• Long gestation.• Reduced numbers of offspring/pregnancy.• Extended period of time to reach reproductive maturity• Greater dependence on flexible, learned behaviors

• Tendency to live in social groups.

• Menstrual and estrus cycles

Centers of gravity and pelvis shapeBipedalism

Chimpanzee: wrong pelvis for sustained bipedalism

In solidified volcanic ash – dated at 3.6 mya)

Australopithecus afarensis: Laetoli, Tanzania, Africa

Sounds and language

• Brain size

c. 55 mya Modern primates

Primate diversity

Madagascar

Prosimians

• Primitive• Southeast Asia, Africa, Indonesia, Madagascar• Snout with moist, fleshy nose-pad• Madagascan radiation: formerly 44 species of

lemurs. Size range.• Humans arrived c. 2,000 ybp• Therefore, many species exterminated

Specialized features

Aye-ayeMadagascar

LemursMadagascarLemurs: e.g., Ring-tailed--mostly terrestriale.g., Sifakas--arboreal

LorisesGabon, Central Africa

Different niches

TarsierSE Asia

ArborealSome with prehensile tails

New World monkeys

Almost exclusively arborealMost quadrupedal

Left: 7 speciesdifferent niches

Old World monkeys

Tails not prehensile

Most arboreal and quadrupedal

Colobus monkey

Exception: baboons: mainly terrestrial

What’s wrong?Humans share a commonancestor with great apes

Gibbons & SiamangsOn a evolutionary branchseparated from all otherprimatesRelatively small‘lesser’ apes 13-25 lbs.9 speciesSE Asia

A gibbon

Most have extremely longarmsPermanently curved fingersShort thumbs

OrangutanIndonesian Islands: Java & Borneo

On an evolutionary branchseparated from other great apesand humansPronounced sexual dimorphism males: 200+ lbs females: 100 lbs

Slow, cautious climbers“four-handed”Almost exclusively arborealLargely solitary

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Pronounced sexual dimorphism

Orangutan (juvenile)QuadrupedalBears weight on sides of hands andfeet

Gorillas

• Largest living primates• On an evolutionary branch separated from

humans, chimpanzees, and bonobos• Western and eastern equatorial Africa• Pronounced sexual dimorphism

– males: 400 lbs.– females: 150-200 lbs.

• Primarily terrestrial

2 Species:Western (Lowland gorillas) and Eastern (Mountain gorillas)

Young gorillaQuadrupedal

knuckle walking

Chimpanzees: most closely related to bonobos (same genus: Pan)Moderate sexual dimorphism: males: 100+ lbs; females: 80 lbsSome populations use tools; may engage in group hunting for meat

Chimpanzee

Bonobo

Not a “pygmy chimpanzee”Separate species

BonoboDemocratic Republic ofthe CongoHas attracted attentionbecause of a full repertoireof sexual activities used extensivelyin its social interactions

More linear body thanchimpanzeesLonger legs relative to armsRelatively smaller head

Brief bouts of bipedalism: mostly quadrupedal

• Threatened species• Bonobo future?• Rocky Mountain News: March 6, 2006• 1984: Est. 100,000• 2005: Est. 5,000• Why the drop in density?• Killed and sold (ca. $200/bonobo)• Prized as food.• Sold to local markets and urban restaurants