EVANTH Test 2

WEIRD

Western, Educated, Industrialized, Rich, Democratic

• most people today are WEIRD

Evolutionary Mismatch

Many chronic diseases and other problems common today seemed to be caused by the mismatch between our evolved lifestyle and our modern WEIRD worlds

Hadza

Hunter-gatherers in Tanzania

• dry savannah, acacia trees, dry frame shelter

• communal: ~ 6 kids/woman

Foraging:

• tubers: fibers potato

• baobab: fruit, use tools to process kernels (processing increases kcal/pod, tools are important)

  • women leave camp together to collect plant foods: walk ~8km/day, ~13k steps/day

• honey: men climb and chop trees to collect honey (15% diet)

• hunting: ecologically risky, large game every ~30 days, small game more often, most days nothing. Men hunt alone (quieter).

  • importance of tools: bow and arrows (bows made from ligament, arrow from tree branch, metal traded), poison for arrows, knife, fire

    • tools are sophisticated and they know how to make them

  • men walk ~12km/day, ~19k steps/day to hunt and collect honey

Social structure:

• egalitarian

• polygyny rare

• camp life ~28 people, most distantly or unrelated

Hunter-Gatherer Life

Foraging: hunting, gathering, division of labor

Social: organization, marriage, learning

• Hunting and gathering is a flexible lifestyle. Lots of diversity across time and space.

• Homo is the hunter-gatherer genus

Foraging (Hunter-Gatherer Life)

Finding and acquiring food.

• hunting is ecologically risky → it only works because humans share

• most hunter-gatherers have a gendered division of labor: men hunt animals, women gather plant foods

  • based on cultural or evolutionary things (hunting ecologically risky)

• Tools important for hunting and processing food.

Social Structure (Hunter-Gatherer Life)

Egalitarian. No “chief,” government, hierarchy. Women = men.

• No rule allowing people to tell each other what to do

• connections based on tribe (language group, culture) > camp/”band” > extended family > family > marriage

Marriage: universal → mix of courtship and arranged

• men: ~23, women: ~19

• polygyny usually permitted (1 guy, multiple wives)

Camp life: ~28 people living together, most are unrelated or distantly related

• alloparenting: child care from non-parents

  • kids learn how to forage from parents and others

    • foraging requires complex, learned skills (don’t reach adult proficiency until ~20)

Ceramics/pottery

Multiple independent origins.

• Earliest ~20,000 years ago in China

Neolithic Revolution

Farming (plants and animals) begins ~12,000 years ago

• Western Asia first → multiple independent events

  • multiple origins: Fertile Crescent, Yangzi and Yellow River Basins, Central Mexico, Northern South America, Eastern USA then geographic expansion

    • goats, sheep, cows (Africa and Eurasia)

    • cereals (near east)

    • chickens (Southeast Asia)

    • corn, potatoes, tomatoes (Americas)

Agriculture

Multiple independent origins, earliest ~12,000 years ago. Langauges spread as farming cultures spread. So much calories, so much spread.

• 12,000 years ago: Fertile Crescent, Near East (wheat, barley)

• 8,500 years ago: Yangtze River Valley (rice)

• 8,000 years ago: Yellow River Valley (millet)

• 7,500 years ago: New Guinea Highlands (taro, banana)

• 7,000 years ago: Mesoamerica (maize, beans, squash)

• 7,000 years ago: Andes (potatoes, quinoa)

• 4,500 years ago: Eastern North America (sunflower, marsh elder)

• 4,000 years ago: Sub-Saharan Africa (sorghum, millet)

Animal Domestication

Multiple independent origins

• 11,000 years ago: Anatolia (sheep, goat)

• 10,000 years ago: Euphrates (cattle)

• 6,000 years ago: Andes (llama, alpaca)

• 5,000 years ago: Central Asia (horse)

• 3,400 years ago: Southeast Asia (chicken)

• 2,000 years ago: Mesoamerica (turkey)

Metallurgy

Four independent origins

• 7,000 years ago: Balkans

• 7,000 years ago: Anatolia

• 3,500 years ago: Niger

• 2,700 years ago: Andes

Wheels

2 or 3 independent origins

• 5,500 years ago: ~3 disputed origins around Eastern Europe and Middle East

• 3,200 years ago: independent (?) origin in China

• 1,200 years ago: Mesoamerica, only in toys/statues

Writing

All scripts today descend from first 3 origins.

