Anthro 101: Human Biological Evolution

Lecture 11: Early Genus Homo onto Homo erectus

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H. h

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Oldowan tools

H. e

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Modern bipedalityReduced sexual dimorphismAcheulean toolsBeginning of big game hunting1st to leave Africa1st Controlled use of fire

H. h

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H. n

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Modernized brainComplex toolsBig game hunters

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Stocky BodiesComplex behaviorInterbred with H. sapiens

Art, Language, RitualDiverse diet & toolsOnly surviving hominin

1.8 mya

2.5 mya

800

kya

300 kya

200 kya

Ancestor to the Homo lineage at 2.5 mya was:

• Bipedal, but still time in trees, small body size• Teeth adapted for generalized diet (NOT Paranthropus)• Sexually dimorphic, small brains• Living in mixed woodland, grassland habitats• 2.5 mya Africa further cooling & drying trend

• Appearance of the first stone tools!

JH Matternes, AMNH

Homo habilis & rudolfensis trend to bigger brainsand appear about 2.5 mya

• Brain size• habilis = 600 cc• Rudolfensis = 750 cc• Australopithecus & Paranthropus =

400 to 530 cc

• Skull more rounded• Less prognathic, smaller face• Smaller teeth, parabolic dental arcade,

thinner enamel

KNM-ER-1470 (H. rudolfensis)

KNM-ER-1813 (H. habilis)

KNM-ER-1470 (A. rudolfensis)

KNM-ER-1813 (A. habilis)

What kinds of selective pressures did hominins face 2.5 mya?

• Spending more time on on ground, less time in trees• More vulnerable to terrestrial predators

• Probably still slept in trees

• Might have formed large, multi-male groups

What kind of selective pressures did hominins face 2.5 mya

• Seasonal environment makes finding food harder• less plant food in the dry season• alternate food sources needed when dry

How did early hominins cope with seasonality?

• Australopithecines & Homo• smaller teeth may have eaten more meat• Carbon analysis of teeth supports this

• Paranthropus • huge molars, heavy jaws, and massive chewing muscles

• may have shifted to tough, dry plant materials• May also have eaten harder nuts & tubers• Possibly also ate meat

• Flexible diet in a fluctuating world

Hominin Transition: From meat to tools to culture

• Increasing reliance on meat characterizes the transition to genus Homo• May have led to changes in human behavior and social

structure• These changes begin to appear about 2.5 mya with the

appearance of stone tools

All of the early hominins probably made tools

• Chimps make and use tools • twigs to probe termite mounds• leaves to sponge up water• rocks to hammer open nuts• sticks as weapons

little trace in archaeological record

2.5 mya Hominins make stone tools: The Oldowan Toolkit

• Cores are round stones, with flakes knocked off to produce an edge

• used flakes as cutting tools• Remove skin• Butcher animals quickly

• Used cores as hammers & choppers

• knock off the flakes• Crack open bones for

marrow

Oldowan tools are simple, but took skill

• Piece together pile of flakes to the original core that they were struck from

• Toolmakers chipped as many as 30 flakes from 1 core• Various kinds of stone• No apparent design in mind when making

Next slide NSFW

Modern experiments suggest flakes were good for butchering game

Hominins also used tools for digging (insects, tubers)

• Wear patterns suggest use in digging up termite mounds

Experimental tool used to dig bulbs and tubers

Experimental tool used to dig into termite mounds

Fossil bone tool

Experimental tool used to dig tubers

Oldowan toolmakers got meat by scavenging & hunting?

• Most mammalian predators scavenge some of the time• No mammalian predators rely entirely on scavenging• Evidence suggests they did both

• See both small (scavenge) and large (hunted) bones with tool marks

• See tool marks made prior to carnivore tooth marks, and after carnivore tooth marks on same bone

In Olduvai Gorge we find butchery sites

• Large piles of tools and animal bones• some marked by tools, some by carnivore teeth, some both

• Hominins carried carcasses to butchery sites• Dismembered carcass there• Carry good bits away for more intensive processing• Scavengers waited for remains or competed for carcass

• Sites for raw stone material for tools• Made tools in these locations

Who made the first stone tools?(probably all of them!)

