BIOL300 Evolution Notes

Human Evolution

Homo Sapiens History

  • Out of Africa: H. sapiens migrated out of Africa approximately 60,000-70,000 years ago, rapidly spreading throughout Eurasia and Africa.
  • Ice Age Dispersal: Lowered sea levels during the Ice Age facilitated human dispersal into Sahul (New Guinea, Australia, Tasmania) around 50,000 years ago.
    • This marked only the third invasion of Sahul by placental mammals (bats and rodents).

Wallace’s Line

  • Definition: Wallace’s Line, identified by Wallace, denotes significant faunal differences across islands.
    • Example: Placentals vs. marsupials.
    • Example: Rainforest vs. eucalyptus and acacia vegetation.
  • Geological Significance: A deep oceanic trench existed during the Ice Ages along this line.
  • Seafaring Requirement: Humans likely needed watercraft to cross this line.
    • Evidence of early seafaring is challenging to find.

Beringia

  • Land Bridge: Beringia was a land bridge connecting Siberia and Alaska, existing from 26,000-19,000 years ago.
  • Beringian Standstill: H. sapiens migrated into Alaska, remaining there for thousands of years.
  • Alaskan Environment: Alaska was relatively ice-free, characterized by a dry, cold desert environment.
  • Movement South: Migration southward occurred through corridors or along the coast between 18,000-15,000 years ago.

Clovis People

  • Time Period: Existed around 13,000 years ago throughout North America.
  • Location: Named after Clovis, New Mexico.
  • Technological Tradition: Known for Clovis points, indicating shared technological traditions.
  • Lifestyle: Followed megafauna (ice age mammals).
  • Legacy: Developed into subsequent North American peoples.

South America

  • Monte Verde, Chile: Site dating back to ~14,000 years ago.
    • Evidence includes wood structures (huts), fire pits, and stone tools.
    • Pre-dates Clovis people in North America.
  • Other Coastal Sites: Found in Peru and Brazil.
  • Origin Theory: Possible migration from Australia/New Guinea.
    • Suggests multiple waves of H. sapiens into the New World.
  • Genetic Evidence: Limited early genetic evidence indicates a relationship with North American peoples.
  • Rapid Expansion: Migration from Alaska to Chile occurred within a few thousand years.

Kelp Highway Hypothesis

  • Definition: A proposed Pacific coastal route along Asia, Alaska, and the West Coast of the Americas.
  • Resources: Rich in sea life (fish, sea mammals, seaweeds).
  • Seafaring Skills: Evidence of seafaring skills in Asiatic peoples.
  • Open Routes: Coastal routes open around 18,000-17,000 years ago.
  • Submerged Sites: Many coastal sites are now underwater.
  • Explanation: Explains early sites as far south as Chile.

Evolutionary Innovations Leading to Humans

  • We are the sum of key evolutionary innovations in our ancestors:
    • Origin of Life: 3500 million years ago.
    • Mitochondrial Symbiosis: 2000 million years ago.
    • Multicellularity: 1000 million years ago.
    • Nerves and Muscle: 650 million years ago.
    • Dorsal Nerve Cord: 550 million years ago.
    • Bone: 500 million years ago.
    • Legs: 370 million years ago.
    • Amniotic Egg: 350 million years ago.
    • Placenta: 150 million years ago.
    • Binocular Vision: 70 million years ago.
    • Tail Lost: 18 million years ago.
    • Bipedalism: 4 million years ago.

Cultural Evolution

  • Nature vs. Nurture: Interaction of genetics and culture.
  • Human Learning Ability: Humans are genetically predisposed to learning.
    • Simple Learning: Trial and error, habituation (common in many animals).
    • Social Learning: Observation, imitation (e.g., chimps and early humans).
    • Cumulative Culture: Building on knowledge learned by others (e.g., H. erectus and H. sapiens).
  • Cultural Progression: Tool complexity increases over time.
  • Language: Used to share knowledge.
  • Teaching: Intentional transfer of knowledge.
  • Knowledge Accumulation: Learn socially, accumulate knowledge across generations, and innovate.

Ideas as Alleles

  • Analogy: Ideas are conceptualized as analogous to alleles in populations:
    • Variation:
      • Alleles: Different versions of a gene (e.g., blue eyes vs. brown eyes).
      • Ideas: Different versions of a concept (e.g., multiple ways to cook rice or solve a problem).
    • Fitness:
      • Alleles: Some alleles confer higher fitness if they improve survivability and reproduction.
      • Ideas: Some ideas confer higher fitness on individuals, too.
    • Inheritance:
      • Alleles: Passed through reproduction.
      • Ideas: Passed through communication, teaching, or imitation (cultural transmission).
    • Selection:
      • Alleles: Some are favored by natural selection if they improve survival or reproduction.
      • Ideas: Some are favored socially or culturally if they are useful, persuasive, or appealing.
    • Mutation:
      • Alleles: Can mutate randomly, introducing new traits.
      • Ideas: Can be created or modified intentionally or accidentally.
    • Drift:
      • Alleles: Even deleterious alleles can increase in frequency.
      • Ideas: Even bad or useless ideas can increase in frequency.
    • Population Dynamics:
      • Alleles and Ideas: Frequencies change over time in populations, spread across generations or populations.

