Bài giảng Sinh học - Linh trưởng

LINH TRƯỞNGLINH TRƯỞNGĐặc điểm chungBàn tay (chân) có thể cầm nắmNão lớn hơn động vật có vú khácHàm ngắnĐôi mắt hướng về phía trướcTầm nhìn của mắt rộng Móng tay móng chân bằng phẳngBiết chăm sóc con cái Tập tính xã hội phức tạpPRIMATES	Earliest primates were likely arborealGrasping hands and feet are adaptations for hanging on to tree branchesOpposable thumb and big toeHomo is the only extant primate lacking an opposable big toePRIMATES	Modern primates divided into two subgroupsProsimians“Premonkeys”AnthropoidsMonkeys and apes (including humans)PRIMATES	Prosimians“Premonkeys”e.g., Lemurs, lorises, pottos, tarsiers, etc.Probably resemble early arboreal primatesPRIMATESProsimian primates and anthropoid primates diverged at least 45 million years agoPRIMATES	AnthropoidsMonkeys and apes, including humansOldest anthropoid fossils 45 million years oldNew and old world monkeys diverged by 40 million years agoNewOldPRIMATES	All New World monkeys are arborealSome Old World monkeys are arboreal, and some are ground-dwellingMost of both groups are diurnal and socialPRIMATES	Four genera of apesHylobatesGibbonsPongoOrangutansGorillaGorillasPanChimpanzees and bonobosPRIMATES	Modern ApesEvolved from Old World monkeys25 – 30 million years agoConfined exclusively to tropical regions of the Old WorldPRIMATES	Modern ApesLarger than monkeysGibbons are an exceptionBrains proportionally larger than monkeysPRIMATES	Modern ApesLong arms, short legs, and no tailsAll are capable of brachiationOnly gibbons and orangutans are primarily arborealSocial organization is variableGorillas and chimpanzees are highly socialGibbonHUMAN ANCESTRYHumans and apes have shared ancestry for all but the last few million yearsPaleoanthropology focuses on this short period of timeThe study of human origins and evolutionHUMAN ANCESTRYWhen measuring against the history o the Earth, humans are very recent additionsPerhaps we are not quite as important as we might like to believeHUMAN ANCESTRY"Humans are not the end result of predictable evolutionary progress, but rather a fortuitous cosmic afterthought, a tiny little twig on the enormously arborescent bush of life, which if replanted from seed, would almost surely not grow this twig again." - Stephen Jay Gould HUMAN ANCESTRYTerminologyAnthropoidMonkeys, apes, and humansHominoidGreat apes and humansHominidHumans and their bipedal relativesDEAR DR. LAURADid we evolve from chimpanzees?No. Humans and chimpanzees evolved from a common ancestor, which was neither a chimpanzee nor a human.DEAR DR. LAURADid we evolve from monkeys or apes?We did not evolve from any present day monkey or ape. However, the common ancestor we share with chimpanzees would certainly be considered an ape, and common ancestors of both humans and monkeys would certainly be considered monkeys themselves.DEAR DR. LAURAIf we evolved from apes, then why are there still apes?This misconception is due to the tendency of people to think of evolution as a linear progression toward some goal, which is certainly not the case. Adaptive radiations give rise to multiple species stemming from a single species.DEAR DR. LAURAWas the production of humans the ultimate goal of primate evolution?This view is simply testament to the arrogance and self importance of humans. Lets get over it, people; we’re not quite that important. ‘Nuff said.30 – 35 M.Y.A.Early anthropoids were still tree dwellers20 M.Y.A.Indian plate collided with AsiaThrust up HimalayansClimate became drierForests (present Africa & Asia) shrunkIncreased savanna (grassland) with fewer treesSome anthropoids increasingly exploited this new habitatDecreased reliance on arboreal environment~15 M.Y.A.Last common ancestor of gibbons and humansAnd of gibbons and chimps, gibbons and gorillas, and gibbons and orangutans, for that matter~10 M.Y.A.Last common ancestor of orangutans and humansAnd of orangutans and chimps, as well as orangutans and gorillas, for that matter~8 M.Y.A.Last common ancestor of gorillas and humansAnd of gorillas and chimps, for that matter~5 - 7 M.Y.A.Last common ancestor of chimpanzees and humansCLOSEST RELATIVE?What is our closest living relative?What species is the chimpanzee’s closest living relative? the gorilla’s? the orangutan’s?HUMAN EVOLUTIONMajor features of human evolutionIncreased brain sizeAltered jaw shapeBipedal postureReduced sexual dimorphismExtended parental careHUMAN EVOLUTIONMajor features of human evolutionIncreased brain size400 – 450 cm3 6 million years agoSimilar to modern chimpanzee1300 cm3 todayHUMAN EVOLUTIONMajor features of human evolutionAltered jaw shapeHominoid ancestors had longer jaws“Prognathic jaws”Feature retained by chimpanzeesJaws shortened during human evolution Flatter face and pronounced chinHUMAN EVOLUTIONMajor features of human evolutionBipedal postureHominoid