Lecture Notes on Human Evolution PDF

EXAM 2 October 1, 2024 What is a Hominin? Hominoid (Apes) Us, our ancestors, great apes, lesser apes (gibbons, siamangs) Hominid (Great Apes) Us, our ancestors, great apes (chim...

EXAM 2 October 1, 2024 What is a Hominin? Hominoid (Apes) Us, our ancestors, great apes, lesser apes (gibbons, siamangs) Hominid (Great Apes) Us, our ancestors, great apes (chimps, gorillas, orange) a broader group of primates Hominin Us, our direct ancestors more narrowly focused on humans and species closely related to us after the split from the chimp lineage Human-Chimp Last Common Ancestor: (hominin with very close traits to chimps) Lived ~6million years ago Closer to chimp-sized brain and body Long arms and fingers and grasping foot - foraged (swinging) in tree Large canines - sexually dimorphic meaning difference in app rea ce bet ween males and females beyond the difference in reproductive organs (Ex: size; males were likely to be larger then females) Quadrupedal Ate almost entirely plant food Showed many chimp All species that evolved like characteristics after the split bet ween the lineage that would evolve into Homosapiens and the lineage that would evolve into chimps show bipedal characteristic that shows distinguishes hominins from chimps Australopithecus afarensis: Hagar, Ethiopia - A.L 288-1 - “Lucy” date: ~3-4 mya Brain size = modern chimp What was unique about Australopithecus afarensis was that… Short, broad pelvis (derived) which was useful for walking on t wo legs Femur angled toward knee (derived) which was a sign of bipedalism Big toe in line (derived) which provides stability for walking on t wo legs Arms relatively longer than humans Curved fingers which suggests that she probably spent some time swinging in the tree Why did hominins evolve bipedalism? The evolution of bipedalism is very likely tied to changes in the subsistance strategy of hominins and the evolution of hunting and gathering like subsistence strategy Homo habilis - ~ 2.4 mya Reduced facial size Moderate-small browridges Encephalization (a change in brain size; increase in brain size relative to body size) Homo habilis - 630 cc (expansion of the brain compared to other from before) - Paranathropus - 520 cc - Australopithecines - 442 cc Possibly the first hominids to use stone tools (ex: rocks to ground food into a form easier to digest) **But maybe not** (new fossils are found and show that maybe not) - hunter-gatherer subsistence strategy Homo erectus - ~ 2 mya, E. Africa 1st hominid group found outside of Africa Oldowan-style tools (type of stone tools) Body Size - weight > 100 lbs; average height ~ 5’6” - “Nariokotome Boy” - Kenya Brain Size - cranial capacity bet ween 750 - 1250 cc - overlaps modern human cranial capacity Possibly existed as a species for over 1 million years Left off at min 23:45 What are “Premodern Humans”? Stereotypical view of Neandertal What does it mean to be human? Premodern humans - “archaic H. Sapiens” - no clear consensus but usually includes H. Neanderthals sis, Denisovians and H. heidelbergensis DIstinguishing features - thick skull, prominent brow ridges, lack of chin  Anatomically Modern Humans Evolved in Africa 300-300 kya Human Settlements with plant and animal domestication arose 4,000 - 12,000 years ago in multiple locations Evolutionary Mismatch Hypothesis: WEIRD Bodies: Western Education Industrialized Rich Democratic (WEIRD) “Medical science’s understanding of human health and disease relies heavily on people of Europea descent living in a contemporary urban, industrialized environment” Disability-adjusted life years (DALYs) - reflect the total number of years lost due to illness disability and premature death - combines the effects of morbidity and mortality the way populations in WEIRD countries use their bodies is different from humans in our evolutionary past The way population in WEIRD countries use their bodies is different from contemporary populations in non-WEIRD countries We need to understand the full spectrum of human biological variation and its origins if we’re going to improve human health Caveats - many environmental changes that are common in WEIRD countries benefit our health - ancestral environments don’t always promote health  Critiques - focus on WEIRD vs non-WEIRD regions hides the dramatic variation within populations - variation in life expectancy at birth across neighborhoods in US spans the range across countries globally - important variation across non-WEIRD regions - history of anthropologist conflating the lifestyles and environments of non- WEIRD regions with the lifestyle and environments of our evolutionary past - “Demographic difference and force of selection” section - article falls into adaptationist trap “Preventing and treating disease requires both expanding study design to sample diverse populations and context and fully incorporate