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UT AST 309L - The Origin of Intelligence

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1The Origin of IntelligenceThe Origin of Intelligencefi: Fraction of life-bearing planets whereIntelligence developsWhat is intelligence?Propose: “The ability to model the world,including the organism itself”fi Intelligence as continuumrelated to complexity of organismmilestone: human-level intelligence2Amoeba intelligenceacidamoebagood foodLaterThe Amoeba’s dilemmaInsert amoeba small hereA taco or a chalupa? I can't decide.3The smarter ParameciumInsert paramecium hereParameciumWallBonk!!I'll try this wayBut not THAT smart…Insert paramecium trap hereI'll try this way, etc., etc., ...Paramecium trap4 Information as Measure of IntelligenceEvolution of intelligence ~ increase in informationDNA: model of organism, the programA quantitative measure: # of bits of informationBit: Information in the answer to a yes/no questione.g. Purines PyrimidinesAdenine (A) Cytosine (C)Guanine (G) Thymine (T)Information ContentUnit # of Bits # of Pages # of Books1 base 21 codon 6Virus ~103 1Bacterium 1061000Amoeba 5 ¥ 108 500H. Sapiens* 6 ¥ 109 small library*~ 2% codes for proteinsfi 1.2 ¥ 108 bits5Evolution produced Increase in informationCaveat:much of DNA is “non-coding” fi hard to countInformation stored in DNA limited by fidelity ofreplicationSexual reproduction provides safety measurefor mutations in recessive genes# of Bits104106 - 107108 - 1010Error Rate10-310-610-9 - 10-8OrganismVirusBacteriumEukaryotes6Further Complications…• Humans make about 90,000 kinds of protein• Now it seems we have only 25,000 genes• What’s going on?• One gene can lead to different proteins– The mRNA is edited to remove introns– Sometimes exons are left out or introns in– Splicing controls gene expression– More common in more complex organismsBased on SaganDragons of Eden7Why Brains?To get more than 1010 bits (or 108?), needextra-genetic storageNeurons led to brainsHow is information stored in brains?Not entirely clearNeuron fires or not: 1 bit/neuron Yes or No Neurons are the building blocksNeuron has many inputs fromdendrites.Some favor firing, someinhibit firing.Based on balance, theneuron fires (or not).Electrical signal travels alongaxon (output).Releases neurotransmittersin synapse.They affect another neuron.Further complication: reverse signalling.Receiving neuron can release chemicals that inhibit the neurons thatsent “don’t fire” signals. Involved in learning.From slice of life project8Brains are DifferentNeuron firing controlled by many (~103) inputs -synapsesAn analog computer fi Hard to count~ 1011 neurons, 1014 synapsesCorresponds to 20 ¥ 106 books = NY public librarySurrogate Measure:Brain size or Brain mass/body massSmartDumb9Brain organizationBrain is reprogrammable , unlike genesfi Individual can learnTwo hemispheresMany functions parallel, but some specializedMany ways to divide brainLayered brain: reptilian brainlimbic system (mammals)cortexBrain size has increased (in some species) with timefi Evolution favors higher intelligence (sometimes)?A highly schematic representation of the reptilian complex, limbic systemand neocortex in the human brain, after MacLean.10Schematic views from the top and from the side of the rabbit, cat, and monkeybrains. The dark stippled area is the limbic system, seen most easily in the sideviews. The white furrowed regions represent the neocortex, visible most readily in the top views.Schematic diagrams comparing the brain of a fish, an amphibian, a reptile, a bird, and a mammal. The cerebellum and medulla oblongata are partsof the hindbrain.11The Big BrainHuman EvolutionPhylum: chordata - vertebrates - bilateral sym.Class: mammals arose in Triassic period ~ 225 Myr agoProliferated and “radiated” at end of cretaceous(~ 65 Myr ago) after extinction of dinosaursOrder: primates - late cretaceous ~ 80Myr ago12Primate CharacteristicsFew anatomical specializationsFlat fingernails, eyes in frontAdapted to life in treesPrimatesSuborders: prosimians anthropoids lorises tarsiers lemurs monkeys hominoids new world old worldThere are alternative schemesSuperfamily Hominoids (tailless apes)Gibbons Siamangs Gorilla Chimpanzee HominidsHylobatidae Pongidae13“Recent” fossil recordCenozoic Era (recent life)divided into Tertiary (3rd stage) andQuaternary (4th stage) PeriodsTertiary further divided into 5 epochsas follows: - dates (in million yrs. ago) arerough.EraPeriodEpochTimeEvents, Fossilsat beginningof Note(Myr ago)CenozoicRecent5000 yrsHistorical RecordsHomo sapiensHomo erectusQuaternaryPleistocene1.8–2.5Homo habilis4.2Australopithecus5.5ArdipithecusPliocene6–7SahelanthropusGapMiocene23–26RamapithecusDryopithecine ApesGapOligocene37–38AegyptopithecusEocene54TarsiersLemursTertiaryPaleocene65Tree Shrews - PrimatesProliferation of MammalsOrigin of Many OrdersMesozoicCretaceous14Early Primate EvolutionAdapting to life in treesClaws nails, grasp branchesindependent big toe, thumbNocturnal diurnalSmell vision stereo vision (eyes in front)Color visionMore complicated information processing, tooluse becomes possibleOrigin of AnthropoidsEocene transition to oligocene ~ 37 Myr agocooler, more grasslandsMore diurnal, some leave trees, lose tailFayum beds - Egypt 33 M yr agoEarly anthropoid fossil: aegyptopithecusUsed to be considered first hominoid, but nowsuspect monkey/ape split was later15Hominid EvolutionFossils now known back to ~ 6 MyrMolecular dating of chimp - hominid split 5-7 MyrMany variations now knownmany species co-existed in AfricaEarlier species show mosaic of human-ape traitsUpright walking preceded brain growth, tool makingMay not have arisen on SavannaLooks like “radiation”: many species arisingAll but one extinct now16Hominids in AfricaScientificAmericanJan. 200317Comparison of FemursFemur adapted tobipedality alreadyby 6 Myr agoVarious Family Trees18Consequences of New Fossils1. Even more clear that bipedal locomotionfar preceded big brains2. Bipedality not clearly connected to Savanna3. Several of the oldest hominids are veryclose to Ape - Human split4. Bipedality looks like key change thatseparated human and apeIdeas for Origin of Bipedality1. Tool use, big brain feedback2. Predator avoidance on


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UT AST 309L - The Origin of Intelligence

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