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BIO 133 Zusammenfassung.pages
BIO 133: Anthropologie Questions Who are we? We are primates (great apes), relatives of Dermoptera (Riesengleiter)! Where do we come from? Africa! ! Primates • a rather unspecialized (‘primitive’), small to mediumsized mammal! • mobile digits with nails (rather than claws)! • with an emphasis on vision relative to smell ! • with forward-pointing eyes, stabilized by the postorbital bar! • with larger than average brain size! • which lives longer than average! • Radiated after mass extinction 65 Mya! • Live primarily in warm areas with forests! ! ! ! Most great apes died during the Messinian crisis, as forest were sparse. The only surviving species relied less on trees and more on the ground. Monkeys (smaller, less arm movements) became more dominant afterwards.! ! Evolutionary classification (phylogenetic) vs. cladistic. Humans as family Hominidae vs. part of Pongidae family.! => correct is hominins, not hominids! ! Written by Joel Lüthi, artwork from ppts! 1/23! HS 2013 Hominins • First specialization of hominins was bipedalism (not larger brains)! • Genus Homo emerged around 2.5 - 2 Mya! • Bipedalism, larger brains, smaller teeth, stone tools! • Modern humans: last 10‘000 years! • Domestication of plants & animals! ! ! • Civilization (cities, states, writing)! How evolution works Complexity: Arises from natural selection & adaptation (trait which has evolved for a particular function or trait that gives owner fitness advantage)! • Variation, which is heritable! • More offspring than survivors! ! ! ! • Non-random survival & reproduction! => Adaption! • Sometimes leaps happen (endosymbiosis, macromutations, mass extinctions), but most changes are gradual (development of the eye: growing light sensitivity confers advantage etc.)! ! • Without predefined goals!! Cope‘s rule: Body size in a lineage increases with time (generally true, because increase in body size brings many advantages)! ! Marsh‘s Rule: Relative to body size, brains show growth over evolutionary times (generally true)! ! Diversity: Phylogeny/historicity (once a change is made, going back won‘t happen)! ! ! • Once a certain point is reached, constraints apply. Local optima! Written by Joel Lüthi, artwork from ppts! 2/23! HS 2013 Defining Humans Russian dolls/historicity: Subdividing groups with new derived features => Humans are mammals, primates, anthropoid primates, great apes, humans.! ! Mammalian synapomorphies! • Reproductive features: Internal fertilization & lactation! • Heterodontism: Different teeth, stronger jaws, more divers diets! • Physiology: Active life style, high metabolic rates! • Homoiothermy & endothermy:! • Higher growth rates (with increased risk if energy is sparse)! • Larger brains! • Larger & more complex brains: ! • Basal ganglia & brain stem are the oldest parts of the brain, regulating instinctive actions.! • Paleo-mammalian brain is the limbic system, regulating innate & learned social responses, maternal behavior and play! ! • Neo-mammalian brain is th neocortex, having declarative knowledge about the world based on sensory analysis.! Primate synapomorphies! • Vision: Eyes are protected by post-orbital bar or „Augenhöhle“ (=> stable while chewing), forward facing (better vision than smell)! • Hands: more sensitive & flexible, can handle branches & food really well. Have nails instead of claws. Predisposition to tool usage.! • Life history (life cycle & its timing): Primates grow slower than other mammals, have longer gestation, lactation, later age of first reproduction, lower mortality rates, longer life spans (animals in trees live twice as long as terrestrial animals). Is driven by Tradeoffs & reflects unavoidable mortality imposed by ecology! • Large brain compared to body size: The longer the life span, the bigger the brain.! ! ! ! Written by Joel Lüthi, artwork from ppts! 3/23! HS 2013 Anthropoidal synapomorphies! Anthropoids: Monkey & apes! • Strongly vision oriented! • diurnal (day instead of night)! • larger brains, slower development! • young mostly singletons, precocial (born quite mature) & carried:! • Compare to caching youngs: Place them somewhere, come back with food! • Carrying allows for greater range, nomadism! • Slow postnatal development => vulnerability to infanticide! • Long lactations leads to a break between the birth and the conception of the next child (to avoid overlapping lactation times) => risk of infanticide (as this would shorten the gap)! ! => strategies to reduce infanticide risk: Male-female association! • always in mixed-sex