Unit 3_Unit 4 BIO ANTHRO PDF

Unit 3 Class 11 October 21, 2024 1.​ Reconstructing the past 2.​ Evolution of primates 3.​ Evolution of bipedalism 4.​ Earliest hominins Reconstructing the past *Earth has changed over time Ex: continental drift -​ Barriers lead to speciation -​ Continental positions change ocea...

Unit 3 Class 11 October 21, 2024 1.​ Reconstructing the past 2.​ Evolution of primates 3.​ Evolution of bipedalism 4.​ Earliest hominins Reconstructing the past *Earth has changed over time Ex: continental drift -​ Barriers lead to speciation -​ Continental positions change ocean currents, which changes climates Global Climate Change -​ Lots of fluctuation during primate evolution -​ Cooling trend overall in last 65 million years -​ Warmer in every Eocene and early Miocene -​ Cooler and more variable in Pleistocene -​ Primates evolve in the paleocene  -​ Need to know the names of these phases -​ During pliocene phase, rainforests are turning into savannahs Fossilization -​ Those working specifically with fossils of primates, apes, and humans are known as paleoanthropologists -​ These bones and teeth can tell us how our ancestors moved, how big they were, what they ate, and what their mating and social structure may have been. -​ The plant and animal fossils found in the vicinity can be used to reconstruct the environments inhabited by our ancestors. -​ Burial is the key -​ Absorption of minerals and replacement of organic compounds -​ Hard materials fossilize more often (bone and ESPECIALLY teeth) -​ Soft tissues and behaviors rarely fossilize -​ There is an overestimate of the time of first appearance and an underestimate of the time of extinction -​ Oversimplify the relationship between fossil taxa -​ Underestimate divergence times -​ We’ve only found 3% of all species’ fossils The Principle of Superposition: If a rock strata has not been disturbed the lowest stratum was formed before the strata above it. (The bottom layer of rock is older than the layer on top of it.) Potassium-argon dating -​ 1.25 billion year half-life → we can look at the ratio of radioactive potassium to argon and give this rock a date if it’s younger than 1.25 billion years ​ Useful for older than 500,000 years -​ Volcanic rocks -​ Fossils not directly dated -​ Can date fossils millions of years old Biostratigraphy -​ We can look at multiple sites, if we know the ages of the layers of rocks in one site we can date the other sites’ rocks by associating them with the fossils of species we find in the rocks. Fossil record is biased… -​ Not everything fossilizes -​ Small animals are less likely to fossilize -​ Some habitats are less likely to create fossils -​ Savannahs are good for fossilization -​ Tropical rainforests are not because the soil is acidic and it breaks up organic material. -​ Primate fossil record is sparse because most live in tropical rainforests Evolution of primates Primate Characteristics to identify a fossil primate -​ Grasping hands and feet -​ Nails instead of claws -​ Forward-facing eyes encased in bone -​ Hind limb-dominated locomotion -​ Relatively large brain -​ Generalized teeth Evolution of early primates: Plesiadapiforms -​ Maybe not primates -​ No binocular vision -​ Small brain -​ Some nails, some claws -​ Grasping hands and feet in some -​ 65-54 mya (Paleocene epoch) Eocene: 40-50 mya: Origin of “true” primates Eocene Primates: Adapids and Omomyids -​ Earth warm and wet ​ Tropical forest spread into North America and Europe -​ Primates have evolved ​ Full suite of characteristics ​ Two families: adapids - like lemurs & omomyids - like lorises Late Eocene-Oligocene: 30-45 mya. Origin of Anthropoids  -​ African origin -​ New world & old world monkeys, apes and humans -​ Early anthropoids have been discovered in the Fayum of Egypt, Oman and Algeria and date from the Oligocene. -​ They were tiny How did monkeys get from Africa to South America? -​ Africa and South America were not connected 45 mya -​ Most likely hypothesis: animals traveled from Africa across the Atlantic Ocean into South America by rafting (giant chunks of land that break off and float across to South America) Miocene: 5 to 23 mya. Planet of the Apes -​ Warm and wet, became cool and dry overtime -​ In the early Miocene (22-17 mya) there was great diversity of fossil apes – more than 10 genera and 15 species known -​ Apes versus monkeys ​ Apes have no tail ​ Forelimb suspension ​ Short, stiff lower back ​ Mobile joints ​ Long arms and fingers Proconsul and Friends -​ Africa: 17-23 mya -​ Frugivorous -​ Forest environments -​ Apelike skull and teeth -​ Monkey-like postcrania ​ Quadrupedal, non-suspensory ​ But no tail -​ First feature that evolves for apes is probably the head Middle Miocene (10-15 mya) -​ Africa: Nacholapithecus and Kenyapithecus  -​ Asia: Sivapithecus -​ Europe: Dyropithecus, Pierolapithecus, Oreopithecus -​ Pithecus means ape -​ Don’t need to know these names ^ Oreopithecus aka Cookie Monster -​ 7-8 mya -​ Northern Italy in coal mine -​ Swamp habitat -​ Folivore; teeth different from any other ape -​ Need to know this name Sivapithecus -​ Looks like an orangutan -​ Dish face -​ Tall narrow orbits Gigantopithecus: really great ape! -​ China -​ Gigantopithecus giganteus/blacki: 300+ kg - bigger than gorillas! -​ Ate bamboo, like pandas? Apes disappear in Europe about 8 mya only apes left are in Asia and Africa Evolution of bipedalism -​ Belonging to subtribe Hominina i.e. creatures more closely related to humans than to chimps -​ Not to be confused w/hominids (African apes) What is unique about us? -​ We walk on two legs (bipedalism) -​ We have small canines and large molars with thick enamel -​ We have large brains -​ Very slow life histories and long juvenile periods -​ Overlapping offspring and cooperative breeding  -​ Talk and have elaborate symbolic culture Types of Bipedalism -​ Obligate: MUST do it; no other efficient choice -​ Habitual: can do it efficiently and ‘make a habit of it’ most of the time -​ Facultative: can do it if they have to What it takes to be a Biped: skull Foramen magnum placement is shifted, as a biped, head needs to be on top of the body so the foramen magnum comes from the bottom center of skull, not the back Spine -​ Lumbar lordosis: S-shaped curve in spine, allows the head, neck, pelvis, and knees to be aligned Pelvis Bipeds have a short, stout pelvis and the iliac blades face to the side * When we have a flat piece of bone, there is a muscle attached to it  -​ We have abductor muscles that join the femur to the wide flaring ilia -​ Stabilize the body when your weight is on one leg (like when walking) *Should be able to explain this on an exam Femoral Neck -​ Uneven thickness of dense cortical bone in the neck of the femur prevents stress on the femoral neck -​ Longer femoral neck is for abductor muscle attachment. -​ Top weight is pressing down on femur but we have this extra bone to support the extra weight Femur -​ Our legs (femoral shafts) are really long -​ Femur = thigh bone -​ We can take longer steps Knees and Feet -​ Knee ​ Bicondylar angle -​ Foot and ankle ​ Non-grasping big toe, we put pressure on our toes to push us forward ​ Arches Why bipedal? -​ We shifted from rainforest environment to woodland -​ In rainforest food is abundant  -​ Not in the savannah, have to travel for food Okay observations about why bipedal: -​ Feeding adaptation ​ Arboreal bipedalism, have to stand up and reach things ​ Ground feeding -​ Carrying and provisioning, have to carry a lot of food to feed babies Better observations: -​ Thermoregulation ​ Less solar radiation ​ Standing upright helps us regulate temp and not overheat because we have more wind hitting our body when we walk upright -​ Energetics ​ Bipedalism saves energy (calories) ​ It costs more energy to move your body around walking on all fours ​ Calories turn into babies → bipedalism favored by natural selection *chimps need to climb trees, this is why they don’t walk bipedally Earliest Hominins -​ 6-8 mya -​ Last common ancestor of chimps and humans 6-8 mya Sahelanthropus tchadensis -​ Chad, Africa -​ 6-7 mya -​ Hominin → we don’t know if it is an ape or hominin ​ Foramen magnum suggests bipedality ​ Chimp-sized brain ​ Small canines ​ Flat face; large brow ridge ​ Paper from 2022 suggests femur is more human-like and indicated bipedalism Orrorin tugenensis  -​ Kenya, Africa -​ 6 mya -​ Mix of woodland and savanna -​ Curved fingers suggest tree living -​ Hominin? ​ Femur suggests bipedality ​ Teeth chimp-like ​ Transition fossil between chimp-like ancestor and hominin Ardipithecus kadabba -​ Ethiopia, Africa -​ 5.2 - 5.8 mya -​ Hominin? ​ Toe bone suggests bipedality ​ Canine sharpens against lower premolar Ardipithecus ramidus -​ Ethiopia, Africa -​ 4.4 mya -​ Woodland habitat -​ Hominin? ​ Bipedal based on skull, pelvis, and foot ​ Climbing based on hand, foot, and pelvis ​ Small brain ​ Small canines ​ Short arms? Ardipithecus ramidus: Teeth -​ Incisors ​ Smaller than frugivore chimps -​ Molars ​ Thicker enamel than African apes; thinner than humans -​ Canines ​ Not sharpened ​ Not dimorphic Ardipithecus ramidus: hands -​ Hand: not knuckle walking -​ Foot ​ Grasping toe ​ Stiff foot for bipedalism -​ pelvis ​ Ilium adapted for bipedalism ​ Lower part apelike Class 12 October 23rd, 2024 1.​ Australopithecines 2.​ Early Homo and the first tool-makers 3.​ Homo ergaster and friends Early Hominins Sehalanthropus tchadensis Orrorin tugenesis Ardipithecus ramidus Chad, Africa Kenya, Africa Ethiopia, Africa 6-7 million years old 6 million years old 4.4 million years old All likely bipedal! Hominin Diversification Australopith Radiation -​ Small brains -​ Skilled upright walking, this tells us that we walked before our brains got big -​ Retain tree-climbing ability -​ Chimpanzee-sized with pronounced body dimorphism → males 2x as big as females -​ Reduced canine dimorphism -​ Large molars Australopithecus anamensis -​ Kenya and Ethiopia -​ 3.9-4.2 million years old -​ Grassy woodland environment -​ Bipedal: tibia (shin bone) → bipeds have a flat and wide top of the tibia -​ Long arms, shorter legs and curved fingers -​ Canines smaller than modern apes -​ Thick enamel on molars → enamel protects tooth from getting cracked Australopithecus afarensis -​ Ethiopia and Tanzania -​ 3-3.6 million years old -​ Woody grassland -​ Smaller canines, larger molars than Au. Anamensis -​ Slightly larger brain than a chimp (450 cc) -​ Bipedal -​ Body size dimorphism -​ Skull and teeth ​ More U-shaped dental arcade than humans ​ A smaller diastema compared to chimps  ​ Some dimorphism in canines ​ Molars more like chimps -​ Locomotion ​ Some tree climbing, based on scapula, fingers ​ Curved finger bones like chimps -​ Bipedal based on pelvis, footprints and feet (Lucy is Au. afarensis)  -​ Big toes of A. afarensis are more like humans than chimps (slide 13) -​ Dikika Child ​ “Selam” ​ Dikika, Ethiopia ​ 3.3 myo ​ 3 yr old female fossil found ​ Bipedal; tree climbing? ​ Hyoid: no language → bone in throat found called a “hyoid”, shape of hyoid bone is due to human language, the hyoid in this fossil is shaped in a way that proves it didn’t talk ​ Slower brain maturation (more human-like) → only about 75% of its brain was grown at 3 yrs old. Australopithecus garhi (garhi means surprise) -​ East africa -​ 2.5 myo -​ Cranial features: ​ Small brain (450 cc) ​ Sagittal crest ​ Large teeth -​ Postcrania: longer legs? -​ Stone tools? → only species associated with stone tools were genus homo Australopithecus africanus -​ South africa -​ Taung child  ​ Found in 1985 ​ Foramen magnum = bipedal ​ Small brain ​ Small canines ​ Challenged large brain first idea ​ This fossil was in the hominin line -​ Sterkfontein cave ​ First fossil named Mrs. Ples ​ Hundreds of fossils in this cave ​ Limestone cave formed close to a predator site, leopards make a kill and then drag it up a tree, bones fall from the tree ​ Lots of the fossils have canine marks on the skull, suggesting that they were food for various predators -​ More info about Au. africanus ​ 2.2-3 myo ​ Woody grassland ​ Cranially like Au. afarensis – bigger molars, smaller canines ​ Brains: ~460cc ​ Bipedal ​ Large size dimorphism (males 50% bigger than females) ​ Rapid tooth development ​ Teeth growing faster than brains ​ Large molars suggest crappy diet ​ Might need to grow teeth faster because once weaned off mother, need those teeth to eat food Austrolapithecus sediba -​ Malapa Cave, South Africa -​ 1.98 myo -​ Cranial ​ Small brain (420 cc); small teeth ​ Reduced musculature for chewing -​ Diet ​ Phytoliths: fruit, leaves, bark -​ Hand humanlike -​ Pelvis humanlike  -​ Arms relatively long -​ Thorax apelike -​ Foot primitive: suggests a unique form of bipedal walking (hyperpronation, walked on outer edge of its feet) Paranthropus: The Robust Australopiths Paranthropus aethiopicus -​ Kenya -​ 2.5 myo Paranthropus boisei -​ Hyperrobust -​ 1.3 myo -​ Kenya, Tanzania (Olduvai Gorge), Ethiopia -​ Ate seeds, tubers, roots -​ Nutcracker Man → had massive teeth and jaws for biting really hard food Cranial adaptations to nutcracker diet -​ Enormous back teeth -​ Sagittal crests ​ Large temporalis muscles -​ Huge cheek bones (zygomatic arches) -​ Postcranial: bipedal ^ Face designed like this so it doesn’t break when you chomp down on something hard  -​ Large temporal fossa creates postorbital construction -​ Not room for a big brain Robust vs. Gracile Australopiths -​ Robust premolars look like molars -​ Hugely expanded surface area of molars Paranthropus robustus -​ South Africa -​ 1-1.8 myo -​ Brain: 530 cc (getting bigger) -​ Cranial and dental adaptations for heavy chewing -​ Bipedal -​ Extended growth? → males kept growing through adult lives ^ Both trees are equally likely based on fossil evidence we have, we don’t know if afarensis or africanus is in direct line of homosapiens Early homo and the first tool-makers ​ Entering a cooling period about 1 myo, and we start to see periodic Ice Ages. Origins of Homo -​ 2.3 mya -​ Africa -​ Larger brains -​ Smaller teeth (molars) -​ Australopithecus limb proportions -​ Rapid development Homo habilis -​ 1.4-2.3 mya -​ East and South Africa -​ Brains ~600 cc -​ More rounded skull -​ Less prognathic face Taxonomic diversity or sex differences? -​ KNM-ER 1470 = Homo rudolfensis -​ Slightly larger brains The Origins of Tool Use -​ Tool use probably quite ancient -​ Apes use tools ​ Sticks to extract insects ​ Stone to crack open nuts ​ Sticks to test water depth -​ Homo uses tools often and begins making stone tools The Oldowan Tool Industry Mode 1. -​ Flakes, hammer, stones, cores -​ Simple tools associated with Homo habilis -​ Bang rocks together to make them Earliest evidence for stone tools -​ Old theory was it was only Homo habilis -​ Dikika (3.4 mya) - cut marks on bones that may be associated with the tools -​ Gona (2.5 mya) - first modified rocks (Au. garhi?) Oldowan toolmakers -​ Right handed -​ Suggests that they were engaged in hand-to-hand combat where right handed beings have an advantage Dikika cut marks ~ 3.4 mya -​ Cut marks made before the animal was fossilized -​ No stone tools found at this site Complex Foraging -​ Mode 1 stone tool technology ​ Carcass butchering  ​ Digging sticks -​ Swartkrans. South Africa bone tools ​ Termite, extractive foraging Meat Eating -​ Evidence for meat eating ​ Concentrations of butchered bones and tools ​ Bovid concentrations outnumber all others -​ Taphonomy: a study of what happens to bone after death ​ Tooths make broad smooth grooves and stone tools make sharp parallel grooves. -​ Olduvai ​ Not water accumulated ​ Some hyena dens ​ Hominins- cut marks *Cut marks do not necessarily mean hunting -​ Hominins too small and too poorly encephalized to hunt – a claim that Zarin doesn’t 100% buy because chimps hunted -​ Scavenging scraps from hyenas’ kills? -​ Probably both -​ Evidence that they might be both because some cut marks are on bones that hyenas would’ve eaten first had they killed that prey, other marks are on bones they would leave behind Central place foraging -​ Human universal, not found in primates -​ When did this begin in hominins? -​ Olduvai – 1.9 mya?  -​ Circle of stones → could this be a shelter? We don’t really know Home Life -​ Olduvai stone circle unlikely to be a home base -​ Carnivore activity -​ Limited processing of bone -​ Weathering of bone -​ Processing site for stone tools, this is where you go to butcher animals but don’t live there Homo ergaster and friends -​ Evolved from early Homo -​ 1.8 mya to 600 kya -​ Africa -​ Early Homo erectus (Asia not Africa) Skull -​ Primitive: postorbital constriction, no chin, receding forehead -​ Derived: taller skull, less prognathic, larger brain (900 cc - cubic centimeters), smaller jaws and teeth -​ Unique: brow ridge, occipital torus H. ergasters (Africa)/erectus (Asia) -​ More angular shape -​ Max breadth low H. Sapiens -​ More rounded shape -​ Max breadth high Postcrania -​ Long legs, narrow hips, barrel chest -​ Much taller than humans -​ Modern human body proportions -​ Reduced sexual dimorphism  -​ Language limited? -​ Terrestrial biped; runner? Tools and Diet -​ Acheulean industry ​ Mode 2 ​ ~1.5 mya ​ Biface (hand ax) ​ Specifically designed → carcass processing? ​ No change in tool technology for 1 million years, not an innovative species Meat Eating -​ KNM-ER 1808 (Kenya): Vitamin A poisoning from eating liver of animals -​ 1.6 mya -​ Hand axes plentiful -​ Cut marks on animal bones -​ Tooth anatomy -​ Had tapeworms → evidence of meat eating Questions about Homo ergaster -​ Language? -​ Hunting or scavenging? -​ Fire? -​ Cooking food? Class 13 October 30, 2024 1.​ Homo floresiensis 2.​ Homo heidelbergensis 3.​ Homo neanderthalensis 4.​ Homo sapiens ​ Fossil data ​ Genetic data The Australopithecines -​ Small brains -​ Skilled upright walking with a retention of tree-climbing ability -​ Pronounced body size dimorphism, reduced canine dimorphism -​ Reduced canine size, increased molar size -​ 42. Mya to 1.98 mya The Paranthropines -​ Skilled upright walking with a retention of tree-climbing ability -​ Robust face/skull with massive teeth for chewing -​ 2.5 to 1 mya Homo habilis/rudolfensis -​ Larger brain -​ Smaller molars -​ First habitual tool user -​ 2.3 to 1.4 mya Homo ergaster and friends -​ Evolved from early Homo -​ 1.8 may to 600 kya -​ Early Homo erectus  -​ Africa: Homo ergaster, Asia: Homo erectus Dispersal out of Africa -​ Dmanisi, Georgia -​ 1.8 mya ​ 5 skulls (brain 546-777 cc) ​ Could be an earlier hominin species? ​ Postcrania Homo-like ​ Oldowan stone tools ​ First evidence of hominins out of Africa Found skulls: Homo erectus -​ Discovered in 1891 by Eugene Dubois in Indonesia - called “Java Man” -​ 1.6 mya -​ Large brained (940 cc), bipedal -​ First fossil evidence for an ape-human transition species Homo erectus vs. ergaster Differences with H. ergaster: -​ Thicker skull -​ More massive face -​ More pronounced occipital torus and brow ridge -​ H. erectus has a sagittal keel (pointy head)  -​ Bigger, stockier body (cold adaptation) *Dmanisi skulls have a sagittal keel *Homo erectus in Asia until ~30 kya, used mostly mode 1 stone tools Homo floresiensis: “The Hobbits” -​ Flores, Indonesia -​ 11 individuals found -​ 16,000-74,000 years ago -​ Small bodied: ~3 feet tall -​ Small brained: ~400 cc -​ Sophisticated mode 5 stone tools Hobbit pelvis similar in size to australopithecines (Lucy) -​ The foot is almost as large as yours and mine, although 3 feet tall -​ Long toes -​ Midfoot like an Australopithecus or early Homo -​ Hobbit wrist is primitive, almost H. habilis or Australopithecus-like What is Homo floresiensis? 3 hypotheses: 1.​ Island dwarfism of Homo erectus? 2.​ Microcephalic Homo sapiens? 3.​ Ancestral lineage of early Homo? 1.​ Island dwarfism -​ Strange things happen on islands! -​ Small things get big -​ Big things get small -​ We know H. erectus was in Indonesia until 50,000 years ago -​ Do odd things happen to brains on islands? -​ Brains scale in predictable ways -​ To scale, Homo floresiensis should have a brain of 600 cc not 400 cc. -​ If to scale in proportion to brain, Homo floresiensis would be 1 foot tall  -​ This suggests hypothesis one is incorrect, brain should be bigger 2.​ Diseased Individual -​ If pathological Homo sapiens, it would be a disease that somehow mimicked early Homo or even Australopithecus postcranial anatomies → microcephaly -​ Would need to have a disease that made your brain small, but also changed your hand and pelvis into more primitive features, etc. -​ No disease known today that does this -​ Plus, Homo sapiens not in Indonesia yet 3.​ Ancestral Early Homo -​ Homo floresiensis is a surviving remnant from an earlier migration out of Africa by Homo habilis or even an Australopithecus? -​ This hypothesis “solves” the brain scaling problem, have brains in line with what we’d expect from an Australopithecine -​ But… where are the intermediate fossils between Africa and flores -​ And those stone tools… they made much more sophisticated stone tools than Homo habilis New discoveries: Homo heidelbergensis -​ Homo ergaster in Africa and Eurasia evolved into Homo heidelbergensis. -​ Larger brain (~1200-1300 cc) -​ Larger brow ridge -​ No chin -​ 1 mya to 400 kya -​ Through Africa and Europe -​ Used to be considered archaic H. sapiens -​ Now considered the ancestor of H. sapiens and H. neanderthalis -​ Adapted to the cold? → thick brow ridge is a sign of an animal being adapted to cold weather Toolkit -​ Large game hunting ​ Spears ​ Butchered animal bones -​ Diversity of food resources -​ Levallois prepared-core technique (Mode 3) European Homo heidelbergensis -​ 500 kya -​ 24 individuals -​ Sima de los Huesos, Spain -​ Cave system in Northern Spain -​ Features indicate these were likely proto-Neandertals -​ Genetics indicate more closely related to Neandertals than Denisovans Denisovans -​ 2010 discovery in Siberia, Russia -​ 41,000 kya -​ Also found in Tibet suggesting widespread -​ DNA from finger bone is distinct from H. sapiens and H. neanderthalensis -​ Not really sure what they are, a different species 5 species of Homo on Earth at 200 kya: Homo neanderthalensis -​ 200 kya to 40 kya -​ First found in 1856 in the Neander Valley about 10 east of Dusseldorf -​ First fossil hominin found The Neanderthal World -​ Fluctuating environment -​ Cooling tend -​ Eurasia ​ Frigid grassland ​ Many large mammals Neanderthal Anatomy -​ Large brain ​ Larger than Homo sapiens (up to 1740 cc) -​ Oblong skulls ​ Occipital bun ​ Big nasal cavity -​ Unique teeth ​ Taurodont roots (massive roots) ​ Heavily worn incisors -​ Short and stocky (30% heavier than Homo sapiens)  -​ More robust limbs with better developed muscle attachments -​ Wide torso -​ Short arms and legs Neanderthal Intelligence -​ Mousterian/Mode 3 tools ​ Finer, flake tools -​ Large game hunters ​ Bison ​ Red deer ​ Aurochs (wild cattle) ​ Adult prey -​ Buried their dead ​ Ceremonial? ​ Practical: keep scavengers away? -​ Personal ornaments ​ Necklaces ​ Body pigmentation Neanderthal language Could they speak like us? -​ Neanderthals have a hyoid bone that looks like modern humans and