HOMINID EVOLUTIONHOMINID EVOLUTION

In aIn a nutshellnutshell

The Stage:The Stage:The Great Rift ValleyThe Great Rift Valley

K-K-ArAr Dating DatingDates new rock formationDates new rock formation

lavas, tufts, pumicelavas, tufts, pumicePotassium (K) - great abundance in earthPotassium (K) - great abundance in earth’’s crusts crust

K-39 93.2%K-39 93.2%K-41 6.8%K-41 6.8%K-40 0.0118% (radioactive)K-40 0.0118% (radioactive)

K-40 decays to Ca-40 (89%) and Ar-40 (11%)K-40 decays to Ca-40 (89%) and Ar-40 (11%)long half-life, 1.3 billion yearslong half-life, 1.3 billion years

Ar-40 Ar-40 –– inactive gas, diffusion during rock form. inactive gas, diffusion during rock form.Ratio of K-40 to Ar-40 denotes the moment ofRatio of K-40 to Ar-40 denotes the moment ofrock formationrock formation

Lines of EvidenceLines of EvidenceFossilsFossils DNADNA

DNADNA

Nuclear DNA

mtDNA

Y Chromosome

FossilsFossils

PongidsPongids and Hominids and Hominids

PongidaePongidae ( (pongidspongids))Modern Modern pongidspongids include: include:Gorillas (Gorillas (Gorilla gorillaGorilla gorilla))Common chimpanzee (Common chimpanzee (Pan troglodytes)Pan troglodytes)BonoboBonobo chimpanzee ( chimpanzee (Pan Pan paniscuspaniscus))Orangutan (Orangutan (PongoPongo pygmaeuspygmaeus))

HominidaeHominidae (hominids) (hominids)Modern hominids are representedModern hominids are representedby a single species:by a single species:Homo sapiens Homo sapiens sapienssapiens

PongidPongid/Hominid Split:/Hominid Split:The Fossil PerspectiveThe Fossil Perspective

There are no fossil remains of There are no fossil remains of pongidspongidsor hominids between 15-6mya.or hominids between 15-6mya.Paleontologists theorize that thePaleontologists theorize that thehominid lineage evolved from thehominid lineage evolved from thepongidpongid lineage 15-17 lineage 15-17 myamya. This. Thiswould provide hominids enough timewould provide hominids enough timeto evolve from the to evolve from the pongidspongids observed observedat 17 at 17 myamya::

RamapithecusRamapithecus, , SivapithcusSivapithcus, , GigantopithecusGigantopithecus, Proconsul, , Proconsul, DryopithecusDryopithecus

PongidPongid/Hominid Split:/Hominid Split:The Fossil PerspectiveThe Fossil Perspective

Possible Hominid Ancestors:Possible Hominid Ancestors:RamapithecusRamapithecusGigantopithecusGigantopithecusProconsulProconsulSivapithecusSivapithecusDryopithecusDryopithecus

Physical Characteristics:Physical Characteristics:large-bodied, typical primatelarge-bodied, typical primatecharacteristics, not wellcharacteristics, not wellunderstoodunderstood

PongidPongid/Hominid Split/Hominid SplitDNA PerspectiveDNA Perspective

Nuclear and Nuclear and mtDNAmtDNAevidence from modernevidence from modernhumans and humans and pongidspongidsindicates that they areindicates that they arevery similar geneticallyvery similar genetically–– chimps are 99% the chimps are 99% thesame as humanssame as humansTherefore, not muchTherefore, not muchtime is needed for thetime is needed for thehominids to evolvehominids to evolvefrom the from the pongidspongids ––estimate is 6-7 estimate is 6-7 myamya

First HominidsFirst Hominids

ArdipithecusArdipithecusMaeveMaeve Leakey LeakeyLake Lake TurkanaTurkana4-6 4-6 myamyaPongidPongid Physical PhysicalCharacteristics:Characteristics:

small brainedsmall brained

curved phalangescurved phalangesprognathicprognathiclarge canineslarge caninesdivergent toedivergent toe

BipedalBipedalpelvis, femur, footpelvis, femur, foot

AustralopithecinesAustralopithecines

Australopithecus Australopithecus afarensisafarensis; 3-4 ; 3-4 myamyacranial capacity 450-530cc,cranial capacity 450-530cc,““LucyLucy””, bipedal,, bipedal,primitive conditionprimitive conditionRobust lineageRobust lineageGracileGracile lineage lineage