groups, complex social life with facial expression & signals. Anthropoids are able to recognize other individuals and establish hierarchies! ! Great apes synapomorphies! • Larger brains, increased cognitive skills:! • Self-recognition, self consciousness and Theory of Mind! • Nests building! • Tool use & ability to make their own tools! • Learning abilities! • Imitation and emulation (social learning)! • Slow development, low reproductive rates, long life span! • High social tolerance: Food sharing & cooperation with non relatives! ! Human hunter-gatherers! • Hypercooperation: Obligate food sharing, no leadership, collective action (warfare)! • Life history: Longer lifespan, slower development, midlife menopause, but a higher birth rate & fatter babies! • Socio-sexual: pair bonds, sex in private! • Culture, technology & language! ! Written by Joel Lüthi, artwork from ppts! 4/23! HS 2013 Our anthropoid core Group living & group life • Beneficial for predation avoidance, but problematic for food competition => The group is bigger, the higher the predation risk or the food supply.! Competition & dominance • Scramble: power or aggressivity does not increase the food you get, e.g. when small parts need to be collected => enforced equal sharing The bigger the group, the stronger the scramble! • Contest: The more powerful you are, the more you get, e.g. distribution of a large prey.! • Dominance: saves the cost of repeated escalation. Works only when individuals recognize each other, are subjected to repeated interactions and possess memory. Dominance is always a feature of a relationship, not an individual. Within groups, it is spatially & context independent! • Dominant individuals possess higher fitness, increased reproductive success! • The bigger the group, the bigger the range needs to be => increases scramble & limits group size! • Unless there is migration, groups normally grow above optimum! ! Cooperation & altruism • Primate groups are highly cooperative! • Nature never favors true altruism (but paybacks can be indirect). Indiscriminate altruism is evolutionarily unstable! => Reciprocity or mutualism! • Risk of defection when helping non-kin! • Mutualism works, especially with bigger groups.! • Dyadic cooperation work if there are frequent interactions, individuals can keep track and contingency (only help those that helped you as well) => Monitored friendship: Emotional book-keeping (in humans some contingency, bookkeeping for people we don‘t know well)! • Signaling & male behavior: E.g. increase male vigilance for predators => gains trust of females, reputation! • Kin selection according to Hamilton‘s rule. But how do you recognize your kin?! • Spatial distribution: Whoever is encountered at specific place, e.g. my nest! • Familiarity rule: This is how primates do it! Kin is whoever has become familiar during early life! • Phenotype matching: kin is whoever matches a template (works for insects, certain vertebrates)! Written by Joel Lüthi, artwork from ppts! 5/23! HS 2013 Sexual selection • Male reproductive success generally limited by access to fertile females ! • Female reproductive success generally limited by access to resources and safety (+ quality of mate) => Sexual dimorphism: Smaller, less armed, less ornamented females! • Intrasexual competition: Intense among males, favors bigger weaponry, higher sperm production, mate guarding. Also leads to higher risk taking of males & higher death rate through diseases (different priorities)! • Mate selection: Usually by females. They favor traits that hint on good genes, direct benefits (& inbreeding avoidance, „sexy sons“). Limited in primates, as coercion by males is much higher (=> less choice for females)! • Sexual conflict: Different optima for males/females => sexual coercion (penetrating sexual organs, stronger males than females), Bruce effect (induced abortion) or Infanticide! • To limit infanticide: Create paternity dilution/illusions => males don‘t dare to kill offspring, as it could be their own => polyandrous mating, mating even if no chance for pregnancy exists and unpredictable ovulation! ! Preconditions for social complexity • Group living! • Stable groups & individual recognition! • Slow life history! • Diurnal activity period! ! Written by Joel Lüthi, artwork from ppts! 6/23! HS 2013 Derived features unique to humans Life history • Far longer lifespan, slower development (speed of development is dependent on brain size across primates, a bigger brain also means a longer life)! • Bigger babies born at shorter intervals: Human kids need help for far longer, but weaning (Entwöhnung von Muttermilch) is much faster.! • This can only work out for cooperative breeders. Faster weaning thanks to help from males, siblings and grandmothers.! • Midlife menopause: Around age 50, women stop reproducing to help care for the offspring of their daughters. The midlife menopause is adaptive to this „grandmothering“, not a maladaptive byproduct of the longer life span:! • men remain fertile until around 70 & there have always been old women! • high mortality was mainly because of high child mortality => if you survived as a child, you always had a fair chance of becoming a grandmother! • Having a grandmother around increases the fitness of their daughter, leading to shorter inter-birth intervals, more children, younger age of first reproduction etc.! • Allomaternal care: Woman care for children that are not their own. Especially grandmothers who bring a lot of help to the family! ! Socio-sexual behavior • Long-term male-female bonds (‘marriage’): Pair bonds are universal, but monogamy is not that often, some form of polygyny is more common (~ 80%). Polyandry is not common (=> small testis size)! • Big sexual dimorphism: Size of external genitalia and penis, presence of breasts and buttocks. Males bigger than females (=> polygyny)! • Female attractivity => some degree of male choice (pair bonds with male investment). Attractivity is an indicator for long-term fertility (versus indicators for proximity to ovulation that these features mean in other apes): 0.7 Waist/Hip ratio & a BMI of 20-30 indicate higher fertility! • Male-male competition. Jealousy for males is about sexual infidelity, for females more about emotional infidelity (= commitment)! • Both sexes are choosy, because they form long term relationships, strong male parental investments. Females are more often concerned about direct benefits („salary“), males more about beauty.! • Our impression of beauty reflects signs for high estrogen levels => fertility! • Sex in private! ! ! ! ! Written by Joel Lüthi, artwork from ppts! 7/23! HS 2013 Hypersociality • Within-group altruism, including food sharing, based on prosociality:! • Cooperation is extraordinarily high, often high risk with non-kin, hard to protect against free-riders.! • Dictator game: You get 50$, decide how much you give anonymously to someone else, no strings attached. => Players give around 20% => proactive prosociality! • People are very concerned about their reputation as a good person (males somewhat more than females). Generosity increases with group size! • People comply with social norms when they feel they‘re being watched! • Ultimatum game: You get 100$, you decide how to share it with the other person. If the other person agrees, you both get the money, otherwise you both get nothing. Offers under 20-30% are routinely rejected, mean offer is 30-40% => People are willing to sustain costs to punish stingy partners (Altruistic punishment)! • We are calculated opportunists in our support & good at detecting cheaters! • Mostly due to cooperative breeding!! • Between-group antagonism, pervasive male-male alliances! ! ! Culture and cultural evolution How could humas diverge so far so fast? Humans are a young species, genetically still very near to the other great apes, yet remarkably different from them in many ways. Furthermore, there’s immense intra-species variation without big genetic differences. Only (cumulative) culture can explain this.! Culture: A symbolically mediated, shared system of meaning! • Homo sapiens ca. 200k years old, culture as we know it about 100k years in Africa, suddenly 40k years ago in Europe. Shown through superior technology, art, religion & clothing and shoes (see co-evolution of lice).! • Humans ate their way through the mega-fauna! • Humans spread through the whole world: Great apes only live in tropical areas, yet humans are able to live everywhere. Too fast to be genetic adaption, it’s cultural bootstrapping, adapting really fast to new environments and telling the others how to do so => expertise and population adaption depends on population size & stability! ! • The «Green revolution»: Domestication of plants and animals. Driven by external pressure or by internal development of innovations? Always started with dogs, then other animals, finally plants (independently from at least 4 centers)! Written by Joel Lüthi, artwork from ppts! 8/23! HS 2013 • Civilizations: In areas of high productivity, where agriculture first developed. Why did states arise? Agriculture lead to increased population, but less dispersal options.! => Either restrict population growth, intensify