a human like version of the FoxP2 gene (associated with speech) -​ But perhaps it didn’t make the range of sounds that humans did. The Life of a Neanderthal -​ Short, difficult lives: arthritis, gum disease, injuries, conspecific care? -​ Lots of injuries, getting killed and very injured -​ Their injuries are similar to rodeo climbers Homo sapiens Homo naledi -​ Rising Star Cave, South Africa -​ 15 almost complete skeletons -​ Small brains (465-560 cc)  -​ Mixture of primitive and more human-like features -​ 250 kya The Origin and Spread of Modern Humans: Fossils -​ Homo heidelbergensis evolved into Homo sapiens in Africa -​ ~200,000 years ago -​ Less robust than heidelbergensis Oldest Homo sapiens fossils are African: -​ Ethiopia at 190 kya and 160 kya -​ South Africa, 100 kya -​ Middle East, 100 kya -​ Asia and rest of Europe: 40 kya What does it mean to disperse? -​ Slow process happening over thousands of years, not a big migration Homo sapiens: Morphology -​ large , round skull with high forehead -​ Small face and teeth -​ Protruding chin -​ Less robust postcranial skeleton -​ Long limbs Differences between Neanderthal and Homo sapien skulls Genetics -​ Homo sapiens evolved in Africa 90-300 kya -​ Small population left Africa 40-120 kya -​ Populated Australia and the Americas -​ Interbred with Neanderthals and Denisovans -​ Genetic data:  -​ Chimpanzees have more genetic diversity than humans around the world! -​ A random person from Africa and a random person from Europe are more similar than two chimps from the same place -​ Genetically, humans are very similar -​ As populations move farther away from Africa, genetic diversity decreases -​ Why? -​ Genetic drift can explain these population shifts Ancient DNA from Neanderthals and Denisovans -​ Denisovans and Neanderthals LCA 450,000 years ago (genetically distant) -​ Neanderthal/Denisovan and Human ~550,000-765,000 years ago (H. heidelbergensis?) -​ But… some interbreeding:  ​ Africans have no Neanderthal/Denisovan DNA ​ Europeans have ~2% Neanderthal DNA and no Denisovan DNA ​ Asians have ~2% Neanderthal DNA and 0.5% Denisovan DNA ​ Pacific Islanders have 2% Neanderthal DNA and 3-6% Denisovan DNA Class 14 -​ Homo sapiens tool kits -​ Eating cooked food: an adaptive obligation -​ Evolution of cooking -​ Cooking and the brain -​ Did we evolve to run? Homo sapiens tool kits Homo ergaster tools and diet -​ Acheulean industry -​ Mode 2 -​ 1.5 mya -​ Biface (hand ax) -​ Specifically designed -​ Unchanged for 1 million years The African Archaeological Record -​ Middle stone age (250,000 to 40,000 years ago) -​ Modes 3-5 -​ Mode 3: similar to, but more sophisticated than Neanderthal tools -​ Social organization: high density of humans move great distances -​ Symbolic expression: ornaments and other ritualistic behavior -​ Blades (mode 4) old as 250,000 and stop at 60,000 years -​ Microliths (mode 5) ​ Composite tools ​ Halfted into spears ​ Throwing sticks (atlatyls) Middle Stone Age -​ Bone tools (80,000-170,000)  -​ Heat-treated stone -​ Long-distance transport -​ Some evidence for simple shelters -​ Decorative carving -​ Engraved ostrich egg shells (60,000 years) -​ Engraved red ocher fragments Archaeological Beyond Africa -​ India and Sri Lanka -​ Australia ​ Occupied by 40,000 years ago ​ Cave paintings ​ Boats (~40,000) -​ Arctic Circle ​ 30,000 years ago ​ Sophisticated tools Upper Paleolithic Humans vs. Neanderthals -​ Higher population density -​ Longer lives -​ Healthier -​ Ritual burials (30,000 ya) -​ Art and music (36,000 ya) Eating cooked food: an adaptive obligation What is a hunting and gathering lifestyle? -​ H-G’s subsist on wild foods: -​ Gathered plants or hunted animals, including fish -​ No domesticated plant or animal food Why do we cook food if it’s biologically unimportant? -​ Raw food does not have many calories, have to consume a high amount quantity of food and spend a lot of time chewing -​ In Germany, they studied raw foodists, 50% of the women stopped ovulating → low fertility, bad reproductive success Solution: humans need cooked food for energy -​ Unique adaptation among wild animals -​ Critical dimension of the human niche Why can’t humans use raw food? 1.​ Humans’ molars are small 2.​ Humans’ guts are small Why is cooked food better? 1.​ Increases digestibility (% of nutrients digested) 2.​ Decreases digestion costs (energy expended) When apes were given the choice between raw and cooked food they ALL chose the cooked food. Evolution of cooking When did we adapt to cooked food? -​ Gelatinized starch grains were found in Neanderthal dental calculus -​ Fire controlled by at last 1 mya Let's use the argument of anatomy to explain this -​ H. erectus had small guts -​ N.B. large guts are needed for raw high-fiber diet -​ Going from big gut to small gut shows a dietary shift -​ The implication: somewhere between australopithecus and Homo erectus there was the control of fire because we see small guts and molars. -​ H. erectus also didn’t climb trees, they must’ve slept on the ground, this is dangerous without fire Cooking and the brain -​ Large brains have evolved independently in primates, elephants, dolphins and whales 3 primate advantages compares to other mammals: -​ Bigger brains (for our body mass) -​ More neocortex (for our given brain mass) -​ More cortical neurons (for given cortex mass) Neurons are costly! -​ Energy cost of brain depends on the number of neurons -​ 6 kcal per billion neurons per day -​ Animals pay much less than humans for brains, we have smaller guts so we pay less for guts *Humans chew for about 1 hour a day -​ Some time that would be spent chewing is now spent cooking Cooking came first and then came the eating of meat Did we evolve to run? -​ We need 50% more calories than australopithecines -​ H-G lifestyle requires a lot of traveling -​ Longer limbs means relatively lower cost traveling Persistence Hunting Hypothesis  -​ In the absence of sophisticated tools, Homo erectus could out-run an herbivore prey who would die of overheating before H. erectus → how they got food, how running adapted Running -​ A lof of features of human anatomy seem to be for endurance running and not simply walking -​ Long tendons and ligaments, short toes, arched feet, stabilized head, independently moving head and shoulders, sweat glands, and no fur -​ As we run, our hips and heads stay in the same vertical plane -​ Humans can run long distances at gallop speed! Cooling mechanisms -​ 581 kcal of heat are lost per litre of sweat -​ 5-10 million glands on your skin -​ Not efficient without fur -​ Animals cannot pant and gallop, but humans are open mouth breathers while running ​ Running is actually more energetically efficient than walking at a certain speed Class 15 11/3/2024 1.​ Human Genetic Variation 2.​ Geographic Variation in Human Skin Color 3.​ Natural Selection and Human Skin Color 4.