evolutionary perspectives” “Local and recent adaptations to specific environments require us to think critically about how to apply one-size-fit-al remedies to improving health”  October 8 Anatomically Modern Humans Evolved in Africa 300-200 kya somewhere bet ween 40 and 60 thousand years ago we started to spread out because Homo sapiens evolved in Africa and stick around for over 100,000 years, most human genetic diversity evolved in Africa genetic diversity outside of Africa is a subset of what exists within the content due to founder effect and genetic drift (As humans began to spread through the continent humans were taking the genes with them that they had evolved in Africa; majority of Allie’s can be found in Africa *min 5:45*) 3 Main Critiques of Races as Genetically Determined Category: 1. Human genetic variation is clinical Clines and Substructure - Cline - frequency of variants (Allen’s or phenotypes) is high in some geographic regions and gradually become less frequent as one moves away from the region the sickle cell aleles are found in parts of the world that have flooding agriculture meaning its not just seen in Africa but its was seen very common in Africa. within clines there is population substructure - clustering of alleles frequencies within a cline Due to non random mating and periodic isolation Genetic is choose the number *min 11* K refers to the # of clusters *overall message at min 13:18*  2. Most human genetic variation is discordant meaning, the traits we use to distinguish race are independently inherited and have no value for predicting other aspects of biology - for example, having a specific color skin doesn’t mea they predict other genes that are inherited separately like hair texture 3. Human genetic variation is widely shared across the species, with little variation occurring bet ween racially definiéndoles groups (99.9% of human genetic variation is shared) How has natural selection shaped the human genome? Selective sweep - when a beneficial novel mutation increases in frequency in a population through natural selection What shapes the variation of that 1% of human genome variation? Genetic drift and mutation *min 17:15* Hard selective sweep model - Humans migrate into new environments -> strong selection for novel beneficial mutations Polygentic adaptation - Natural selection for multiple alleles that already existed in the population - Each allele has a small effect on the adaptive phenotype - A faster mode of adaptation because it is relying on genetic variation that already exists *min 20*  - There are more examples of poly genetic adaptation Examples of selective sweeps in the human genome - skin pigmentation because *min 21-23* our body uses UV radiation to produce vitamin D; in colder environments (less UV radiation) there is natural selection for light skin and vice-versa for dark skin - metabolic adaptation to cold climates (Alaskan-native populations have a higher frequency of alleles that lead to a higher *min 24* - lactose tolerance - infectious disease susceptibility - Malaria and the sickle cell allele - adaptation to high altitude hypoxia “Racial experience in the age of direct-to-consumer ancestry testing” “DNA ancestry tests don’t actually tell us where our ancestros lived. They’re really just giving us probabilities of where we’re likely to have relatives today.” How do genetic ancestry tests work? - compares test-taker’s halogroups to the frequency of halogroups in reference populations - Halogroup - a group of similar halo types that share a common ancestor What halogroups do you have? - Which reference populations have a high frequency of your halo types? What is a reference population? - Any population that serves as a comparison for a genetic ancestry analysis - the genetic clustering in a reference population depends on which individuals are included in the data base - Group(s) of individuals that are being used as a comparison Changes in the reference group data can change the results of the test How are reference populations defined? - Names of reference groups are shaped by history, culture, politics, and other social identities  Halotype: Video(s) watched in class: https://youtu.be/rZJCOhCfq3E?si=5ToTWilm080dBlyF https://www.youtube.com/watch?v=Ur7Fu2-jYAY&t=92s Dr. Jada Benn Torres argues that genetic ancestry testing can … Refit biological notions of race Empower communities by shaping racial experience What about the “racial medicine”? Video: https://www.youtube.com/watch?v=KxLMjn4WPBY Dr. Dorothy Roberts Nutritional Transitions and the Paleo Diet October 17 Dietary Adequacy extent to which food intake fulfills one’s nutritional requirements Typically assessed using a 24 hour dietary recall Six broad categories of nutrients need to sustain life Macronutrients - carbohydrates - protein - fats Micronutrients - vitamins - minerals - water -> Carbohydrates accounts