agriculture or seize land from neighbours. ! «Force, and not enlightened self-interest, is the mechanism by which political evolution has led, step by step, from autonomous villages to the state»! • Early civilizations! • Densely populated settlements (/cities)! • Efficient agriculture! • Social stratification, higher levels of polygyny! • Specialization of labor! • Record keeping/writing, especially for taxes! Culture is our most successful adaptation!! It produced a population explosion, followed by migration out of Africa. It enabled the buildup of local adaptations, the domestication of plants and animals and a gigantic variation in social organizations. ! Culture in other animals! We look for «Innovations spread and maintained by social transmission», not stably developing traits linked to external (ecological) or internal (genetic) differences.! Do other animals have culture? ! Mechanisms of culture: Social learning! • Gregariousness: Follow the crowd => you’ll be in the same environment & therefore learn the same things! • Enhancement: Develop an interest for the things the others are using! • Observational learning: Contextual imitation or even production imitation (=> novel actions from learned components)! They need increased ability to copy actions precisely.! Great apes learn socially! Children watch their mothers. Shown in chimpanzees & orangutans, probably from a common ancestor.! ! But: Other great apes lack cumulative & normative culture!! Cultural evolution is faster and more efficient than organic evolution. Why does culture remain so simple in other animals? Written by Joel Lüthi, artwork from ppts! 9/23! HS 2013 The change needed to make cumulative culture possible is not in intelligence, but in social transmission. Very high social tolerance & active teaching is the onset of our cultural evolution!! Humans were just in the right spot for this to happen: Cooperative breeding produced hypersociality & active teaching! The stimulus for cumulative culture was probably more social than cognitive Variation in human culture Depends on innovation rate, efficiency of social learning and many population variables (size, social tolerance, exchange between groups).! Examples: ! • Humans in Tasmania cut off from all others => lost most of their culture! • Neandertalers: Weren’t less intelligent, but lived in smaller groups, lower density => less culture, less tools, less art! ! Some parts of explaining human culture is also gene-culture coevolution, e.g. selection on learning abilities or lactose tolerance, resistance to diseases. Written by Joel Lüthi, artwork from ppts! 10/23! HS 2013 Evolution of language and intelligence What is language «A systematic means of communicating ideas or feelings by use of conventional signs, sounds, gestures, or marks having understood meaning»! • Functional referentiality: Words mean something, refer to something! • Displacement: Refering to absent objects! • Conventionality: Connection is arbitrary! • Syntactical structure: Different combinations have different meanings! • Productivity: ability to produce endless number of sentences! • Negation: ability to state that something is not the case! ! Animal communication • Vervet monkey can warn for specific dangers => Functional referentiality! • Orangutans: Different population make different sounds => Conventionality! • Combination of calls can add meaning (when given contradictory signals, reaction is reduced) => Syntax! • Honey bees can give directions to things not present => displacement (but it’s not learned, it’s inborn)! • No animals known use productivity or negation. Also, extensive vocal learning & use of phonemes is quite uniquely human! • We can teach bonobos to understand language (Kanzi), but not to speak. We can train them to use symbols though => cognitive factors seem to be present, but dormant (but bonobos won’t use this communication with other bonobos) => no «Mitteilungsbedürfnis»! ! Evolutionary history • Speech is breathing control! Australopithecines weren’t able to speak, Neanderthalers were.! • FOXP2: Essential for language. Shared with Neanderthalers, ca. 400-500Kya => common ancestor!! • Precursor of language: ! • Gestures: Similar brain region, speech is gesture-supported, apes use it for intentional communication, but without syntactical structure & always imperative on present objects! ! • Vocal: Is semantic & syntactic, but great apes are born with knowing most sounds already, not much new invention! Language as an adaptation Innate predisposition to speech: ! Written by Joel Lüthi, artwork from ppts! 11/23! HS 2013 • Small children learn to speak by imitating adults! • Supported by anatomical adaptations (Kehlkopf tiefer => Risiko des sich Verschluckens)! ! What do we use language for?! Teaching, within-group altruism, collective action => sharing & donation of information, Mitteilungsbedürfnis! => all things human foragers needed!! Cooperative breeding provided the stimulus for the evolution of language! ! The Evolution of Brain & Intelligence • Marsh’s Rule: Relative to body size, brains are growing in evolution. Also valid for the evolution of primates and hominins! • Relative brain size predicts intelligence pretty good in primates! • Advantages of intelligence: Machiavellian Intelligence, mental maps, technical intelligence or general behavioral flexibility! • But why don’t all animals have such big brains? => costs! (constant, not reducible) => search for net benefit! ! Costs: Slower development, less (but fatter) children! Key determinant of brain size is not demand, but cost & opportunity to generate the required energy! Written by Joel Lüthi, artwork from ppts! 12/23! HS 2013 Krützen: Human evolutionary genetics What genetic changes have made us human? Macroscopic (FISH: 2Mb resolution):! • One chromosome fusion => a chromosome less than other great apes! • Chromosomal rearrangements: Chromosomes show some structural differences among primates, more with increasing phylogenetic distance! !Hybridisation of human & chimpanzee DNA:! • DNA shows 96-98% similarity, but the function of the differences is not shown with this method! !Sequencing (now for reasonable prices):! • Difficulties: only 1.5% coding DNA, 3% regulatory (mitochondrial DNA is much easier to compare, as most of its few genes are known & highly conserved)! • Shotgun sequencing: Works only for known species, when genome is already sequenced! • Genome comparison (single copy DNA): Comparison of aligned sequences => only 1.23% difference (30-60Mb). High divergence in Y chromosome, low divergence in X chromosome => Which of those are functional changes? Hardly any known. Exception: FOXP2: regulatory gene for development of language (only 2 SNIPs in humans compared to Chimps)! !Gene expression (Microarray analysis: mRNA to cDNA, cDNA hybridisation on chip)! • Rhesus, Chimp & Human: No significant differences expression in blood and liver, but significant differences in brain tissue! 1-2% sequence divergence, mostly in regulatory genes Levels of genetic diversity • Genetic diversity of great apes: Low population numbers, all species endangered, highly restricted distribution! • D-loop of mitochondrial DNA (fast evolving) is used as a marker! • The human species is genetically less variable than other species!! • Within & between subspecies, diversity in humans is low. But variation in humans within populations is bigger than between => contrary to other great apes! • mtDNA gives common ancestor of humans ca. 152-234kya! • Genetic diversity much higher among Africans compared to non‐ Africans! Written by Joel Lüthi, artwork from ppts! 13/23! HS 2013 • Orang-utans: Very strong separation between sampling sites because split took place ca. 3Mya (although radiation is rather recent)! • Denisova: New homo species found, just with mtDNA (basal of H. sapiens & neanderthaler)! !Reasons for small diversity in humans:! • Very recent speciation event! • Small ancestral population (~10k)! • Demographic events (bottlenecks)! • Stochastic events! => Out of Africa model with exponential growth, cradle of humankind in East Africa! ! Species, subspecies and races • Using a cluster-based algorithm, human ethnicities can be found from 377 microsatellite loci very well => 6 main genetic clusters! • BUT: Variation within clusters: 95%, between groups only 5%! • Most differences are because of phenotypic plasticity:! • average height rose a lot in last 200 years & differences between social classes visible! • Africans are slimmer & taller than inuits! • Distribution of skin colour is North-South => does not represent phylogenetic relations! Tree based on morphological similarities is quite different from phylogenetic tree (=> convergent evolution)! => Races present only cultural categories, differences are mostly local adaptations! ! Recent human evolution • Sickle cell anaemia: heterozygots have an evolutionary advantage against malaria, homozygosity is lethal => present in Africa, but not in Europe! • LACP => ability to digest milk after early childhood: Not present on the whole globe, different versions of it in different regions! • AMY1 copy number increased in populations with high-starch diets! => There