​ A Brief History on the Biology of Race Human Genetic Variation Genetic Features of Homo sapiens -​ Genomes of humans, bonobos, chimps, and gorillas sequences -​ Only 1.3% difference between humans and chimps -​ But 71% of genes have differences between humans and chimps -​ Transposable elements and deletions -​ Synonymous vs nonsynonymous substitutions  -​ Synonymous would be all the alanine codons for example -​ Most differences between humans and and chimps are synonymous (~97%) -​ Remember some genes are pleiotropic (affecting multiple genes) and some are regulatory Regulatory Genes -​ Neoteny (delayed maturation) -​ Some genes that are expressed in the brain are turned on later in different species -​ Highly accelerated regions (HARs, ~3000) -​ Many HARs evolving rapidly in humans and do not code for protein -​ HAR1 regulates brain protein reelin, protein that helps us fold our brains which allows for higher surface area of the neocortex Human Variation -​ Humans vary in many ways -​ Physical appearance -​ Skills, preferences -​ Variation in human disease -​ *genetics are very similar, but expression is different Variation in Traits Influenced by Single Genes -​ Example: Huntington’s Disease -​ Runs in families -​ Pattern of inheritance consistent with dominant allele at single locus  -​ Occurs late in life so most people who have it don’t know until they’ve already reproduced and passed it on -​ Example: sickle cell anemia (single recessive gene) -​ Balanced polymorphism ​ Heterozygous individuals have highest fitness because some are resistant to malaria ​ Fitness tradeoff: some kids will be homozygous dominant (no resistance to malaria) and some will be homozygous recessive (will have sickle cell anemia), BUT heterozygous resistant to malaria ​ To have full sickle cell anemia, need two copies of the recessive allele ​ They’ve found there is a higher frequency of S (sickle cell) allele in regions with malaria Variation in Complex Phenotypic Traits -​ Many traits are influenced by many different genes  -​ Example: height, it’s a bell-curve distribution * It’s almost impossible for a single gene locus to control continuous variation so pleiotropic genes do Understanding Variation -​ Genetic and environmental factors contribute to variation Twin Studies -​ Monozygotic (identical) -​ Dizygotic (fraternal), genetically related to each other as full siblings are -​ Genetic traits should be more similar in monozygotic twins than dizygotic -​ Identical twins are more similar to each other in height than fraternal because height has a strong genetic component *there are also outside factors that affect height Skin color in humans is an example of polygenic inheritance Geographic Variation in Human Skin Color -​ Most darkly pigmented people live at the equator, most likely pigmented people at the poles, has to do in some ways with the intensity of the sun -​ Darwin rejected correlation between skin color and geographical location  -​ Avicenna (Egyptian philosopher) believed that there was a relationship between the intensity of the sun and skin color AND a relationship between the sun and the temperament of the people who live close to it. -​ Samuel Stanhope Smith thought that the graduation of color holds a more regular progression according to its latitude from the equator What is the ancestral color of humans? -​ Skin doesn’t fossilize -​ We have to use the comparative method -​ Chimps have black fur but light skin -​ Homo erectus/ergaster -​ Modern human body proportions -​ No hair on skin because they had sweat glands -​ It is hypothesized that our ancestors had dark skin -​ MC1R melanocortin 1 receptor (MC1R) locus makes a protein that affects the color of skin and hair. -​ Comparison with chimpanzee genome suggest that the human variant appeared 1.2 million years ago. Natural Selection and Human Skin Color Probably has most to do with UV Radiation -​ Lots of UVA and some UVB radiation gets through at equator -​ At poles, almost no UVB gets through in winter months -​ 86% of total variation in skin color can be accounted for by ultraviolet radiation Why do we need UV protection? -​ Hypothesis 1 (wrong): UV radiation causes damage to DNA and causes skin cancer, increasing mortality -​ Its like Huntington’s in the way that skin cancer will kill you after you’ve reproduced and passed on your genes for light skin, doesn’t make sense -​ Hypothesis 2: UV radiation affects folate metabolism causing birth defects, negatively affects reproduction and therefore fitness -​ People with darkly pigmented skin have melanin (2 kinds) -​ Melanin absorbs UV energy How can we explain this variation? -​ When UVB hits your skin it triggers the synthesis of vitamin D -​ Individuals with lightly pigmented skin can make 5-6x more vitamin D than someone with darkly pigmented skin -​ Vitamin D deficiency results in defective calcification of bones, and affects immune function and cell growth What about the Inuit? -​ Brown skin helps protects against UV that reflects off of the snow and water -​ They obtain vitamin D from meat in diet Depigmentation evolved more than once -​ Studies have shown that mutations in diff genes result in the lack of pigmentation in Europeans and Asians -​ This is an example of convergence -​ Dark pigmentation evolved more than once too, in India and Africa, etc. -​ At least 120 genes have been identified for pigmentation -​ Current and historic voluntary and involuntary migration result in a lot of people living in regions to which they are not adapted -​ Urban living is also a mismatch → wearing clothes to color skin, staying inside, etc. A Brief History on the Biology of Race -​ Skin color is a poor identifier of human groups or races -​ Most skin color genes are inherited independently with traits for face shape, eye color, hair color/texture -​ Traits don’t travel in packages associated with races -​ Race is NOT a biological concept it is a CULTURAL one -​ There is variation in skin color based on geographic distance but it’s a continuous line not clustered into 4 different categories (european, african, asian and south indian) *If race was biological we would expect black portuguese people to be more similar to people in west africa (sao tome) and white portuguese people would be similar to those in portugal. This graph shows this is not the case at all. -​ Linnaeus classified people into four different racial groups: White Europeans, Red Americans, Brown Asians, Black Africans -​ Kant convinced Linnaeus to include temperament to his theory on race -​ Kant imposed a hierarchy on races -​ Believed that humans had different capacities for developing civilizations based on their distance from the sun  -​ Cartwright wrote that the white species had qualities black species didn’t. He was a doctor so he had a high influence. Said that black people who wanted freedom had a disease Race may not be biological but it affects our biology -​ black women having babies and 3x the mortality rate as white women having babies, this is because of systemic racism -​ Bias based on race is based on cultural tradition, taught to us as kids -​ When kids are asked to pick a playmate they don’t care about race, only care that they speak the same language Class 17 November 20, 2024 1.​ Family Structure 2.​ Homosexuality Family Structure Foraging societies/ hunter-gatherers -​ Ethno-linguistic unit ​ Share values and beliefs, language, territory, ethnicity, etc. ​ 500-1000 people in units of ~30 ​ Generally not stationary -​ Foraging societies not found in any other primates besides humans -​ Marriage is typical -​ About 10-20% of men have more than one wife (polygyny) -​ Lots of cross-cultural variation in whether married couples stay with maternal, paternal kin or both Pair Bonds -​ When human groups accumulate wealth, there is an increase in polygny -​ Females bonded to one male -​ Pair bonds (at least from female perspective) -​ Polyandry is rare Foraging societies: affinal kinship -​ Refers to kinship through marriage -​ Band composition reflects overlapping connections and complex social networks -​ Most ppl don’t live with primary kin -​ Interact with ~1000 people in your lifetime -​ Kinship organizes a foraging society’s social world -​ Kin can mean different things to different people -​ Because of pair-bonds providing paternity certainty, we can track both maternal and paternal kin -​ Crow-type: maternal kin, omaha type: paternal kin Kinship and Food Sharing -​ Food sharing among the agta of the philippines and the mbendjele of central africa -​ Kinship and reciprocity/need impact food distribution Homosexual Behavior -​ Documented in at least 450 different species Possible function of sexual interaction: -​ Conception -​ Paternity confusion -​ Practice -​ Communication Practice -​ Copulation mechanics/social skills -​ Chimps - infant males intromit w/females including their mothers -​ Baboons - juvenile males mount females (and males) Communication -​ Bonobos have 543 behaviors -​ 79% shared w chimps -​ 6% unique to bonobos  -​ Almost all of these have to do with genitals -​ Female-female sexual interactions are an important pathway to: 1.