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.
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.