ancestors walked on four limbs when on the groundTrait retained by modern apesBipedal posture evolved > 4 million years ago“Hominids”Cause of this change?Various hypotheses, but still unclearSome of these hypotheses are beautiful examples of cultural bias affecting scientific thoughtHUMAN EVOLUTIONMajor features of human evolutionReduced sexual dimorphismDifference in secondary sexual characteristics reduced between males and femalese.g., Male: female size ratiosOrangutan	2Gorilla	2Chimpanzee	1.35Human	1.2HUMAN EVOLUTIONMajor features of human evolutionExtended parental careEnhanced parental care and an enlarged brain enhance learningAssociated with behavioral complexity of humansHUMAN EVOLUTIONWhat does the fossil record tell us about human evolution?Many hominid fossils have been foundAll but most recent are from eastern or southern AfricaThese fossils represent many different hominid speciesSome hominid species coexisted with othersLaetoli footprints, over 3.5 million years oldHUMAN EVOLUTIONOur hominid ancestry is branching, not linearMultiple species of hominids often coexistedMost died out, but we are still here for nowHUMAN EVOLUTIONBipedalism evolved 4 – 6 million years agoHomo and Australopithecus genera best studiedBipedalism predated increased brain sizeAUSTRALOPITHECUSThe first australopithecine was discovered by Raymond Dart in 1924 in a South African quarryIdentified as an early humanAustralopithecus africanus“Southern ape from Africa”Fully erect, with a brain much smaller than oursThe evolution of bipedalism predates the vastly increased brain size of humansAUSTRALOPITHECUSHow can one establish bipedalism from a skull?a femur?pelvic bones?AUSTRALOPITHECUSIn 1974, David Johanson discovered a 40% complete Australopithecus skeleton“Lucy”Afar region of Africa (Ethiopia)Australopithecus afarensisFrom “Afar”3.24 million year oldAge determined by radioactive datingSlightly older than A. africanusAUSTRALOPITHECUSIn 1974, David Johanson discovered a 40% complete Australopithecus skeleton“Lucy”Humanlike posture, small brainBipedalism established by skull and pelvic bonesHuman-like below the neckApe-like above the neckAUSTRALOPITHECUSAdditional A afarensis fossils have been foundMany in the 1990sLongevity of the species at least 1 million yearsLaetoli footprints, >3.5 m.y.a.AUSTRALOPITHECUSAustralopithecus anamensisUnambiguously humanLived >4 million years agoAUSTRALOPITHECUSOther putative hominids6 million years oldVery close to chimpanzee/hominid branchingAUSTRALOPITHECUSWhich australopithecines led to Homo?Which were evolutionary dead ends?AUSTRALOPITHECUSA afarensis underwent an adaptive radiation Robust australopithecinesPowerful jaws, large teethAdapted for grinding and chewing hard foodsEvolutionary dead end Gracile australopithecinesSimilar to A. afarensisLighter feeding equipmentAdapted for softer foodsAncestral to homoHOMOHomo habilis“Handy man”First discovered in 1964Louis Leakey, et al.Earliest fossils placed in the genus Homo2.5 – 1.6 m.y.a.HOMOHomo habilisClear signs of modern hominid skull characteristicsLess prognathic jawLarger brain600 – 70 cm3First known use of manufactured stone toolsHOMOHomo erectus1.8 – 0.5 million years agoSometimes split into Home ergaster (earlier)Homo erectus (later end)HOMOHomo erectusTaller than Homo habilisLarger brainAveraging 1,100 cm3Reduced sexual dimorphismMale:female size = 1.2Same ratio as todayMay offer insight into social structureHOMO“Turkana boy”1.6 million years oldLarger brainLikely over 900 cm3 by adulthoodClassified as Homo ergaster or Homo erectusHOMOHomo erectusFirst hominid species to migrate out of AfricaColonized Asia by 1.5 m.y.a.Spread into Europe (timing less certain)HOMOHomo sapiensEvolved from H erectus or H ergasterIn Africa alone or multiregionally?HOMOHomo sapiensMitochondrial DNA (mtDNA) can be used as a molecular clockHuman genetic divergence ~100,000 years agoSupported my nuclear genetic markersesp., Y chromosome“Out of Africa”HOMONeanderthals“First” discovered in Germany’s Neander Valley1856 (1829 elsewhere)Lived 200,000 – 40,000 years agoBrains as large as oursShaped differentlyProminent brow ridgeSloping foreheadOccipital bunHOMONeanderthalsSpecies or subspecies?Homo sapiens neanderthalensisHomo neanderthalensisHOMONeanderthalsContemporary to more modern Homo sapiens“Cro-Magnon man”Ultimately disappearedWhy?HOMONeanderthalsmtDNA analysis of Neanderthal DNAExtracted from boneVery different from modern H sapiensIt is very unlikely that Nenderthals contributed significantly to our gene poolHOMOSure, maybe we are smart, but ..Diverse prokaryotes are ubiquitousArthropods outnumber all known species combinedThere are more species of bony fishes alive today than all other vertebrates combinedDinosaurs ruled the earth for much, much, much longer than we didWe are not as successful as many other groups