• 5,400-5,200 years ago: Mesopotamia - Cuneiform

• 5,200 years ago: Egypt - Heiroglyphs (from Mesopotamia?)

• 3,200 years ago: China - Oracle Bones

• 2,500 years ago: Mesoamerica - Olmec

• Andes: Khipu (4,500 years ago)

• Australia: talking sticks (unknown age)

Architecture

Monumental public works → enormous cooperative/collective projects

• 11,600 years ago: Gobekli Tepe

• 6,500 years ago: Carnac, France

• 5,300 years ago: Liangzhu, China

• 5,500 years ago: Watson Brake, Louisiana

• 5,000 years ago: Stonehenge

• 4,600 years ago: Pyramids, Egypt

• 4,600 years ago: Caral, Peru

Population Growth

Stems from agriculture → growth of empire and large cities. World population jumped to billions.

• Rome: first city to 1 million

Industrialization

Industrial Revolution in the 1700’s

Modern, industrialized life vs past

• We live with many more people: urban environments, kin are dispersed

  • Median living area population size: 28 hunter-gatherers, 17,500 US

  • Most people live in cities and towns

  • less social

• Life is spent indoors: artificial environment, artificial light

• Food is highly processed: energy dense, hyper palatable, abundant

  • most calories in US from added sugars (syrup), added fats

• Much less physical activity: more time spent sedentary

• Fewer microbes (bacteria, viruses, parasites): antibiotics, vaccines, plumbing

  • increased life expectancy, lower mortality (particularly childhood)

Evolutionary Mismatch and Health

• Natural Environments decrease stress

  • Shinmin-yoku

  • experiments with stressful video then videos of city or nature → nature more calming

  • stress → epinephrin (immediate leads to higher heart rate, higher blood pressure) and cortisol (long-lasting, negative feed loop)

    • chronic stress → chronically high cortisol, HR, BP, etc.

• living life indoors increases risk of myopia

  • Bad eyesight rare for Hadza

  • Poor sight from low light, close up (near work activities)

• artificial light affects sleep and circadian alignment

  • foragers and farmers: 6-7 hours sleep/night → seasonal: more in winter

    • start sleeping ~3 hours after sunset

    • very regular and aligned with sunlight

  • Industrialized, modern environments: 6-7 hours, much more variability, often not aligned with sunlight

    • sleep duration and irregularity → increased risk of illness

Shinrin-yoku (forest bathing)

Taking int he forest atmosphere → lower cortisol.

Myopia

near-sightedness

Chronotype

When do you naturally go to sleep and wake up?

Social Jet Lag

When do you wake up vs when do you want to wake up?

Urban vs Nature Environments

• Natural Environments decrease stress

  • Shinmin-yoku

  • experiments with stressful video then videos of city or nature → nature more calming

  • stress → epinephrin (immediate leads to higher heart rate, higher blood pressure) and cortisol (long-lasting, negative feed loop)

    • chronic stress → chronically high cortisol, HR, BP, etc.

Time spent indoors and eyesight (Myopia)

• living life indoors increases risk of myopia

  • Bad eyesight rare for Hadza

  • Poor sight from low light, close up (near work activities)

Sleep and Circadian Health

• artificial light affects sleep and circadian alignment

  • foragers and farmers: 6-7 hours sleep/night → seasonal: more in winter

    • start sleeping ~3 hours after sunset

    • very regular and aligned with sunlight

  • Industrialized, modern environments: 6-7 hours, much more variability, often not aligned with sunlight

    • sleep duration and irregularity → increased risk of illness

Biology of Behavior

Stimulus (sight, sound, activity, etc. taken in) → Neurotransmitter → hormones → behavior

Hormones

Made in gland and tissues travel via blood to carry signals throughout the body. Chemical signals between organs.