​ Reducing tension from feeding competition, conflict, ect. 2.​ Integration of an immigrant female into new community Female-female sex names: -​ GG-rub -​ Genito-genital rubbing -​ Hoka-hoka Homosexuality as an alternate strategy -​ Female homosexually mated pairs: -​ Widespread in colonies -​ Couples unrelated; cooperate -​ Result of excessive females -​ Mate with several males -​ Rear own young -​ RS higher than lone females, lower than female + male -​ Bachelor groups of adults and adolescents: -​ Older males treat younger males like females -​ Copulations -​ Sexual dyads that resemble pair-bonds -​ Older males compete over access to younger males *theres a bias against homosexual sex because it is not for conception and therefore “unnatural” and a sign of sickness Warfare and Cooperation 1.​ Chimpanzee Between Group Aggression 2.​ Reconstructing the LCA 3.​ Human Warfare 4.​ Self-Domestication Human nature: Hobbes - humans naturally aggressive Rousseau - humans naturally peaceful Chimpanzee Between Group Aggression -​ Most primate groups are surrounded by other groups (enemies) Two Types of Between Group Aggression 1.​ Balance of Power (mutual fear of intense aggression) -​ Begins with a strong attack -​ Escalates rapidly -​ No need to stop when opponent stop fighting -​ Victims can die if the power imbalance is large -​ Rare in the animal world -​ Multiple aggressions = raid 2.​ Balance of power -​ Begins with mild threat -​ Escalates slowly if at all -​ Dangerous to attack ferociously -​ Best to stop when opponent stops -​ Both fighters survive -​ Multiple aggressors = battle Imbalance of power hypothesis Ecology → fission fusion grouping (if one chimp is wandering around by himself, they are at risk) → imbalances of power (if you’re a baboon, no fission fusion, never alone) → low-cost lethal aggression → Increased inter-group dominance → increased access to resources + mates Prediction 1: Power asymmetry between opponents provokes attack -​ Males in small parties avoid territory edge (border zone) Prediction 2: Power symmetry suppresses attack -​ Prolonged interactions -​ Mutual call, display, charge; little to no contact -​ Repeated individual retreats and approaches -​ High tension; much coalitionary behavior  -​ Ends in one or both parties withdrawing Prediction 3: Victims of aggression tend to be male This suggests males are trying to kill rivals Prediction 4: Inter-group dominance → resources -​ Ngogo chimps: ​ Raiding results in more > 20 kills ​ Chimps occupy areas where kills occur Reconstructing the LCA Data suggests that LCA was more chimp-like than bonobo Did our LCA kill each other or were they nice to each other? Clues from morphology: comparing bonobos and chimps -​ Bonobos are scrawny version of chimps -​ Bonobos have smaller canines -​ Bonobos have smaller heads, they are paedomorphic (childlike) in their crania for their given body size. -​ If you grew a chimp you’d get a gorilla, if you grew a bonobo you’d get a weird looking gorilla with a small head -​ This tells us that body proportions of LCA were more chimpanzee-like -​ Bonobo morphology is evolutionarily derived Is bonobo behavior derived as well? Lack of aggression, lack of killing -​ Paedomorphism and reduced aggression -​ Reduced aggression linked to cranial reduction, paedomorphic crania, limb gracility, and dental reduction Self domestication? Human Warfare -​ Fry believed that war was not a natural, inevitable, part of human nature -​ Semai people, Malaysia, very peaceful, people kill them, they never kill – don’t have the resources to fight back so they flee -​ State-level societies are more likely to engage in warfare because they have the resources Nomadic foraging societies are often… -​ Neighbored by farmers -​ Politically and militarily weaker than farmers -​ Peaceful -​ Indicates that a tendency to warfare is adapted to context Foragers surrounded by other foragers are more prone to warfare -​ Sometimes in this case, live in a state of constant warfare -​ Social organization: ​ Networks (~2000) of families (~15-40) ​ Distinctive dialects and clothing ​ Specific territories ​ Intimate knowledge of territory  -​ If they see a stranger w/out their clothing, they generally kill them Inuit/Yup’ik War Tactics -​ Block door and throw torches inside -​ Kill anyone trying to get out -​ Almost always in autumn (good food, goof light) -​ Sometimes walk long distances to raids Success and survival depends on: -​ Strength in numbers -​ Trust that other raiders will not defect *The more cultural rewards, the higher the mortality in warfare. -​ Annual death rate in small-scale societies is not that different than chimps -​ Within group aggression, chimps are awful to each other but humans are really nice to each other -​ Chimps are 100-500x more aggressive than humans within a group -​ Humans are aggressive abroad and peaceful at home Class 18 - Guest Lecture 1.​ What are the definitions of shaman/shamanism and is it ubiquitous? What are features of shamanism that are universal across cultures? Two types: Sikerei: Healers of Mentawai: see spirits, entry is regulated, dramatic initiations, trance; specific taboos apply Simata: less developed Shaman: practitioner who uses trance to provide services, e.g. healing and divination -​ Is ubiquitous Common features of shamanism across cultures: -​ Trance -​ Dramatic initiations (death and rebirth, etc.) -​ Chanting, drumming, dancing -​ Displays (fire, etc.) -​ Costly prohibitions (sex, food, social isolation) -​ Peculiarity (epileptic, additional fingers, immaculate conception, etc) 2.​ What is the definition of trance and what are some of the behaviors that might be observed during trance state? Trance: temporary state that appears psychologically and behaviorally distinct from normal human functioning Behaviors: -​ Violently shake or incredibly still -​ Act like a demon -​ It’s a demonstration of strangeness to separate the shaman from normal human beings 3.​ What is the subjective model of shamanism? (You should be able to describe the three components of the model) Shamanism adapts to beliefs and cognitive architecture: most plausible means of controlling uncertainty 1.​ Humans have a psychology of superstition → we rely on erroneous explanations for random events (healing illness, doing well on exams, change in weather, etc.) 2.​ Because of our reliance on erroneous explanations, there is a selective retention of intuitive magic → specialists compete in this market, has the power to spread because we place so much validity on it, shamans are popular, more people want to become shamans  3.​ Then there is a transformation into entities distinct from humans to claim special powers → we are predisposed to believe invisible forces control events, shamans influence events by interacting with invisible forces, people attribute superhero abilities to people who diverge from normal humans (extra finger, immaculate conception, etc.) 4.​ According to cultural evolution, what is the function of culture? You should be able to articulate the idea of subjective cultural selection. Subjective cultural selection -​ Humans have goals & they selectively retain variants subjectively evaluated as satisfying those goals & culture is a technology that has evolved because it appears to be the best way to achieve goals 5.