for ~40-50% of daily calories among U.S adults (Breifel & Johnson, 2004) Simple carbohydrates - Monosaccharides -Glucose, fructose, galactose - Disaccharides - Sucrose Complex Carbohydrates - Polysaccharides - Starch - Nonstarch polysaccharide Ex: Dietary fiber -> Protein composed of amino acids - body requires 20 different amino acids - essential amino acids - 9 amino acids that cannot be synthesized by the body - Arginine, cysteine, glutamine, glycine, proline and tyrosine -> Fats simple - triglycerides - composed of glycerol and fatty acid - saturated and unsaturated fatty acids compound - phospholipids and lipoproteins derived -> Vitamins not a source of energy, helps the body use energy and carry out other metabolic activities Folate - type of vitamine B - found in green leafy vegetables, citrus fruit, dried legumes - need for fetal development, spermatogenesis, the production of neurotransmitters like serotonin vitamin D - found in oily fish, liver, some plants and mushrooms, fortified dairy products - need for skeletal growth and maintenance and immune function -> Minerals inorganic elements that are Kent components in many biological molecules Calcium - needed for skeletal growth and development - found in dairy products, leafy greens, beans and nuts Iron - needed for hemoglobin (protein that carries oxygen in the blood) - found in meat, beans, and dark green leafy vegetables The History of Agriculture: https://youtu.be/Yocja N5s11?si=itSRc1BL×BYWEKX5 The Consequences of Agriculture for Human Health: shift towards carbohydrate-based diet Skeletal signs of nutritional deficiencies in archaeological record - Dental caries - Pathological conditions of the Skelton - Lower cortical bone thickness - Reduction in skeletal growth - Greater infant and childhood mortality - Lower mean age-at-death Dramatic increase in population size Increase in infectious diseases Greater inequality Variation in its affects due to differences in geography, politics, culture, and population size What is the Paleolithic? period that begins with hominins beginning to use stone tools ~3.3 million years ago Ends with the last glacial period (c 11,650BP) “Is there an Optimal Diet for Humans? The Tsimane in The Hadza in Tanzania The Shuar in Ecuador  “Paleo Diet” argues that a healthy diet should mimic the diet of Paleolithic hunter- gatherers - Human digestion and nutritional needs are not adapted to diets that are common post agricultural revolution specific macronutrients composition - 35% of calories should come from protein - 45% of calories should come from carbohydrates - mostly non-starchy fruits and vegetables with high fiber - 28-47% of calories should come from fat - Low saturated fat foods avoid added sugar,dairy, grains, starchy tubers, and legumes Support for the “Paleo Diet” archaeological evidence indicates that agriculture does not inherently lead to healthier populations Diets rich in added sugar, low fiber, refined carbohydrates are associated with metabolic disease Insufficient time for substantive genomic adaptations to contemporary diets Exceptions - lactase persistence - enhanced salivary amarla se production in populations with starchy diets Health of Hunter-Gathers: Hunter-gatherer population shave low rates of chronic sI eases such as - heart disease, hypertension, diabetes cancer expected Lifespan at Birth: 30-40 years old - due to high infant mortality from infectious disease expected Lifespan at Age 15: 72 years old Critiques of the “Paleo Diet” There is no single Paleolithic diet - Wide variation in macronutrients composition and plant- v.s animal-derived foods across populations - Wide variation across seasons and years Archaeological evidence for consumption of some cereals, starchy tubers and legumes during Paleolithic Not all aspects of modern diets are intrinsically unhealthy Variation in Human Diets: Common Characteristics of Hunter-Gatherer Diets: composed of a mix of meat, fish and plants More fiber in hunter-gatherer diet than typical American diet Most of the carbohydrates come from vegetables and starchy plants - Low glycemic index -> measure of the effects of a food on blood glucose levels Nutrition Transition: Shift: substance -> wage/market economy Increase availability of market foods and energy Reduced activity and energy expenditure Physical Activity and the Constrained Total Energy Expenditure Hypothesis: Conditions of Evolutionary Mismatch: “Mismatch conditions are defined as diseases that are more prevalent or more severe today than in the past because the body is inadequately or insufficiently adapted to modern environments” (Lieberman 2015) Sedentary Lifestyles as an Evolutionary Mismatch: What do we know about physical activity across our evolutionary ancestors? last common ancestor (LCA) bet ween humans and chimps has many chimp-like characteristics Chimp physical activity - t wice as strong