• hormone must be made and have a receptor to work

• Leptin, GHRELIN, GLP1: hunger and fullness, affects eating behavior

  • GLP1 → increased insulin, decreased glucagon, slows digestive system (gastric emptying) → lower appetite

  • GLP1 drugs are effective and change behavior (weight loss drugs mimic GLP1)

• Estrogen: affects normal socio-emotional behavior

• Testosterone: competition, libido, aggression, courtship

  • winner effect: increased testosterone pre-game, winner’s cortisol increases post-game, loser’s testosterone decreases

• Cortisol: stress. Affects a range of behaviors: mating, eating, reproduction.

Neruotransmitters

molecules made in the brain, signal from neuron to neuron. Chemical signals between neurons in the brain.

• Dopamine, serotonin, and others released in response to food, sex,…

  • ancient → even worms release when finding when finding food

  • SSR1 anti-depression drug: increase the effect of sermonic in the branch

• Oxytocin: “cuddle chemical” affect maternal behavior and bonding

Genes

Belyaev Fox Experiment (1950;s Russia): start with population of wild foxes

• phenotype: aggressive (don’t breed), cautious/friendly (breed)

  • individuals. differ in these pathways leading to different responses. Genes shape these pathways.

Vasopressin:high receptor density in Prairie Vole (monogamous), law in meadow vole (polygamous)

• receptor density increased in meadow vole → became monogamous

Biohacking behavior in evolution

• Zombie ants: ophiocordyceps fungus infects ants, releases chemicals to take over brain.

  • causes ants to leave nest, climb upward, bite the stem

  • different cordyceps for different species

• Toxoplasmosis and mouse behavior: parasite reproduces in cat gut

  • mice infected lose their natural fear of cat odor

  • tentatively linked to mental illness in humans

learning and conditioned response

Pairing stimulus and consequence.

Conditioned response

• First unconditional stimulus that leads to reward/avoidance without training

• pair unconditional stimulus with neutral stimulus

• Neuron stimuli → same response as unconditional stimulus

  • Pavlov: neutral bell, unconditional food

Unconditioned stimuli: don’t require learning

• flavors, pain, social/emotional connection: shaped by evolution, brain structure

• rats associate nausea with food, not light or sound, associate pain with light and sound, not food

Associations can be maladaptive or harmful: addiction, PTSD

Humans learn differently than other apes

• both: understand space, socially interact (help)

• chimps can’t understand humans trying to help/teach

• ape: right vs wrong way doesn’t matter → do their own way.

• children: copy even if unnecessary.

• All apes (including us) learn complex tasks

• humans are unique: actively teach each other, actively learn and imitate

How did human psychology and behavior evolve

Costs and benefits of living in groups

(Nearly) all primates live in groups (social). Evolutionary interpretation: benefits of group living > costs of group living.

Costs (solitary)

• competition for resources

• risk of contagious disease

• interference with reproduction

Benefits (social)

• protection from predators

• resource defense

• cooperative foraging

• help with infant care

Social organisation in primate evolution

Common organization: Main group (few males, many females and kids) and bachelor group (adult males with no females)

• female sociality balances access to food and predator protection (resources and risk predation)

• male sociality maximizes access to females (mating)

Gibbons: Monogamous (pairs), territorial, sing to defend borders

Orangutans: solitary, male dominant

• Gibbons and orangutans have a boom and bust cycle of fruit → smaller groups

Gorillas: polygynous (one male, multi-female), male dominant + bachelor groups

Chimpanzees (Pan troglodytes): multi-male, multi-female, fission-fusion communities (females grow up and leave, males stay), male dominant → fight

Bonobos (Pan paniscus): multi-male, multi-female, fission-fusion communities, female dominant (coalition keeps males in check, male standing based on closest female friend) → sex (+ same sex too)

Humans: pair bonds within multi-male, multi-female. Sharing, egalitarian, social, cooperative

Social Behavior

When to play nice

Kin selection

Natural selection acts on traits that affect inclusive fitness.

