cranial morphology of homo erectus - knox college lecture.pdfhomo erectus/ergaster leakey team, 1974...

Cranial Morphology of Cranial Morphology of Homo erectusHomo erectusAlveolar prognathismLarger teeth than modernsSupraorbital torusLow foreheadPostorbital constrictionOccipital bunThick cranial bonesNo chinCranial capacity: 800-1100 cc (gradual increase)

The career of The career of Homo erectusHomo erectusAfrica 1.9 myaChina and Java 1.6 myaEurope after 1 myaJava, 35,000 years?Acheulean tools after 1.5 mya, fire after 1.3 mya

Meat + high-end plant foods

Mainly vegetarian diet, little processing

Brain size much larger than apes

Brain size close to apes

Stone toolsFew if any stone tools

Genus HomoGenus Australopithecus

If I Only Had a Brain . . .If I Only Had a Brain . . .

What does it take?

Staying coolStaying cool

PROBLEM:Most mammals cannot remain active in tropical daytime Brain cooling presents extra challenge

SOLUTIONS:Global cooling at time of Homo emergenceTriple benefit of bipedal postureSweat on hairless body 250 times more effectiveAltered arrangement of blood vessels cooling brain

Energy needs of Energy needs of an expanding brainan expanding brain

20% energy for 2% of body massGut vs. brain– Both expensive– Mutually exclusive

Reducing gut size– Depends on diet

Meat?

Meat and the BrainMeat and the Brain

Homo brain grows at fetal rate after birthEnergetics of nursing– Baby higher on food

chain – 10:1 efficiency drop

Maternal nutritionSignificance of meat

HighHigh--Payoff Plant FoodsPayoff Plant Foods

Roots– Abundant– Digging sticks – Nutritious if cooked

Nuts, etc.Skills, processing

(Did (Did gracile gracile AustralopithecusAustralopithecusever eat meat?�)ever eat meat?�)

Stable isotope analysis of South Africanafricanus fossils indicate C4 plants– Meat from grazing animals?

A. garhi from Ethiopia: tools and cut bones

KNM-ER 1808Homo erectus/ergaster

Leakey team, 1974East Lake Turkana, KenyaAge: 1.7 million years

Partial female skeleton displays pathological bone buildup, suggesting hypervitaminosisfrom eating carnivore liver. She must have been cared for during her long terminal illness.

Normalerectus

1808tibia

Hunters or Hunters or Scavengers?Scavengers?

Many species do bothWhat kind of scavenging?– Marginal scrounging?– Power scavenging?

Hunters or Scavengers?Hunters or Scavengers?Many species do bothWhat kind of scavenging?– Marginal scrounging?– Power scavenging?– Blumenschine’s non-

confrontational scavengingLouis Leakey– Experiments in low-tech

hunting– Traps and snares

“Mighty hunters” or opportunists?– rudolphensis and early

erectus likely opportunists– Later erectus a “mighty”

hunter?

Torralba Torralba andand AmbronaAmbrona

Late Homo erectus400,000 years ago

Males relatively less competitive

Males competitive

Males related; stay in group

Males in group unrelated; leave group at time of sexual maturity

Sex dimorphism 10-20%Sex dimorphism 100%

Genus HomoGenus Australopithecus

Humanlike body shape and fully dedicated bipedalism

Bipedalism + arboreal capability; intermediate body shape

Humerofemural index 70-75%

Humerofemural index 85-95%

Genus HomoGenus Australopithecus

Size, proportions and dimorphismSize, proportions and dimorphism

Kamoya Kimeu, Leakey team, 1984West Lake Turkana, KenyaAge: 1.6 million yearsCranial capacity: 880 cc

The Turkana boy is the most complete of any early skeleton, and it has enabled scientists to learn much about Homo erectus/ergaster. It died in early adolescence but would have reached a height of more than 6’ at maturity, with a cranial capacity of 909 cc.

KNM-WT 15000Nariokotome or “Turkana boy”

Homo erectus/ergaster

Turkana Turkana BoyBoy vsvs. Lucy. Lucy

Rib cage?Body shape?Pelvic shape?Waist (gut)?Tibia & ulna?

The Great LifeThe Great Life--History ShiftHistory ShiftLife History: Gestation, birth, weaning, developmental patterns, sexual career, life span, etc.Leakey: major shift in HomoEvidence: Dental growth rates, pelvic and skull measurementsAustralopithecus had short, chimplike childhoodHomo pattern:– Slow body growth, fast brain growth– Adolescent growth spurt

Brain growth from birth to adulthood:Ape 2xAustralopithecus 2.6xHomo erectus 3.3xHomo sapiens 3.5x

“Human grade” life history: long childhood, adolescent growth spurt, prolonged life span

“Ape grade” life history (age of weaning, sexual maturity, life span, etc.)

Humanlike dental growth pattern

Apelike dental growth pattern

Tripling of brain size from birth to adulthood

Doubling of brain size from birth to adulthood

Gestation period less than half that predicted by general primate pattern

Gestation period correlates with brain size as in other primates

Genus HomoGenus Australopithecus

Diet, Niche, & Life History

A Theory of Human Life History Evolution: Diet, Intelligence, and Longevity

Hillard Kaplan, Kim Hill, Jane Lancaster, A. Magdalena Hurtado, University of New Mexico

Evolutionary Anthropology, 9:4 (2000) pp. 156-184

• Relies heavily on hunter-gatherer studies

• Inter-species comparisons• Life history theory• Human capital theory

• Compatible with Lovejoy, Leakey• More remains to be done: Vague on

evolutionary timing, species• Much can be added in terms of culture

and language

The Theory

• Begins with ecological premises--the human adaptive niche (presumably from early Homo times if not before)

Human Niche

• “Humans are specialists in that they consume only the highest-quality plant and animal resources in their local ecology and rely on creative, skill-intensive techniques to exploit them.”