• A. garhi is possible candidate • Present at right time and place• Bones with stone tool marks found nearby

• But, many species present 2.5 mya• A. sediba (more recent)• Paranthropine species – precision grip• H. habilis & rudolfensis

• (habilis was the presumptive tool maker for long time)

Olduwan Toolmakers at the cusp of another adaptive shift

• Greater reliance on meat & tools• Changes in social life• Changes in brain• Changes in lifespan

• Hominin becoming more like us

Complex foraging a major part of later hominin evolution

• The genus Homo is marked by:• More hunted meat and extracted foods• More complex tools crucial for survival• Longer juvenile period

• learn foraging and tool skills• longer life span

• Greater paternal investment

increased pair bonding, reduced dimorphism• Origins of transmitted culture

• foraging techniques• possibly language

Definite Homo species

• Homo ergaster• Homo erectus• Homo floresiensis• Homo heidelbergensis• Homo neanderthalensis

• Denisovans• Homo sapiens

New Dmanisi skull may alter how we identify speciesduring this time period!

Transition to later Homo occurred between the Pliocene & the Pleistocene @ 1.8 mya

Upper

Lower Pleistocene Middle

1.8 mya .9 .3

Upper

Sharp cooling trend

Glaciers cover much of Europe

Major climaticfluctuations

The shift towards more modern Homo begins about 1.8 mya (not modern humans yet)

• Hominins in Africa with:• Skull similar to earlier hominins• Taller body • Long legs and short arms• Slower growth rate, longer

childhood• Reduced sexual dimorphism • Made Mode 2 tools

• Acheulean hand axes

H. ergaster KNM ER 3733

The shift towards more modern Homo begins about 1.8 mya (not modern humans yet)

• Similar finds in C. Africa, S. Africa, Asia• first hominin found in Asia

• Classified as Homo erectus or ergaster

• We will call them erectus, but• earlier forms in Africa

sometimes called ergaster • later forms in Asia sometimes

called erectusH. ergaster KNM ER 3733

Homo erectus combined ancestral and derived traits

• Ancestral features• receding forehead• no chin• narrowing behind eyes

• Post-orbital constriction

Dmanisi

KNM-ER 3733

Homo erectus combined ancestral and derived traits

Derived features• Occipital torus• Thick brow ridges• Thick skull • Smaller, less protruding face• Higher skull• Smaller teeth• Sagittal keel• Shovel-shaped incisors• Large orbits• Wide lower skull• Brain size ranged from 700 - 1200

cc

KNM-ER 3733

Some derived features of skull linked to diet(?)• All teeth smaller, especially molars

• tearing and biting with canines & incisors• Occipital torus & brow = thick ridges - buttress

• chewing and biting strength• NOT muscle attachments

• Sagittal keel?• Shovel-shaped incisors indicate heavy use of teeth

P. boisei H. erectus

Shovel-shaped incisors

Krapina Neandertal maxilla K, photograph © Milford Wolpoff

Post-cranial skeletons tell us a lot about H. erectus

• Nariokotome boy - East Africa• Most complete skeleton

• Tall adults (male 6’, female 5’)• Long limbs• Narrow hips

==> infants born with small brains, slow development

• Tooth age indicate faster maturing than modern humans, though

• Narrow shoulders• Thick bones ==> heavily muscled• Sexual dimorphism reduced, still > Hs Body proportions like modern humans in

tropics KNM-WT 1500

H. erectus mastered new subsistence skills• First (so far known) to leave Africa• More complicated stone tool kit - Acheulean tools• Controlled fire (possibly very early, definitely later) 1-2 mya• Relied more heavily on hunting - ate more meat

H. erectus 1st hominin to leave Africa in Lower Pleistocene

1.8 mya

1.7 mya

1.8 mya

Why now and not earlier?

Technologically more advanced

• 1.8 mya using Oldowan tools• 1.7 - 1.4 mya bifaces added to toolkit

• Bifaces = round cores shaped to make flatter with longer cutting edge all around• Hand axe & cleaver

• Acheulean = Bifaces = Mode 2• Acheulean + Oldowan = Early Stone Age

Hand ax

Cleaver

Hand axes reveal something about minds and habits

• All have same Height:Width:Thickness proportions • Unchanged for 1.5 million years

• common plan in heads of toolmakers• Used for specific purposes in standard ways• Knowledge passed along by teaching and imitation

Hand axes probably used to butcher carcasses

• well suited for cutting, dismembering animal carcass• Wear patterns support meat processing• Pointed end cuts through meat, rounded end fits in palm

• Flakes maybe also used for cutting• Biface holds sharp edge longer than flakes• Longer cutting edge than a flake