Control of Fire

  • Homo erectus:
    • Evidence suggests control of fire around 2 million years ago, including charred bones and heated hearth stones (indirect evidence).
    • Clear hearth activity and repeated fire use at sites by 1.5 million years ago.
  • Significance:
    • Warmth: Enabled habitation in cold regions.
    • Cooking:
      • Allowed for denaturing of plant and animal proteins for easier digestion.
      • Reduced time needed for feeding.
      • Reduced chewing effort and dental wear.
      • Helped sterilize parasites and protect against infectious diseases.
    • Social Bonds: Gathering of individuals, increased social bonds, cooperation, and communication.
    • Agriculture and Civilization:
      • Burning to clear and enrich land for farming.
      • Permanent heat for cooking and warmth.
      • Fire in ritual and rites.

Tool Use

  • Definition: Tool - an unattached object used to purposefully perform a task to alter the environment or the animal’s condition.
    • Examples of what are NOT tools: using claws to dig, building a dam (e.g. beavers), or accidentally moving an object.
    • Weapons, too.
  • Other Animals:
    • Other primates and various animals use existing objects as tools; some of this is learned behavior.
    • Some modification of objects (e.g., crows bending twigs).
    • Chimps have a wide variety of tool use passed on by learning.

Tool/Weapon Use - Timeline

  • Early Homo/Late Australopithecus afarensis:
    • Stone tools, modified for cutting meat and plant material.
  • Oldowan Tools (Homo habilis):
    • 2.6 million years ago.
    • Simple flakes.
  • Acheulean Tools (Homo erectus):
    • 1.7 million years ago.
    • Hand axes, cleavers, symmetrical tools.
    • Suggests advanced learning and teaching.
  • Mousterian Tools (Homo sapiens, H. neanderthalensis):
    • 300,000 years ago.
    • Attaching points to handles, refined tools.
  • Paleolithic Tools (Homo sapiens):
    • 50,000 years ago.
    • Wide range of tools, refinement of techniques.
    • Points, fishhooks, blades of various kinds.

Tool/Weapon Use - Impact of Selection

  • Larger Brains: Selection pressure for problem-solving, planning, and memory.
  • Dexterity in Hands: Precision grip, use of fingers and thumb (flexor pollicis longus muscle).
  • Neurology: Neurology to control grip.
  • Food Processing: Tool-assisted diet led to smaller jaws and teeth.
  • Language: Communication of knowledge of tool use and creation.
  • Social Structure: Differing roles based on tool use, creation. Language and communication about tool technology facilitated social group cohesion.
  • Feedback Loop: Tool use created a selection feedback loop, influencing future selections.

Weapons - Shift in Power Balance

  • Early Humans:
    • Use of rocks, clubs.
  • Homo erectus (by 1.8 million years ago):
    • Use of throwing points, likely for both hunting and conflict.
    • Safer hunting and conflict due to distance from animal or enemy.
    • Even weaker individuals could use weapons effectively, shifting the power balance.
  • Impact:
    • May have selected for negotiation and language skills.
    • Regulation of norms (morality).
    • Trust.

Shelter

  • Paleolithic and Before:
    • Natural shelter (caves, etc.).
    • Simple created shelters with branches, leaves, hides, bones (portable).
  • Neolithic Revolution (~10,000 years ago):
    • Permanent settlements using mud, brick, wood, stone.
    • Associated with agriculture.

Clothing

  • Functions: Protection, thermoregulation, social expression.
  • Correlation with Hair Loss:
    • Australopithecus and H. habilis likely shaggy.
    • H. erectus and onward, less body hair.
    • Naked skin + sweating allowed for better thermoregulation in hot environments.
    • Fewer lice and ticks?
  • Development:
    • Simple animal hide or fiber clothing protected from the elements and allowed for life in cold climates (wraps, tunics, etc.).
    • As clothing was worn, selection for body hair was lessened.
  • Lice Divergence: Divergence of head lice and body lice around 170,000 years ago.