is ongoing selection on protein coding genes, especially transcription factors, immune system, cytoskeletal protein & membran traffic proteins! Ongoing evolutionary plasticity (especially of the brain), but many selection pressures have been eased Written by Joel Lüthi, artwork from ppts! 14/23! HS 2013 Zollikofer: Comparing humans and chimps Two major «trends» in human evolution:! • terrestrial bipedal locomotion: X-Beine => Schwerpunkt besser für aufrechten Gang! • increase in brain size: Viel kleineres Gesicht, viel grösseres Hirnvolumen. Schädel vorne ziemlich platt. Beim Menschen wächst v.a. das Gehirn, beim Schimpansen v.a. das Gesicht! ! Schädel • EvoDevo, Reichert’s theory: Erster Kiemenbogen der Knochenfische (Teil Kiefergelenk) ist bei Säugetieren das Innenohr => Die Evolution erfindet wenig neu, sondern gestaltet bestehendes um (siehe auch Duplikation Hox-Gene). Funktionelle Einheiten müssen nicht gleichzeitig entstanden oder von gleicher Herkunft sein (siehe Schädel, Aufteilung funktionell und entwicklungsbiologisch unterschiedlich)! • Menschen haben überdurchschnittliches Gehirn für ihre Körpergrösse (aber keine Klasse für sich)! • Spezielles am menschlichen Gehirn: Grosses Grosshirn (bei Maus Kleinhirn/Grosshirn 50/50), prefrontal cortex (Assoziation, Planung, besonders gross beim Menschen).! • Sprachapparat: Kehlkopf nach unten gerutscht => Ermöglicht viel stärkere Vokalisierung. Aber Risiko des Verschluckens! Nicht gleichzeitig atmen und schlucken!! ! • Cranial Base: Viel geringere Nacken& Kaumuskulatur (weil Kopf auf Wirbelsäule ruht), äussere Schädelbasis stark gestaucht (rote Linie), innere ähnlich. Gesicht von oben gesehen sehr flach, unter dem Hirnschädel (statt vorne dran)! • Schimpansen haben viel grössere Eckzähne (Imponiermittel, Geschlechtsdimorphismus) => Lächeln eine Abwandlung davon?! ! ! ! Written by Joel Lüthi, artwork from ppts! 15/23! HS 2013 Zweibeinigkeit • Schwerpunkt genau in der Mitte (ausser bei älteren Menschen) => viel energieeffizienterer Gang! Gegeneinander verdrehte Bänder in der Hüfte verhindern wegkippen.! • Becken total verschieden: Beim Affen lang und versteift (kein wirkliches Becken), beim Menschen niedrig aber breit. Beckenschaufeln beim Menschen annähernd parallel zum Gang vs. vertikal beim Affen! • Abduktoren verhindern seitliches Abkippen beim Gang => Gerader, energieeffizienterer Lauf! • Gluteus Maximus beim Menschen nur am Po, beim Affen den ganzen Oberschenkel runter! • Evolutionäre X-Beine => Gewicht genau über Aussenseite des Kniegelenks => biomechanisch besser für aufrechten Gang! • Federstruktur der Wirbelsäule => Aufrecht stehen geht besser (=> double lordosis)! • Breiterer Brustkorb => Weniger Ansatzstellen für Armmuskulatur, dafür grössere Lungen! • Grosse Zehen nicht mehr gegenständig => Zur Unterstützung des aufrechten Ganges! ! Primate evolution General constraints Organismic (Intrinsic) constraints! • Body size: Knochen können eine gewisse Untergrenze nicht unterschreiten & noch stabil sein (=> Bräuchte Insekten-Bauplan) und gewisse Obergrenze nicht überschreiten (Statik => müssten im Wasser leben um grösser zu sein).! • Allometry (nicht lineares Wachstum): Durchmesser des Knochens ist proportional zu Länge3/2. Sieht man auch im Verhältnis der basal metabolic rate zum BMR ~ M2/3! Specific BMR ~ M-⅓ Gewicht. Specific BMR (BMR/M) ~ M ⅓.! - • Kleine Säugetiere brauchen mehr Energie pro Gramm Körpergewicht, brauchen also auch kalorienreiche Ernährung (Samen, Früchte, Insekten), während sich grosse Säugetiere auch von Blättern, Gräsern ernähren können (davon aber eine grosse absolute Menge brauchen)! • Allen’s rule: Endothermische Tiere haben tiefere Oberflächen/Volumen Verhältnisse in kalten als in warmen Gebieten (Inuit vs. Masai)! Written by Joel Lüthi, artwork from ppts! 16/23! HS 2013 • Bergman’s rule: Innerhalb einer Spezies nimmt Gewicht mit den Breitengraden und kälteren Klimata zu! • Allometry of locomotion: Kleine Affen können Bäume gleich gut rauf/runter wie horizontal, je schwerer ein Affe wird, umso weniger klettert er (Gorilla-Männchen klettert nicht). Aber auch: Je grösser, desto günstiger die horizontale Fortbewegung, Kosten ~ M ⅓.! - ! Environmental (extrinsic) constraints! • Zeit! • Geographie: Kontinentalverschiebungen! • Klima: Primaten leben nur in tropischen Zonen. Diese haben aber stark abgenommen!! ! Methods of reconstruction Dating! • Absolute: radiometric (C14: 100-50’000y, potassium-argon 40K -> 40Ar: 1-5 Mio years)! • Relative: ! • Palaeomagnetismus: Änderungen des Magnetfeldes anhand von Eisen im Sediment => Man kann bestimmte Zeiten