger autoimmunity)

• reproductive success often > health optimization

9. Mode & Tempo of Evolutionary Change

Anagenesis: gradual change within a lineage (phyletic evolution) (gradual evo of single lineage over time, leading to the replacement of the ancestral species w/new one)

Cladogenesis: splitting —> speciation ("branching evolution" where a single lineage splits into two or more new lineages, resulting in new species)

Stasis: little/no change

Gradualism: constant, slow evolution

Punctuationism: rapid change at speciation events

Microevolution: changes in allele frequencies

Macroevolution: origin of a new taxa above species level

11. Models of Speciation

1. Allopatric — GEOGRAPHIC isolation

   • Vicariance (symmetric), Peripatric (founder effect — small group)

2. Parapatric — contiguous population (geographically adjacent, but not fully separated)

3. Sympatric — within same area (due to diff niches, behavior, genetics)

12. Agents of Evolution

Mutation: creates variability

Migration (gene flow): increases similarity

Genetic Drift: random change in allele freq due to chance events, strong in small pops

Non-random mating: affects genotype freq

Natural Selection: NON-random, adaptive

13. Models of Natural Selection

Directional: favors one extreme

Stabilizing: favors average

Disruptive: favors both extremes

—> adaptation or speciation

14. Naturalistic Fallacy

Panglossianism (an unreasoningly extreme/naive optimism in the face of adversity)

• Mistaking “what is” for “what ought to be”

• Assuming natural = good

15. Aptation, Adaptation, Exaptation, Pre-aptation, Spandrel

Aptation: any trait increasing fitness (general)

ADAPtation: evolved by nat selection; original & current function match

EXAPtation: trait co-opted for new use (e.g., feathers for flight)

PRE-aptation: trait functional before being used for new purpose

Spandrel: by-product of evolution of another trait, later co-opted functionality 

16. Constraints on Adaptation

• Structural (allometry) — e.g., skull size limits

  • allometry: how characteristics of an organism change in relation to its body size

• Developmental (ontogenetic) — pleiotropy, epistasis

  • pleiotropy: expression of multiple traits by a single gene

  • epistasis: expression of one gene is modified (masked, inhibited, suppressed) by expression of one or more other genes

• Phylogenetic (historical) — e.g., recurrent laryngeal nerve

  • —> produce non-adaptations or maladaptations

17-19. Developmental Evolution

Preformationism: embryo preformed in sperm/egg

Epigenesis: organism develops through differentiation (from a simple, undifferentiated state (like a fertilized egg) —> new structure & organs)

Haeckel’s recapitulation: ontogeny (embryonic develop) repeats phylogeny (evolutionary history) 

Von Baer’s Law: development goes from general —> specific (general characters of a large group of animals appear earlier in their embryos than the more special characters)

Progenesis vs. Neoteny: accelerated (Pro) vs. delayed sexual maturity (Neo)

• Progenesis: organism reaches sexual maturity in a juvenile or larval stage, while still retaining juvenile physical characteristics

• Neoteny: retention of juvenile physical and behavioral traits in an adult organism

21-22. Grade vs. Clade Cladograms

Grade: level of structural/functional organization (paraphyletic group that includes a common ancestor but NOT all descendants, based on shared physical similarities rather than complete ancestry)

Clade: monophyletic group (ancestor + descendants)

Cladograms: use homologous, derived, shared (synapomorphic) traits

branching diagram that illustrates hypothetical evolutionary relationships btwn groups of organisms

23. Symbiogenesis

Primary: engulfing prokaryote —> mitochondria/chloroplast

Secondary/Tertiary: eukaryote engulfs another eukaryote

24-25. Gould’s Disparity, Diversity, and Contingency

Disparity: # of body plans (phyla)

Diversity: # of species

Early life = high disparity, later = high diversity

Predictability vs. Contingency: evolution is not directional; chance events shape outcomes

• Predicability: given similar starting conditions, nat selec guides pops to similar solutions, supported by patterns of convergent evolution

• Contingency: evo is largely unpredictable; historical accidents (like mutations) play a huge role in unique outcomes

26. Rejecting the Ladder of Progress

• Evolution ≠ progress toward “higher” beings

• Life adapts to environs, NOT toward perfection (Darwin, Gould)

28. Classifying Humans: Hierarchichalness and Embeddedness

Humans AREN’T classified as separate from other animals — we are embedded within the evolutionary hierarchy

• Hierarchichalness: Life is organized in nested groups (Domain —> Kindgom —> Phylum —> Class —> Order —> Family —> Genus —> Species)

• Embeddedness: Humans belong to each level: Eukarya —> Animalia —> Chrodata —> Mammalia —> Primates —> Hominidae —> Homo —> sapeins

• This classification reflects shared ancestry, not superiority or “progress” up a ladder 

  • Rejects “Great Chain of Being” idea

29. Diagnostic Features of the Primate Order

Primates share evolutionary traits shaped by arboreal (tree-living) life:

• grasping hands/feet with opposable thumbs (precision grip)

• nails instead of claws

• large brain relative to body size

• forward-facing eyes —> binocular vision —> depth perception (stereoscopic)

• reduced snout, increased reliance on vision over smell

• flexible shoulder joint and mobile limbs (for climbing & manipulation)

• sociality: complex social structures & long paternal carte

Humans evolved from these traits, NOT independently of them

30. Brain growth: Relative Prenatal & Postnatal Growth (Humans vs Nonhuman Primates)

• In nonhuman primates, brain growth slows after birth; body growth dominates

• In humans, brain growth continues at prenatal rates for 12 months post birth —> large brain at the expense of early independence

• —> altriciality (newborns req extensive care) and long dependency, but allows extended learning & plasticity

  • —> important for complex social behavior & culture

31. Obstetric Dilemma vs. Energetic Dilemma (timing of birth)

Two hypotheses explaining why human infants are born early & helpless

Obstetric Dilemma:

Birth timing balances large fetal brain vs. narrow pelvis (for bipedal locomotion) 

Mechanical constraint

Wider hips hinder efficient walking —> early birth before head too large

Energetic Dilemma: 

Birth timing constrained by metabolic limits of the mother

Energetic constraint

Gestation (time from conception to birth) ends when mother reaches max sustainable energy output

32. Primates & Encephalization Quotient (EQ)

EQ = observed brain size/expected brain size (for body wieght)

expected = baseline for mammals of same body size

Human EQ = 7 (7x larger than expected)

Chimp EQ = 2.5

EQ correlates with behavioral complexity, tool use, social cognition

33. Overcoming Energetic Constraints on Brain Evolution

Humans evolved strategies to meet energy demands of growing brain

1. Bipedality: free hands for tool use & efficient long-distant travel

2. Dietary Shift: more meat (high caloric density) + aquatic foods (omega-3 fatty acids for brain cell development, etc)

3. Cooking: heat/fire based cooking —> softens food —> reduces chewing —> increases caloric intake

4. Social foraging & food sharing: cooperative energy access supports costly brain tissue

Higher caloric efficiency allowed brain explansion (encephalization) w/out starving other organs

34. Human Evolution: Evolutionary Transitions (Grades), Tree, Timeline

Key Evolutionary Grades (successive stages w/major anatomical & behavioral shifts)

First Hominins: Sahelanthropus, earliest bipedality, small brain (365cc)

Archaic Hominins: Australopithecus, habitual bipedality, small canines, 460cc

Megadont Archaic Hominins: Australo, heavy jaws, robust skull

Transitional Hominins, H. Habilis, first tools, larger brain 600-700cc

Premodern Homo: H. erectus, H. neanderthalensis, fire, tools, migration, large brains 800-1400cc

Modern Homo: H. sapiens, symbolic thought, language, art, cultural complexity, 1426cc

26. Origin of Anatomically Modern Humans

Two Main Hypotheses:

1. Multiregional: H. erectus spread from Africa —> regional evolution into H. sapiens 

   • Continuous gene flow

   • Evidence: fossil continuity, minor genetic overlap

2. Out-of-Africa: H. sapiens evolved in Africa then replaced archaic humans in other continents

   • NO gene flow (complete replacement)

   • Evidence: strong genetic, mitochondrial, fossil support

Modern Consensus: Modified Out-of-Africa (some interbreeding w/neandethals & Denisovans)

37. Uniqueness of Modern Humans: Neanderthal vs. Sapiens

Neanderthal: extinct species of archaic human, coexisted & interbred with modern humans for a sec, large brains, culturally sophisticated; tools, clothes, art

Cranial Capacity:

Neo = 1450cc (modern human)

H. Sapiens = 1350-1450 cc

Skull Shape: 

Neo = long, low cranium, prominent row ridge

H. Sap = rounded, small brow ridge

Face: 

Neo = projecting midface, large nose

H. Sap = flat face, small jaw/chin

Culture:

Neo = burials, tools

H. Sap = art, complex symbolism, language

Genetic Relation: 

Neo = 1-4% of non-African DNA shared

H. Sap = result of ancient mixture

38. Human vs. Chimp Genomes & Phenomes

Molecular Level:

• Chromosomal: Human chromosome 2 was made from fusion of two ancestral ape chromos

• Regulatory: greater gene reg in human brain —> expanded cerebral cortex devel

• Transposable Elements: more active in humans (incr genetic plasticity)

• Y-chromosome: highly divergent; gene loss & rearrangements in humans but chimps have lost more genes

Phenomic Level:

• Humans: bipedality, language, social complexity, longer lifespan, extended childhood

39. Evolution of Hairlessness, Pigmentation, Body Size & Shape

Hairlessness: evolved for thermoregulation (heat dissipation)

Sweating: incr eccrine glands —> endurance running

Skin Pigmentation:

• Dark skin: protects folate (from UV damage)