• Allows them “to colonize all of earth’s terrestrial and coastal ecosystems.”

Dietary Niches

Food Types• Collected

– Leaves, fruits, insects• Extracted

– Nuts, termites, tubers• Hunted

– Small game, birds, etc– Large game

• [Major scavenging?]

Learning and productivity

Life History Trends• Investment in skills• Long childhood

– Slow body growth– Rapid brain growth

• Adolescent growth spurt• Extended life span

– 2x chimpanzee – Post-reproductive women– Contribution to food supply– Labor and skills– Cultural “capital”

Lower Mortality:Part of Extended Life Span

• Group size• Food package size• Food sharing• Hunting skills and tools• Knowledge of animal behavior

Food exchange

• Male to female• Three generational flow, old to young• Support of reproduction• [Pair bonding and CSR?]

Flow Chart

Brain, intelligence, language

• Selective pressure for…• Conditions for…• [Role of home base?]

Language: gestures, mimesis, invented lexicon (eventually, syntax)

Apelike call systems

Increasing basicranial flexionApelike vocal tract; flat basicranium

Increasingly abstract thought (narrative binding)

Apelike intelligence

Food sharing, economic exchange, provisioning

Hand-to-mouth food consumption

Continuous sexual receptivity and pair-bonding

Estrus, visual and olfactory sexual cues

Home baseLack of home base

Genus HomoGenus Australopithecus

Example: Example: FLKFLK--Zinj Zinj ““living floorliving floor””Olduvai Gorge, Mary LeakeyZinj skull found thereThousands of mammals bones– Open-country species– Cut marks & tooth marks

Homo tibiaOnce near a lakeOldowan toolsManuports

Theories of Site FormationTheories of Site FormationHome base?Animal activity?Water action?Routed foraging?Picnic site?Tool cache?Kill site?Scavenged carcass?Palimpsest?

Home base, anyone?Home base, anyone?

Glynn Isaac vs. Lew BinfordSite 50, 1.5 mya?Terra Amata, France 400 kya

Altering environmentExtending daily activitySocial focus

SafetyWarmthHunting & technology

Promethean FirePromethean Fire

Language: gestures, mimesis, invented lexicon (eventually, syntax)

Apelike call systems

Increasing basicranial flexionApelike vocal tract; flat basicranium

Increasingly abstract thought (narrative binding)

Apelike intelligence

Food sharing, economic exchange, provisioning

Hand-to-mouth food consumption

Continuous sexual receptivity and pair-bonding

Estrus, visual and olfactory sexual cues

Home baseLack of home base

Genus HomoGenus Australopithecus

Who talked?Who talked?Contours of skull, neckReconstructed Australopithecusvocal tract is apelike– Could not make human speech sounds– High larynx

Human larynx is low– Flexed basicranium

erectus was transitionalTurkana boy’s vertebra had small spinal foramen– Limited ability to control muscles for

speech

proto-language?(more later . . .)

Fire and speechFire and speech

Larynx descends in Homo, for speechSusceptibility to chokingMeat is a common culpritMeat is important for brain growthCooked meat easier to swallow

Viva Prometheus!

Transitional Homo: Transitional Homo: The Late The Late ErectinesErectines

The Awkward Age . . .The Awkward Age . . .At 1At 1 myamya, erectus, erectusAt 100At 100 kyakya, modern sapiens, modern sapiensThe The inin--betweenersbetweeners::–– Cranial/facial morphology resembles Cranial/facial morphology resembles

erectuserectus–– Growing cranial capacity: 1100Growing cranial capacity: 1100--1300 cc1300 ccWhat to call them?What to call them?

Proposed namesProposed names

EACH HAS ITS PROBLEMS . . .EACH HAS ITS PROBLEMS . . .““Late Late Homo erectusHomo erectus””““Archaic Archaic Homo sapiensHomo sapiens””““HomoHomo heidelbergensisheidelbergensis””–– Diverse within, and fuzzy at the edgesDiverse within, and fuzzy at the edges–– Adds another name to rememberAdds another name to remember–– But gaining favorBut gaining favor

HomoHomo heidelbergensisheidelbergensis

A A HomoHomo heidelbergensisheidelbergensis SamplerSampler

SteinheimSteinheim, Germany, Germany250250 kyakya 1200 cc1200 cc PetralonaPetralona, Greece, Greece

300300--400400 kyakya 1220 cc1220 cc

BodoBodo, Ethiopia, Ethiopia600600 kyakya

KabweKabwe (Broken Hill), (Broken Hill), ZambiaZambia

300300 kyakya 1300 cc1300 cc

AtapuercaAtapuerca, Spain, Spain300300 kyakya 1125 cc1125 cc

AragoArago, France, France400400 kyakya 1166 cc1166 cc

MauerMauer, Germany (Type Specimen), Germany (Type Specimen)400400 kyakya

BoxgroveBoxgrove, England, England500 500 kyakyaHomo Homo heidelbergensisheidelbergensis??Rugged tibia,Rugged tibia, AcheuleanAcheulean tools, tools, evidence of big game huntingevidence of big game huntingSimilar 4Similar 4--500500 kyky old Europeanold Europeanacheuleanacheulean sites :sites :–– TorralbaTorralba--AmbronaAmbrona–– TerraTerra AmataAmata–– St.St. AcheulAcheul (Knox(Knox handaxeshandaxes))

The Family Blob

Homo erectus

H. heidelbergensis

H. sapiensNeanderthals

SpeciationSpeciationSpeciation