ausschliessen! ! • Biostratigraphie: Zahnentwicklung (weil sehr schnelle Evolution bei Säugetieren)! Klimatische Rekonstruktion! • Pflanzenpollen: Sind enorm resistent, aber klimaabhängige Bildung => Klimarekonstruktion! • Sauerstoff-Isotope: Überschuss an schwerem Sauerstoff im Sediment bei kalten Zeiten ! • Strontium-Analyse => Herkunft von Menschen bestimmen (siehe Viking-raid)! • mitochondrial DNA: Molecular Clock. D-loop als hypervariable Region sehr wichtig! Written by Joel Lüthi, artwork from ppts! 17/23! HS 2013 Primate evolution II • Gradualismus vs. Punctuated Equilibrium! • Herkunft der Primaten in Asien?! ! Evolutionary «trends»! • Schädelmorphologie: ! • Postorbital bar bis zur vollständigen Augenhöhle. Gründe: Kleinere Gesichter => Kaumuskulatur nahe am Auge. Durch Augenhöhle wird Stabilisation auch bei Kaubewegung erreicht! • Grösseres Gehirn, Geruchsbereiche reduziert, Neocortex gewachsen! • Konvergenz & Frontation der Augen: Sichtfeld nur nach vorne, gerade (nicht nach oben)! • Mittelohr: Bulla petrosa, dickster Knochen unseres Körpers, um das Innenohr vor Geräuschen aus dem Schädel abzuschirmen! • Reduktion der Zähne: Zuerst Verlust der Prämolaren (schon bei Lemuren, ersetzt durch Eckzähne). Dann Reduktion der Prämolaren (auf nur noch 2 beim Menschen). Auch Komplexität der Zahnhöcker nimmt ab => Verbindung zu Ernährung: Insektivoren mit spitzigen Zähnen, Pflanzenfresser mit scharfen Prämolare & Fruchtfresser scharfe Schneidezähne! • Hands and feet: Beweglicher Daumen, Nägel & Fingerbeeren! ! => Adaptive significance?! In jeder Nische gibt es andere Säugetiere, die diese speziellen Anpassungen dafür nicht brauchen. Am ehesten wegen der Diversifikation der Ernährung (Insekten/Pflanzen/ Früchte), Koevolution mit Angiospermen! ! Fossil history Viele ausgestorbene Arten, manche tagaktiv, andere nachtaktiv (=> Grösse der Augen)! Lemuren: Moderne Formen nur in Madagaskar. Aber wie kamen sie dort hin?!! • «Rafting» from Africa (mit «Flossen»)! • Island hopping, vielleicht mit Tsunamis! • «Rafting» from India (then closer)! Ursprung der Primaten aus Asien oder Afrika.! Ursprung Neuwelt-Affen (S-Amerika): Aus N-Amerika während Global Warming (aber dort keine Spuren), «rafting» from Africa oder island hopping via Antarktis! Written by Joel Lüthi, artwork from ppts! 18/23! HS 2013 From ape to hominin Origin of Catarrhines (Old World monkeys & apes) • Radiation im Miocene («Epoche der Hominiden»), weite Ausbreitung, viele ausgestorben! • Zweibeinigkeit kein exklusives Merkmal der Menschenaffen, auch in ausgestorbenen Arten schon entwickelt! • Nur sehr wenige Fossilien von Menschenaffen! ! Hominids 1. Bipedal locomotion! 2. Short face (viscerocranium)! Evolutionary time 3. large brain (neurocranium)! ! Grade I:! • Partially arboreal! • Facultative biped! • Feminized canine (kurze Eckzähne)! • Woodland omnivore! • Sahelanthropus! ! Grade II: Australopithecines (4 - 1 Mya)! • Striding terrestrial biped! • Wide niche! • Pan-African! • Robust (=> Paranthropus: enormous face, big jaws) & gracile (=> Australopithecus)! ! Grade III: Homo (since 2.5 Mya)! • Enlarged brain! • Dentognathic reduction! • Technology reliant! • Old World range => global player! • Homo habilis, homo erectus! • Homo sapiens & homo neanderthalensis! ! Geology of fossil sites • East Africa: Rift valley; tectonic uplift & vulcanic ashes => Written by Joel Lüthi, artwork from ppts! 19/23! HS 2013 good fossil preservation, helps with dating! • West Africa: Sahel; once a huge lake => Sahelanthropus found there, still very ape like but bipedal! • South Africa: carstic caves; fossils landed in these caves by accident. Good preservation, but no signs for dating! ! Evolution of bipedalism • Adaption to new ecosystems? No, early hominids still lived in the forests! • Tool use? No, chimps & other apes use tools even though they’re not bipedal! • Widening of ecological niche: Maybe, large range is important. => Energy efficient locomotion! • Adaption to sun & wind => keeping temperature low. Meh…! • Free sight? Quadrapods manage to look around as well…! • Lacustrine predation: really that important?! ! Evolutionary trends in bipedalism • Dentition: Simpler teeth, smaller canines (Eckzähne), no room between canines & incesives => no grinding complex anymore! • Skull:! • Orientation of foramen (Hinterhauptsloch)! • Smaller jaws & teeth! • Steep face! • Feet & pelvis (Becken)?! • Brain size vs. body size: Rising strongly! • Paedomorphy: Adult hominid skulls has the proportion of juvenile ape! • Mosaic evolution: From Australopithecus to homo is not a straight line => compare with roubst