as humans - walk less than 1.5 miles/day - Rarely sprint - Leg muscles are mostly fast-t witch fibers - Can’t cool effectively through sweating Fast-Twitch vs Slow-Twitch Muscle Fibers: Fast Twitch: Slow Twitch: can split ATP very quickly More metabolically efficient Rely on anaerobic metabolism Rely on aerobic metabolism Can contract 2-3 times the rate as Slower speed of contraction slow t witch Greater endurance than Good at generating short bursts of fast t witch strength or speed  evolution of bipedalism in Autralopethiecus pronounced adaptations to bipedalism in Homo erectus - Persistence hunting Evidence to support that Homo erectos was using persistence hunting - expanded gluteus Maximus - short toes - head stabilization for running Humans evolved to be adapted for regular, modest amount of endurance physical activity - more slow-t witch muscle fibers - evolved efficient sweating for thermoregulation - large glutes  Humans also evolved to avoid unnecessary energy expenditure Evidence to support this interpretation - Humans have a higher percent body fat than other primates - chimpanzee - 5-8% - Hunter-gatherer males- 10-15% - Hunter-gatherer females - 15-25% - Adaptation to intermittent caloric scarcity - Data from contemporary hunter-gatherers - Often stay close to energy balance - Periodic scarcity and abundance depending on the season - Muscles consume `40% of RMR - Muscles hypertrophic or degenerate depending on use - Many other systems (i.e circulatory, skeletal, nervous system) are activated during PA or degenerate under sedentary conditions Health Benefits of Exercise: reduces inflammation Improvements to heart muscle and circulatory system Prevents dysregulation of metabolic system Prevents bone loss Improvements to nervous system Does exercise help with weight loss? https://youtu.be/PnKrQXt44nQ?si=v5RPikw8cAQhWHZx Human Energy Allocation Model: The allocation rule: in most organisms, the energy budget is finite, and thus must be allocated across competing biological functions The Constrained TEE Hypothesis: Additive Model of TEE TEE = BMR + PA + thermogenesis + immune function + digestion + reproduction, etc  TEE is constrained at high levels of physical activity Exceptions to the Constrained TEE Model? Adaptive thermogenesis - when metabolic rate is lower than expected after a persona consumes a meal - pattern detected in some individuals in response to dieting (i.e negative energy balance What types of exercise should we do? How much exercise? An evolutionary perspective predicts… - a sedentary lifestyle -> poor health outcomes - there are costs and benefits ti each form of exercise - benefits of a mixture of activities - dependent on age and fitness needs - to increase PA, exercise should be fun or unavoidable The Evolutionary Arms Race and Epidemiological Transitions: October 25 Evolutionary Arms Race: https://www.youtube.com/watch?v=tx9ZY04991Q Host species and parasitic species evolve escalating adaptions and counter-adaptions Resembles geopolitical arms race Example: COVID 19 virus - virus infects host - Infected host develops antibodies - Virus mutates into new strain that can bypass antibodies - Infected host develops new antibodies - Virus mutates again… Morbidity vs Mortality: Morbidity = the rate of a disease in a population Mortality = the proportion of deaths in a population Epidemiological Transition: A model for integrating epidemiological and demographic changes in human populations Based on the observation that… - Nations that experience a decline in infectious disease mortality exhibit - an increase in life expectancy - an increase in chronic disease morbidity  Critiques of the concept - Use of the whole nations as a unit of analysis - obscures variation within nations - Dual burden in middle-income countries - increasing rates of chronic disease - persistence of high infectious disease mortality Barre t et al. (1998) Article argues that there have been three main epidemiological transitions throughout human history First Transition: Lower infectious disease burden during the Paleolithic - Early hominids groups were too small and too dispersed to pass on many pathogens Long-standing hominid-parasite relationships - Many parasite species that are common among humans and non-human primates Shift from nomadic hunter-gatherer lifestyle to permanent settlements with agriculture ~10,000 years ago -> increase in infectious disease Factors that promoted infectious disease… - Larger population of human hosts - Increased contact bet ween communities - Accumulation of human waste - Domestic animals -> reservoir for zoonoses - Agricultural practices promoted infection - Standing water -> mosquito breeding - Feces as fertilizer -> contamination of food and water - Food storage -> possible contamination - Reliance on staple crops -> micronutrients deficiencies 2 historical trends that initiated the