Robust AustralopithecinesRobust AustralopithecinesAustralopithecus Australopithecus robustusrobustusA. A. boiseiboisei ( (ZinjanthropusZinjanthropus))A. A. aethiopicusaethiopicus(The Black Skull)(The Black Skull)1.8-3mya1.8-3mya

SagittalSagittal crest crestLarge brow ridgeLarge brow ridgeHuge cheeksHuge cheeksPrognathicPrognathicLarge molars/small Large molars/small incissorsincissors

(herbivorous)(herbivorous)Cranial capacity 500-700ccCranial capacity 500-700cc

GracileGracile Australopithecines AustralopithecinesAustralopithecus Australopithecus africanusafricanus1.5-3mya1.5-3mya

No No saggitalsaggital crest crestSmall, dish-shaped faceSmall, dish-shaped faceSmall molars/larger Small molars/larger incissorsincissors

(omnivorous)(omnivorous)Cranial Capacity 500-750 ccCranial Capacity 500-750 cc

Early Early HomoHomo Lineage LineageHomo Homo habilishabilisHomo Homo rudolfensisrudolfensisHomo Homo ergasterergaster1.8-1mya1.8-1myaEvolved fromEvolved fromAustralopithecus Australopithecus africanusafricanusWhat makes this speciesWhat makes this speciesHomoHomo and not and notAustralopithecusAustralopithecus??Cranial CapacityCranial Capacity750-850cc750-850ccTools: Tools: OldowanOldowan

Homo erectusHomo erectus

1.5-.3mya1.5-.3myaLarge brainedLarge brained(1000-1250 cc)(1000-1250 cc)Out of AfricaOut of AfricaFireFireTools: Tools: AcheulianAcheulian

Homo sapiensHomo sapiens

““ArchaicArchaic”” Homo sapiensHomo sapiens400,000-100,000 400,000-100,000 yaya

Modern Modern Homo sapiens Homo sapiens sapienssapiens150,000-present150,000-present

Neanderthals, 120,000-32,000yaNeanderthals, 120,000-32,000yaHomo Homo neanderthalensisneanderthalensis??

ORORHomo sapiens Homo sapiens neanderthalensisneanderthalensis

NeanderthalsNeanderthals

Europe andEurope andMiddle EastMiddle EastLarge bonedLarge bonedLarge faceLarge faceLarge brow ridgeLarge brow ridgeLarge molarsLarge molarsLarge nasal cavityLarge nasal cavityOccipital bunOccipital bunMousterian tool traditionMousterian tool tradition

Modern Modern Homo sapiensHomo sapiens

Diverse Paleolithic ToolDiverse Paleolithic ToolTraditionTraditionFossil EvidenceFossil Evidence

Different SpeciesDifferent SpeciesMultiregional HypothesisMultiregional Hypothesis

DNA EvidenceDNA EvidencemtDNAmtDNAY ChromosomeY Chromosome

Fossil EvidenceFossil EvidenceModern Modern Homo sapiensHomo sapiens

Separate Species: Separate Species: H. sapiensH. sapiens evolved from evolved fromH. erectus 400-500,000H. erectus 400-500,000yaya

MultiregionalMultiregionalHypothesisHypothesis

H. habilis H. erectusH. sapiens

H. sapiens neanderthalensis

Homo sapiens

DNA EvidenceDNA EvidenceModern Modern Homo sapiensHomo sapiens

mtDNAmtDNA, modern populations, modern populations120,000 years ago out of Africa120,000 years ago out of Africa

Y Chromosome, modern populationsY Chromosome, modern populationsTwo lines of migration out of Africa:Two lines of migration out of Africa:

50,000 and 40,000 BP50,000 and 40,000 BP

Neanderthals,Neanderthals,mtDNAmtDNA of fossils of fossilsNot in direct lineageNot in direct lineagewith humanswith humans

Hominid Evolution:Hominid Evolution:The Simplified VersionThe Simplified Version

Ardipithecus sp.

Pongidae Hominidae

Australopithecus afarensis

A. robustus

A. boisei

A. aethiopicus

A. africanus

Homo habilis

H. erectus

H. sapiens

H. neanderthalensis?

10-15mya

7mya

5mya

3mya

1mya

100,000 ya

Chimpanzees, Gorillas, Orangs