Australopithecines! ! Early Homo • Larger than Australopithecus! • Relatively larger brain & smaller face! • Obligate terrestrial bipedalism! • Slow development! • Rapid dispersal «out of Africa»! ! How many species of homo existed?! It depends on the way species are defined. For hominids: Gradualism is better suited than punctuated equilibrium. Speak of demes (= local population of interbreeding organisms) better than different species! Written by Joel Lüthi, artwork from ppts! 20/23! HS 2013 Dmanisi sample site Quite a big variety in found skulls => probably just intraspecific variation, not many species (about the same amount of variation as seen in modern humans)! => All homo erectus, as a null hypothesis.! ! Homo erectus • From 1.8 - 0.5 mya! • Primitive (plesiomorphic) features:! • Endocranial volume: 550-1100ccm (brain/body not much increased)! • Neurocranium: tent shaped, low & broad for big jaws! • Shoulders & arms: more outward rotated than modern humans! • Derived (apomorphic) features:! • Vertebral column: S-shaped, like modern humans! ! • Pelvis: wider than modern humans! • Legs & feet: long femur, foot arch with non-opposable great toe => bipedalism! Tools • 5 modes of stone tools! • Stones tools represent only a small spectrum of actual tool use, but wood is not often preserved! • Tools follow «Out of Africa» model! ! Homo floresiensis: • ca. 1m tall, less than 100’000 ya, on an island in Indonesia, with big variety of tools! • Explanations for this «primitive» form of a hominid so recent:! • Pathology: Microcephaly. Not really convincing! • Descendent of Homo erectus: «Island dwarfing»; Small species get bigger (giant rats, Komodorans), large species get smaller (dwarf elephants). Reason: Ecology on an island, great animals wouldn’t find enough food.! Homo is just a normal species, as are all the others => also subjected to island dwarfing Written by Joel Lüthi, artwork from ppts! 21/23! HS 2013 Homo neanderthalensis & homo sapiens • Both H. neanderthalensis & H. sapiens have bigger brains (general trend to increased brain size, but always great variation)! • H. neanderthalensis has a bigger face, Oberaugenwülste! ! Homo heidelbergensis Late H. erectus? Early H. sapiens or early H. neanderthalensis? mtDNA shows it’s closer to H. sapiens, even though phenotypically, one would have assumed it to be closer to H. neanderthalensis.! ! H. sapiens • Out of Africa II ! • Africa: Herto, 150’000 ya! • Near East ca. 100kya, Japan & Europe ca. 30kya, N-America ca. 15kya! • First out of Africa was H. erectus. Maybe H. neanderthalensis as well! • In one wave or in many waves? Why have we found older fossils in Australia than in Asia?! • Much faster than expansion of H. erectus! • A multiregional modell seams unlikely (the same species formed in different places independently?)! • BUT: mtDNA shows, that newcomers (H. sapiens) mixed with indigenous population (e.g. H. neanderthalensis in Europe) => Parts of multiregional modell! Written by Joel Lüthi, artwork from ppts! 22/23! HS 2013 H. neanderthalensis • Allopatric speciation in Europe?! • Coexistence with H. sapiens for some time in Near east? Some fossils were found that look like hybrids? Probably not, probably just human with short legs! ! Skeletal features of H. neanderthalensis (vs. H. sapiens)! • Larger face, no chin, strong browbridge! • Larger thorax! • robust limb bones! • short tibiae! • Retromolarraum: Lücke hinter Weisheitszähnen! => adaption to arctic lifestyle, more athletic, clever hunters (big game?, close combat, in groups)? Unclear, could be just differences due to being its own species! ! Culture! • Dealing with dead: Burials & cannibalism (?)! • Cultural exchange with H. sapiens (tools: mode 3 => standardisation & more complex)?! • Genetic exchange: 1-4% of genomes of Eurasian people are from Neaderthals! ! Extinction! • Paleoclimate (glaciation with extreme climate fluctuations)! • Biological process: Too specialize, not adapted enough, assimilated by H. sapiens! • Historical process: random population fluctuations, «clash of cultures»! ! Evolution of H. neanderthalensis & H. sapiens Synapomorphies:! • Large brain (maybe just convergent evolution)! • paedomorphic => slow growth! • cultural variability? Doubtful! ! Autapomorphies:! • H. neanderthalensis: large, projecting face; long, wide, low neurocranium; short legs! • H. sapiens: prominent chin, small face, round braincase, extremly paedomorphic! ! Plesiomorphies:! • H. neanderthalensis: no chin, large jaws & teeth! • H. sapiens: dental morphology, body proportions! Written by Joel Lüthi, artwork from ppts! 23/23! HS 2013