global spread of pathogens - Increasing migration and trade bet ween state-level societies of Eurasia in 5th century - Expansion of these net works into the Americas, Africa and other regions through exploration, conquest, and colonialism Second Transition: Coincided with the Industrial Revolution in mid-19th century in Europe and N.America Decline in infectious disease mortality Contributing factors - Improved nutrition - Pasteurization - Public health care - Home-based primary health care - Vaccinations - Antibiotics Increase morbidity from chronic disease Contributing factors - Air and water pollution - Urbanization - Associated with increase hypertension, depression, anxiety - Mass produced processed foods - Sedentary lifestyles Within industrialized societies, SES, ethics and gender differences are strongly associated with both chronic and infectious disease mortality Third Transition: “An unprecedented number of new diseases have been detected over the last 25 years that are becoming significant contributors to adult mortality.” Contributing factors - Globalization - Ecological disruption - Climate change - Habitat destruction  - Antimicrobial resistance - Factory farming One Health: “Human or livestock or wildlife health can’t be discussed in isolation anymore. There is just one health” - William Karesh Aim - Improve health and wellbeing through prevention/mitigation of crises that originate at the interface of humans, animals and their environments - Emphasis on collaboration Endorsed by: Alaska One Health Group: Formed in early 2013 Meets quarterly to discuss emerging One Health issues Created the Local Environmental Observers Net work - Net work of local observers and topic experts who share knowledge about unusual animal, environment and weather events  October 29 Thermal Comfort and the Energetics of Thermoregulation: Allostatic Response to Cold Stress: 1. Shivering 2. Non-shivering thermogenesis: Heat that is produced through biological mechanisms that are sepearte from muscle t witching shivering Brown Adipose Tissue (BAT): helpful for adapting to the cold because it has a lot of mitochondria and when we feel cold the mitochondria are activated to produce heat BAT increases when Come back to min 11 in 2nd recording Acclimatization to Cold Stress: Increase in BAT Elevated RMR Increase T3 production and tissue uptake Efficient cycling bet ween vasoconstriction and vasodilation (mixed findings) Lower shivering threshold Reduced NST in skeletal muscle Seasonal changes in BMR among indigenous Siberians - Higher BMR -> more heat production Triiodothyronine is the active from of thyroid hormone The rate of T3 production INCREASES in the winter - But the rate at which T3 enters the tissue increases even more, leading to a net decline in blood T3 levels in winter  Developmental Adaptations: My research suggests that early childhood may be a period of sensitivity for plasticity in BAT Genetic Adaptation to Cold Stress: Multiple genes found in circumpolar populations that show evidence of natural selection are known to regulate BAT A majority of alleles identified as potentially adaptive to cold climates are found in low frequencies across the globe Exceptions: - CPT1a and PLA2G2A Allostatic Response to Heat Stress: increase in sweat production Vasodilation Increase in heart rate Increase in blood viscosity Acclimatization to Heat Stress: Increased sweat Increase [sodium] in sweat Elevated core/rectal temperature Reduced cutaneous vasodilation  Developmental and Genetic Adaptations to Heat Stress? -> Produce less sweat because they are sweating across the body -> Maintain cooler body temperature during heat stress Come back to this to finish when listening to lecture Thermal Comfort and Evolutionary Mismatch: Residents in the U.S spend an average of 83 minutes outside during the winter - Only 33 minutes per day in Canada - BAT in NYC Study - average was less than 5 minuets per day during the winter “responses in winter [in Helsinki, Finland] resemble aggravated reactions of non-cold acclimatization subjects.” (Marinen et al. 2004) Project Direct Consequences of Warming Temperatures: Increase in heat-related illnesses - heat exhaustion morbidity - heat stroke - cerebral ischemia Increase in rate of health complications related to cardio metabolic disease (e.g type II diabetes, heart disease, obesity)  Increase in cardiovascular disease morbidity and mortality during extreme cold weather events How should NYC address this problem? CDC recommends gradually increasing the time spend outside over 5 days for outdoor works Biden administration proposals new rules to protect sople that work in the hat - Employers must provide an acclimatization plan What concerns do you have for the health of New Yorkers in a changing climate? What steps have been taken? What changes need to be made? https://www.youtube.com/watch?v=gR-ARIZLoAk