• Hamilton’s rule: helping is favored by natural selection if r B > C

  • r: recipient’s relatedness to helper

  • B: fitness benefit to recipient (recipient’s offspring)

  • C: fitness cost to helper (helper’s offspring)

• example) helping raise 3 nieces/nephews costs you an offspring: fitness cost 0.5 < fitness benefit 0.75

  • Kin selection logic: helping sibling raise 3 nieces/nephews is favored. Inclusive fitness is 2.25 ( 3 kids with 0.5 of genes + 3 nieces/nephews with 0.25 of genes) > 2 (original)

• Eusocial species: only queen reproduces

• Helpers at the nest: offspring help at next even after maturity

• Grandmothering in humans: increased newborn survival rate with grandmother present

Inclusive Fitness

The genes you pass on plus the genes you pass on through your relatives (because they share some of your genes)

Altruism

You get a negative and others get a positive effect. Hard to explain.

• kin, group selection?

  • Humans share and help in many cases where recipient is not kin

• all apes are social and can work together → humans much more social and cooperative (share fairly)

• altruism good for group (self-domestication)

Cooperation

You and others get a positive effect.

• Favored in group selection (rare, controversial, requires very specific conditions to evolve): favors cooperative individuals within selfish groups

Selfishness

You get a positive effect and others get a negative effect.

• Easy to explain → common and expected in individual selection.

Spite

Punishing rule-breakers. Bad for you and others.

• Group selection vulnerable to free-riders and cheaters → need to punish cheaters and enforce social norms

Self Domestication Hypothesis: in-group vs out-group

Humans evolved to be tolerant and nice to in-group members. Individuals who were intolerant/not nice were excluded → low fitness (friendly foxes study)

• By Brian Hare at Duke.

• could explain why humans show changes in skull shape that are similar to domesticated species → implies H. sapiens self domesticated but other hominins did not.

Nature and Nurture

Ultimatum game shows nurture (people offering more of a percent of what they have (closer to 50%)

Evolutionary Mismatch: Egalitarian

Hunter Gatherer: very little inequality in wealth and power

WEIRD: development associated with high wealth inequality (gini coefficient → 1 most unequal)

• social inequality may be associated with poor mental health (depression)

Evolutionary Mismatch: Social

Hunter Gatherer: close, daily connection to friends and kin

WEIRD: loneliness and social isolation are increasing

• loneliness and social isolation associated with increased mortality and poor mental health (anxiety, depression, etc.)

Evolutionary Mismatch: Risky

Hunter Gatherer: real, daily risks and dangers

WEIRD: don’t encounter the same risks.

• risky play is associated with better mental health (less anxiety)

Trophic Pyramid

The energy in food ultimately comes from the sun.

• Sun > plants > herbivores > carnivores

• each step only retains ~10% of the calories

Evolution of the Human Diet

Primates (including humans) eat a variety of foods (different properties).

• primate (non-human) diets: lots of fruits, leaves, some have insects or seeds

Humans:

• eat stuff that other primates don’t eat (tubers, lots of meat, etc.)

• really high-quality diet compared to their body size

  • stomach acid is very acidic (similar to scavengers) → evolved to scavenge meat

• meat in diet (tools and butchery)

• plants in diet (shape of teeth and microfossils of plants stuck in the calculus)

Hunter-gatherer diets are diverse: geographic variation → cold, fishing, pastoralism: more animal foods. farming: more plant foods

• no singular natural human diet

• no evidence that past hunter-gatherer diets were exclusively low carb or carnivore

Basic food properties: energy vs abundance

Energy density: Higher calorie-dense foods are harder to come by

• Leaves (cabbage, lettuce, etc.) < roots (carrots, potatoes, etc.) < fruits < meat

• High quality foods are high in energy but low quality foods are more abundant

Different food properties:

• leaves: low in energy, very abundant in nature

• seeds: often difficult to digest, protected by chemicals ad shells

• fruit: high in energy, easy to digest, less abundant than leaves

• root vegetables (tubers): high in energy, difficult to find and harvest

• meat (including insects): highest in energy and protein, difficult to get.