​ How does self-denial or how do taboos manifest among shamans? And what are the functions of these taboos? 1. Taboos on Shamans: -​ Permanent dietary tools -​ Some sex taboos 2. Are they costly? -​ These are valuable foods 3. What do people infer from the costly self-denial, 3 hypotheses: -​ sincere belief, more cooperative, more supernatural, more powerful Class 19 - Culture and Language 1.​ What is culture? + definitions 2.​ Do animals have culture? 3.​ Human culture variation 4.​ Social learning 5.​ Shamanism What is culture? -​ Language -​ Norms or behavior -​ Dress and appearance -​ Tools  -​ Technology Culture: “Information or behavior acquired from conspecifics through some form of social learning.” -Boyd & Richerson 1996 -​ Distinct from genetic info -​ Social learning -​ Variation across groups Memes: An idea, behavior, or style that spreads from individual to individual within a culture. Tradition: Enduring behavior patterns shared among members of a group that depend to a measurable degree on social contributions to individual learning (Fragazy & Perry, 2003) Do animals have culture? How ethologists recognize culture: behavioral variation among populations that cannot be explained by genetics or ecology. Cultural variation in nature Ex #1: Food processing traditions in Japanese Macaques -​ Monkeys provisioned on beach -​ Female macaque named Imo invents potato washing to get rid of sand -​ Monkeys are watching and adapt behavior -​ Behavior spread along kin lines -​ Behavior spread very slowly -​ Now a cultural tradition Ex #2: Food processing traditions in Black Rats -​ Didn’t know how to eat pine cones -​ Some mother’s figured out a technique to get seeds in pinecones -​ Babies of moms who knew how to do it learned how to do it -​ Not genetic, swapped biological children, found it was a learned skill -​ Now this is a cultural thing across all these rats Ex #3: Wake up times in meerkats -​ Meerkats live in dens -​ Some dens like to sleep in, others wake up early  -​ There is genetic overlap across these dens so it’s not genetic -​ It’s also not explained by seasonality -​ Explanation: when a meerkat immigrates the meerkat wakes up, everyone still sleeping, meerkat goes back to sleep Ex #4: Trust games in Capuchins -​ Two capuchins sitting together, to prove friendship one capuchin guides the second one so their finger is behind their eyeball and holds it there for about 5 minutes but can last an hour! -​ No gene, this is culturally learned Chimpanzee culture -​ There’s a lot of variation in behaviors across different groups of chimps, not all of these are explained by genetics or ecology so it’s assumed it’s because of culture -​ Termite fishing was thought to be cultural but might be biological because some sites don’t have the type of termites chimps like to eat -​ Hand clasp grooming: varies by chimp groups, some do it many times a day, some once or twice a year, some never -​ Palm-palm contact varies by matriline (in humans), this is a hint that this behavior is learned Human Cultural Variation Ex #1: The Neur/Naath and the Dinka -​ Behavioral similarities: ​ Similar language group ​ Lived in seasonal swamp ​ Raised cattle and grew millet and sorghum -​ Nuer territory expanded to take over Dinka territory -​ Why didn’t the Dinka take over the Nuer territory? -​ Among the Nuer/Naath, cattle production was geared for exchange (had to give cows to get married) rather than subsistence -​ For Nuer it was more essential to have big herds of cows because that’s how you got married → more motivation to have more land → more drive to take over territory Ex#2: German vs. Yankee Immigrants in Illinois -​ Sonya Salamon studied farming communities in Illinois settled in mid 1800s by immigrants from dif regions: germans and yankees -​ Carefully matched for soil type and other factors that affect farming practices -​ Collected data on farming behavior, etc. -​ Did in-depth interviews in each community Yankees express “entrepreneurial” values -​ Farming is a business -​ Goal: make money -​ Place high value on education -​ Don’t pressure children to go into farming Germans expressed “yeoman” values -​ Farming is a way of life -​ Goal: keep farm in family -​ Don’t place high value on education -​ Urge children to go into farming * German descendents replaced yankee descendents in terms of owning the farms What is unique about human culture?? -​ If we were transported to a random place, say Canada (-50 degrees), we would need warm clothing, shelter, light, water, food, etc. -​ We would probably die -​ The Lost Franklin Expedition of 1845, two ships set off from England, led by John Franklin, 1847 their provisions ran out, 1848 they started hiking through Canadian arctic, they all died, they didn’t learn to hunt, make clothes, etc. in the wild. Human culture accumulates! -​ We can engage in behaviors more complex than what an individual could do on their own. -​ We innovate behaviors based on what others are doing  -​ Ex. we went from writing on paper to typewriters to desktops to laptops → accumulated culture -​ Ex. chinese fishing boats -​ Could we build a toaster from scratch? Probably not -​ Cumulative culture allows us to disperse → we don’t speciate in new habitats, we adjust and accumulate culture, we innovate solutions to external problems -​ This means when we go into new habitats we don’t need to biologically evolve, just have to culturally evolve Social learning Three main transmission paths: 1.​ Vertical -​ Parent to offspring 2.​ Horizontal -​ Among peers 3.​ Oblique -​ Old to young Genetic evolution happens when you have babies, slower than cultural which happens everyday Mechanisms of Social learning 1.​ Social Facilitation -​ An animal indirectly increases the likelihood that another individual will learn the behavior on its own -​ Great tits (birds) open milk bottles, they didn’t watch the others open the bottle, they figured out how to open the bottle on their own each time -​ Social facilitation is that one tit showed everyone there were bottles there but each tit learned how to open it on their own 2.​ Observational learning -​ Watching someone solve the problem and that’s how you learn to solve it. -​ Ex. termite fishing in chimps -​ Females spend more time watching their moms termite fish than males -​ Females end up much more able to use tools than males because they watched their moms 2a. Imitation -​ Humans good at observational learning, especially imitation -​ Human beings expect to be taught so they will imitate very exactly, chimps don’t teach each other so they will imitate but not as precisely, they will also use their intuition 2b. Goal Emulation -​ An animal observes the final outcome of another individuals actions and copies the outcome, not the whole sequence of events -​ This is what chimps do but not humans, they imitate 3.​ Teaching -​ Active involvement of experienced individuals in facilitating learning by naive conspecifics (subjects) -​ Meerkats: the first wild mammal in which teaching was convincingly shown -​ Meerkats must learn how to catch and eat scorpions -​ Meerkat adults remove the stinger of scorpion, bring back live but harmless scorpion to pups so they can learn how to deal with a live scorpion -​ Then later they bring the pups a scorpion with a stinger so they can learn how to remove it themselves Criteria for teaching: 1.​ A modifies its behavior only in the presence of B 2.​ A incurs some cost or at least does not obtain an immediate benefit 3.