• Light skin: allows vitamin D synthesis in low UV zones

• Trade-off: latitude correlated w/pigmentation

Body Shape: Bergmann & Allen’s rules: colder climates —> compact body, warmer —> elongated limbs

40. Balancing Natural Selection & Human Disease

Some harmful alleles persist bc of the heterozygous benefit:

HbS: sickle-cell disease — but allele protects against malaria

HFE: Hemochromatosis — but protects against plague, anemia

CFTR: cystic fibrosis — but cholera, diarrhea

G6PD: favism — but malaria

ALDH2: alcohol flush — but alcoholism

Balancing Selection maintains polymorphisms (many forms) under region-specific pressures

41. Pathogen Age & Human Mortality

• Ancient pathogens (e.g., herpes, tuberculosis): long coevolution —> lower virulence

• Recent pathogens (e.g., HIV, Ebola): no long adaptation —> high mortality

—> over time, pathogens & hosts tend to evolve mutual tolerance 

42. Consequences of Meat-Eating & Cooking

Nutritional: concentrated calories —> supports high metabolic rate of brain

Biological: reduced gut volume, smaller teeth & jaw, shorter intestines

Social: cooperation, food sharing, division of labor, fire control

Cognitive: freed time for socialization & cultural development

Paradoxes of Human Life History Patterns

Humans exhibit unique combos among mammals:

• Long lifespan

• Late maturity but short interbirth intervals

• Long childhood & adolescence (—> social learning, skills)

• Extended grandparent investment (promotes survival of offspring)

• Trade-offs: reproduction vs. longevity, growth vs. maintenance

New/Expanded Concepts From Notes

1. Horizontal Gene Transfer & Web of Life (Theme 3)

Evolution is NOT strictly tree-like — Horizontal transfer of genetic info btwn species (esp in early pro and eukaryotes) creates a web of life

—> Shows gene flow across species is part of major evolutionary transitions

2. Transmutationism vs. Transformationism

Transmutationism (Saltationism): Evolution by sudden, major mutations 

Transformationism (Uniformitarianism): Gradual accumulation of small changes; continuity btwn past & present species 

(historical precursors to Darwin’s Gradualism)

3. Coevolution & Arms Race 

Mutualism (both benefit) — Commensalism (one benefits) — Parasitism — Competition

“kleptoparasitism” = stealing resources

parasite manipulation of host behavior

4. Court Jester vs. Red Queen Hypothesis (theme 5)

Red Queen: (ongoing selection)

Driver of Evolution: biotic factors (coevolution, competition, arms race)

Scale: local, short term (microevolution)

Pattern: continuous (“run to stay in place”)

Court Jester: (mass extinctions!)

Diver of Evolution: Abiotic factors (climate, plate tectonics, catastrophies)

Scale: global, long-term (macroevolution)

Pattern: punctuated, unpredictable events

5. Adaptive Radiation & Extinction Models

Adaptive Radiation: rapid diversification after colonizing empty niches

Mechanisms:

• colonization of new niches

• competitive replacement (biotic)

• independent/passive replacement (abiotic)

Extinction models

• TUG (Turning Up the Gain) — natural selection dominance

• Random — chance survival

• Different Rules — preadaptation/spandrels confer survival

4 Mechanisms of Developmental Evolution

Under the modern view (heterochrony):

Heterotopy: change in location of developmental process

Heterochrony: change in timing of development (—> progenesis, neoteny)

Heterometry: change in amount of gene expression

Heterokairy: change in kind or order of development

7. Phylogeny Types & Grades vs Clade (with examples)

Monophyletic: ancestor + ALL descendants 

Paraphyletic: ancestor + SOME descendants

Polyphyletic: unrelated species with similar traits (e.g., “marine mammals” as a grade)

Adaptive Radiation + Cambrian Explosion

• Disparity (body plans) peaked early, Diversity (# species) later

• Ediacaran and Tomotian faunas = failed experiemnts —> succeeded w/ Burgess Shale fauna

Maynard-Smith, Benton, Cavalier-Smith

Authors & their focus:

Maynard-Smith: unique, only-once evolutionary innovations (e.g., DNA, sex, eukaryotes)

Benton: focus on biological innovations & ecological colonization events

Cavalier-Smith: Early cellular transition pre-multicellularity

10. Foyle and Gamble’s Model of Human Social Transitions

Key evolutionary trends in human society: 

1. Community: maintaining cohesion despite fission-fusion group structure

   • groups regularly split (fission) and merge (fusion)

2. Kinship: foundation of cooperation and alliances

3. Social identity: cognitive and symbolic evolution

4. Ecological autonomy: resource control and territoriality

ABO Blood System & Disease

• A/B alleles = advantage in bacterial environments; O = viral resistance

• RH incompatibility = maternal-fetal conflict

Life History Trade-offs

High mortality —> fast life history 9early repro, short life)

Low mortality —> slow (delayed reproduction, long life)

Cooking/fire —> decr mortality —> slow life evo (long childhood, longevity)