Fire and cooking: energy availability increases with cooking

• potatoes: energy/g doubles with cooking

• humans require cooked food

• earliest fire ~1mya wonderwerk cave

Angiosperm coevolution Hypothesis

Plants that provide fruits coevolved with primates. Plants provided energy, primates provided seed dispersal.

• fruits give energy, primates eat fruit, primates poop the seeds out elsewhere, new plants grow, cycle continues

• Primate diets: fruit and leaves most common, small-bodied species

Kleiber’s Law (food quality vs body size)

Bigger organisms burn more calories per day

• an animal that is 10x bigger burns ~7.5x more calories

  • pound for pound, smaller animals burn energy faster

  • smaller animals need high-quality food because they eat less and burn energy faster

    • insects, fruit, sap, etc.

  • larger animals don’t need very high quality food because they eat more and burn less energy

    • leaves

Allometry

the relationship between a trait of interest and an organism’s body size. Used to investigate patterns of variation.

Adaptations to different diets

Teeth:

• Frugivores (fruit-eaters) have big incisors and rounded molars (like humans)

• folivore (mostly eats leaves) small incisors, molars with shearing crests

• insectivory high, sharp cusps on molars, strong incisors

Brain:

• Color vision, emphasis on visual/tactile cues for fruit ripeness

• tools and big smart brains

• high-quality foods are hard to acquire → creates selection for intelligence to find food

Intestine length related to body size and diet quality:

• human consistent with high diet quality (less total intestines)

Optimal Foraging Theory

Organims try to maximize energy gain, minimize effort.

Food quality vs territoriality

Fruit specialists: more territorial'.

Leaf specialist; less territorial

Monkeys and apes: >90% plants

Evidence for hunting

2.5 mya with Early Homo

• oldowan tools, butchered bones, meat in the diet

Expensive Tissue Hypothesis

Hunting and gathering: energy rich, easier to digest diet that is challenging to acquire (need to be smart). Gut size decreases, brain size increases.

• brain uses lots of energy, can only get more energy when gut decreases if food is more energy rich

Modern Human Diets

Mixed trophic level strategy (50,50 meat, plant)

Herbivore

• gathering: low risk, lower reward

carnivore

• hunting: high risk, high reward

• hunting ecologically risky → only works because humans share

• spoiled and rotting meat common

sharing: maximizes dependable energy availability

Honey: an important part of the diet for warm-climate hunter-gatherers

• chimps and other hominoids eat honey. Early hominins likely did also

  • greater honeyguide indicator

carbohydrates: blood sugar and glycogen

fat: fat → glycogen

protein: muscle and other tissue

Domestic plants: more energy, less fiber, fewer nutrients

Domestic animals: twice the fat

modern diet dependent on grasses (farming and processing)

Diet and evolutionary mismatch

obesity and obesity related mortality are increasing globally

• ultra-processed foods drive us to over consume and gain weight

  • dominating our diet

• increased ultra-processed foods in diet → increase body fat %

• optimal foraging in humans: higher energy dense foods cheaper

  • modern diets are more energy dense → may contribute to obesity

• diets work if you stick to them

Ape activity levels

Daily life for non-human apes is pretty low energy

• ½ day resting and grooming

Homo: hunting and gathering change in energy usage

• persistence hunt

• hunter gatherers get 3x more physical activity than other apes (for industrialized much lower)

Endurance Running Hypothesis

Homo erectus (and maybe earlier Homo) was adapted to run long distances to hunt and scavenge prey.