​ B acquires knowledge or learns a skill earlier in life or more rapidly or efficiently than it would otherwise do if it was not taught Humans learn from different people depending on what life stage they are in -​ In childhood most adults are good teachers because we are learning general things -​ In adulthood we learn from experts because what we’re learning is more specific What about language?  -​ Language is a part of our culture but it is what allows us to have accumulative culture -​ We can communicate and store information across generations Culture is part of our biology -​ Culturally acquired beliefs are deeply intertwined with the physiology of brains, hormones, etc. ​ E.g. differences in attitudes set off a cascade of physiological differences in Northerners and Southerners → “the asshole bump” study Class 20 December 9, 2024 1.​ Evolution of language 2.​ Mismatch disorders 3.​ Recent human evolution 4.​ Some final thoughts Evolution of language -​ Allows for cumulative culture and social learning Early views of animal communication: -​ Displays and signals reflected emotional state of animals -​ Vocalizations involuntary Are animals using sounds in an intentional way? Results from trial: -​ Chimps produce waa barks and alarm hoos when a friend was present compared to a non friend (so they are only warning a friend or relative of the snake) -​ More likely to look at another individual before giving waa bark and/or alarm hoo (not true for soft hoos) -​ 75% of individuals alternated their gaze between the snake and the arriving individual while calling  -​ Individuals were more likely to stop calling when others indicated they know snake is there Is vocal communication in chimps intentional? (5 criteria) 1.​ Do chimps understand the thoughts of others? 2.​ Is the signal directed at a recipient (is there an audience)? 3.​ Is the signaller sensitive to whether or not the recipient is paying attention? 4.​ Does the signaller alternate his/her gaze between the stimulus and the signaller? 5.​ Does the signaller persist until the recipient indicates he/she has the knowledge? In an experiment… -​ Kanzi could understand 72% of novel sentences -​ Chimps and bonobos can understand but not produce grammar What makes humans special in terms of language? -​ We make sentences using grammar. -​ Languages are translatable into one another with good efficiency -​ Some capacity for language acquisition seems to be innate -​ The holy grails of HUMAN language are the emergence of SYNTAX (rules about the structure of sentences) and RECURSION (phrases within phrases) -​ We also have a language for numbers which allows us to have long-term reciprocity → “I’m gonna give you $4 but you’re gonna owe me $4.25 tomorrow” FOXP2 gene -​ The ‘language’ gene -​ In the KE family in the UK, 16 members have either missing copies of the gene or mutations in the gene -​ Mutations affect the articulation of speech as well as upper body coordination, some manual dexterity, and some aspects of grammar production. Mismatch disorders -​ Humans have lived in industrial environments for a tiny amount of time in evolutionary history  -​ Our bodies are adapted to a much different environment than that which we now live -​ Humans behavioral flexibility allows for rapid adjustments to new conditions, but genetic change takes generations Mismatch disorders: 1.​ Obesity ​ Rates of obesity have increased dramatically over the last two generations ​ Well-known health consequences ​ Why is this trait not selected against? ​ Predisposition for obesity is inherited but not obesity itself ​ Rare in other species ​ Ability to store fat and a preference for high calorie foods has been adaptive during most of human history ​ Energy abundance would have typically been temporary and associated with high workload ​ Weak selection on things that happen after reproduction 2.​ stress ​ Stress is an adaptive response to a crisis ​ Fight or flight ​ Main effects are to increase blood flow and energy available to major muscle groups ​ Response is nearly identical across animal species ​ The response is identical regardless of the type of stress: cold, heat, low energy, predator, psychological=perceived crisis ​ Humans are unique in that we may have stress responses to events in the past or in the future ​ In industrialized cultures, stressors are less related to basic survival functions ​ Frequent or prolonged stress leads to a variety of negative health outcomes ​ Stress has short-term adaptive effects but long-term negative effects; in the moment stress response is good as it helps us avoid danger but in the long–term too much stress can have negative effects on our health  ​ If stress was an accurate indicator of poor conditions during our evolutionary past, it may be a good cue for delaying reproduction ​ One common cause of stress is a lack of social support, which was often associated with conscious delay or reproduction; if you are stressed it’s probably a bad time to bring a child into the world so stress might purposely delay reproduction (no evidence of this?) ​ Instead the reason is that stress stops people from wanting to have sex, this is why people are less likely to conceive when stressed 3.​ Reproductive cancers -​ All factors associated with an increased number of menstrual cycles -​ Hunter-gatherers experienced 50-80 menstrual cycles compared to ~400 in U.S. -​ More menstrual cycles leads to greater estrogen exposure -​ During each cycle, high estrogen levels at the time of ovulation lead to cell division in the breasts -​ Most cancers are caused by an accumulation of mutations during cell division -​ Industrialized humans have more cycles and higher estrogen and therefore more risk of breast cancer  -​ Many in western populations have high testosterone -​ Testosterone acts on growth and maintenance of the prostate in an equivalent way to estrogen and breast tissue Summary -​ Changes in life history in industrialized cultures are directly related to a number of fitness-reducing disorders -​ These are related to a disconnect between our biology, which is adapted to environments of resource scarcity, and our modern environments of resource abundance -​ In some cases, however, understanding the evolutionary basis of these traits leads to a better understanding of prevention Recent human evolution *evolution occurs when allele frequencies change in a population Example of lactase persistence came up again so fair game for exam (more detailed on the slides) Starch and Amylase -​ The origin of agriculture also increased the amount of starch in our diets -​ Amount of starch varies by population -​ When your mouth detects starch it releases amylase. Amylase breaks starch into sugar. Process starts in your mouth when you chew  -​ Some people have more copies of the amylase gene than others, more copies means more amylase production. -​ People from high starch populations have more copies of amylase gene -​ Amylase helps increase digestive efficiency especially when challenged with diarrhea -​ New study suggests that this really took off with agriculture Greenland Inuit: Diet and Height -​ Inuit have a diet high in polyunsaturated fatty acids -​ In GWAS (genome wide association studies), compared to Chinese (Inuit come from China) and European (living in greenland) populations, Inuit show a different variant in the FAD (fatty acid digestion) genes (they are TT instead of GG) -​ These genes are related to breaking down fatty acids -​ Mutations to FAD genes in Inuit also affect growth -​ These mutations affect height and weight -​ Each derived allele reduces height 0.66 cm and weight 2.2 kg Some final thoughts What makes humans special? -​ Our locomotion -​ Our brains -​ Our tools and culture -​ Out language