Retention of Body Hair

  • Head Hair:
    • Thermoregulation.
    • Protection from the sun.
    • Eventually, social and sexual signaling.
  • Facial Hair (Males):
    • Signaling social dominance, maturity, and status.
  • Lashes and Brows:
    • Protection of eyes.
    • Redirection of sweat and rain?
    • Social communication?
  • Pits and Pubes:
    • Pheromone dispersal.

Skin Color

  • Hair Loss Impact: Hair loss exposed skin.
  • Pigmentation: Skin pigmentation protects against UV radiation (DNA damage and cancers).
  • Adaptation to Northern Climates: As humans moved north, lighter skin was likely selected to improve Vitamin D production.
  • Multiple Alleles: Multiple alleles are involved in skin color determination.

Agriculture

  • Early Hominids: Hunter/gatherer lifestyle.
  • Neolithic Revolution (10,000-12,000 years ago):
    • Before: Fruits, nuts, hunted and scavenged animals.
    • After: Carbohydrate-heavy diets (e.g., wheat, rice, maize, potato).

Animal Agriculture

  • Neolithic Revolution: Followed plant agriculture and settlements.
  • Domestication: Domestication for food, labor, hides, etc.
  • Global Occurrence: Occurred throughout the world.
  • Species Selection: Centered on species that were more easily tamed (often social species).

Lactase Persistence

  • Gene-Culture Coevolution:
  • Lactose Tolerance: Persistence of lactose tolerance into adulthood conferred by mutation in the gene (LCT) regulating the lactase enzyme.
  • Mutation Timing: Mutation occurred 7500 years ago in central Europe (~375 generations ago).
  • Selection Pressure: Selected individuals who likely drank milk from domestic mammals (camels, horses, sheep, goats, cattle, reindeer) to survive during famines, providing a nutritional advantage.

Agriculture - Benefits

  • Cooperative Food Sources: More calories, collective effort, storage of food.
  • Permanent Settlements: Villages, towns, cities.
  • Social Hierarchies: Property, government.
  • Division of Labor: Surplus calories led to non-food gathering roles (toolmaking, construction, administration, religion).
  • Recordkeeping: Communication of agricultural practices may have led to written language.

Agriculture - Costs

  • Disease Exposure:
    • Zoonotic diseases due to proximity of livestock (e.g., tuberculosis, influenza).
    • Proximity of more people.
    • Epidemics lead to evolutionary pressure for improved immune systems.
  • Famine: Overreliance on single food sources and inability to move to seek resources.
    • Crop failure.
    • Soil degradation and overuse.
    • Climate events.
  • Social Stratification: Control of food sources by few individuals.
  • War: Conflict over regions, resources.
  • Nutritional Deficiency: Imbalanced diets.

Agriculture - Land Use Changes

  • Cutting and burning of forests.
  • Clearing of land.
  • Irrigation.
  • Human shaping of ecosystems.

Role of Technology

  • Niche Construction: Technology allows shaping of the environment instead of simply responding to it.
  • Examples: Building shelters, clothing, construction of cities, land change (plows, tractors, irrigation), selective breeding, genetic engineering, transportation, resource extraction.
  • Diminished Natural Selection: Normal natural selection is less influential.
    • E.g., development of medicine, use of eyeglasses.
  • Energy Use: Requires energy use.
    • Fire first.
    • Fossil fuels, renewable energy, nuclear.

Language - Foundations

  • Needed Evolutionary Foundations:
    • Vocal control (morphology).
    • Social complexity, selective advantage for better communication.
    • Advanced theory of mind (understanding of other minds).
  • Roots of Language:
    • Early primates with intentional signaling and gestures and existing social structures.

Language and Brain Size

  • Paleoneurology Challenges: Difficult to study brain evolution directly.
  • Homo habilis and H. erectus: Possible increase in size of Broca’s Area (speech) and Wernicke’s Area (language comprehension).
  • Visual Aid: Endocasts showing the relative sizes of brains in H. sapiens, Chimpanzee, and A. afarensis.

Language Evolution

  • FOXP2 Gene: Key gene for language, shared between H. sapiens and H. neanderthalensis.
  • Relationship to Society and Technology:
    • As hominids transferred knowledge, norms, and skills socially, language was selected to be more complex (selection feedback loop).
  • Animal Language: Limited number of ideas, fixed contexts, no abstract ideas.
  • Human Language: Can seemingly communicate a near-infinite number of ideas, including new ones or abstract ones.
    • E.g., a bird might warn of a predator's presence but cannot discuss what would happen if the predator were to attack tomorrow.

Symbolism

  • Relationship: Closely related to language and abstract thought.
  • Examples: Burial rituals, cave art, ornaments, and statues.

Conclusion

  • Homo sapiens as a product of cultural and biological evolution.