• long legs, foot arch, narrow pelvis, large leg joints, 6’ tall, 60 kgs

Persistence hunting:

• breathing separate from running, no fur (don’t overheat)

Sources of mortality in the past and today

1900’s non-infectious diseases became the leading causes of death

• before 1900s mostly infection

cardiovascular disease on the rise

• 1950 London bus study: conductors (stand and walk all day) much lower rate of heart disease than drivers (sit)

Low levels of physical activity associated with poor health → physical activity reduces cardiovascular disease risk and mortality

Effect of physical activity

Health benefits of exercise extend throughout the body

mortality rates: decrease with physical activity

blood pressure: improves blood pressure

• blood vessel health: shear stress on vessels from increased blood flow increases NO and vessel elasticity

inflammation: increases during exercise but regular exercise reduces chronic inflammation levels

reproductive hormones: regular physical activity reduces levels of estrogen and testosterone. may explain reduction in reproductive cancers with exercise

stress and mood: regular physical activity reduces levels stress hormones (cortisol and epinephrine) and improves mood

cognition: aerobic exercise promotes brain growth and perfusion and protects against age-related cognitive decline

Sedentary behavior: heath risk even for people who exercise regularly

Daily physical activity and energy expenditure

No difference in daily expenditure. Lifestyle does not equal calories burned. Energy of captive primates = energy of wild primates.

Constrained energy expenditure hypothesis

As you exercise you take away energy usage for other non-necessary functions and use it toward physical activity so daily energy expenditure stays the same.

• human exercise intervention studies

• metabolic compensation may be an important reason exercise is so good for us

• less inflammation, stress reactivity, reproductive hormones

Life Expectancy

life expectancy very low for hunter-gatherers. High childhood mortality.

• Most death in these communities are caused by infections

  • affects youth and older the most

  • number one killer throughout human evolution

• quite a bit from homicide and warfare and accidental

• US arguably safest

Farming and larger settlements likely increased infectious disease burden

• transition to farming associated with smaller stature (energy going towards fighting disease) likely due to disease

• increased fertility and mortality rates

Immune System

External

• skin: physical defense. secretions contain lysozymes (enzymes that destroy bacterial cell walls)

• Mucous: lungs and mucous membranes. Contains lysosymes

• Cilia: in the respiratory tract, move mucus out of the lungs to keep bacteria and viruses out

• Stomach acid: kills pathogens in food

• Genitourinary tract: acidity of urine, vaginal lactic acid

Internal

• Bone Marrow: immune cell propuction

• Thymus: T cell maturation

• Lymph nodes and vessels, spleen, adenoids, tonsils: surveillance and destruction of pathogens (bacteria etc.)

• Molecules:

  • Interferons inhibits viral replication

  • complement destroy bacteria, stimulate immune response

  • pyrogens produce fever

  • Leukocytes: army of immune system cells produced in bone marrow

Innate

• recognize foreign or damaged cells or other pathogens and isolate/destroy them

  • rapid response

  • can be fooled: incorrect identification of foreign or pathogen leading to allergy, asthma, autoimmune disease

Adaptive

• identify specific pathogens (learned)

• produce antibodies to mark those pathogens for destruction

• some T cells kill recognized invaders

Antibodies

Antibodies (immunoglobulins): 100 million trillion in each person, representing millions of specificities to different antigens

• attach to pathogens to mark them for destruction

• stimulate complement production to destroy bacteria

Germ Theory of Disease

Illness is a response to antigens (any foreign substance that elicits an immune response)

Bacteria: cells with cell membrane can reproduce on their own

• killed by antibiotics

Virus: DNA or RNA wrapped in a capsid protein coat

• must use host machinery to reproduce

• no effect of antibiotics

Parasites: multicellular or single-cell organisms that require host for survival

Prions: misfiled proteins

• no cure

Vaccines

Illicit an antibody response (adaptive immunity) through intentional exposure to similar but less harmful pathogen

• inoculation (variolation): introducing related or weakened pathogen from other infected individual

• Vaccination with inactivated virus: dead or “inactivated” virus injected into recipient

• mRNA Vaccines: inject mRNA, cells make portions of the virus

Vaccine Hesitancy: as old as the practice itself

• 1720s: Boston inoculation campaign (smallpox) → firebomb

• 1990s: vaccine-autism scare → debunked

• 2020s: covid vaccine hesitancies → risks for children and other vulnerable groups

• Measles made a comeback because vax hesitancy

Antibiotics

Microbiome

Hygiene Hypothesis vs Old friends hypothesis

GLP1 and GIP drugs