Human Evolution

Primate Characteristics

• Opposable Thumb and often toe, flat nails

• Binocular Vision with Forward Facing Eyes – brain simultaneously receives information from both eyes about an object, helps builds up a 3-D image of the object

  • Vision is the primary sense 

• Large Brain

• Loose shoulders and hips

• Longer life spans

• Highly social, frequently with very complex social behaviors and hierarchies 

Prosimians

• Group of “pre-monkey” mammals that consist of two groups (pro- before)

  • Strepsirrhini suborder (which includes galagos (bush babies), lemurs, loris, and more) 

  • Tarsiiformes infraorder (which is made up of tarsiers and is the lineage that gave rise to true monkeys).

• Most ancestral primates

• Characteristics 

  • Long Snout, wet nose, nocturnal, arboreal, smaller brain to body size

Strepsirrhini suborder

includes galagos (bush babies), lemurs, loris, and more)

1 of 2 groups in Prosimian

Tarsiiformes infraorder

made up of tarsiers and is the lineage that gave rise to true monkeys

1 of 2 groups in Prosimian

Suborder Haplorrhini

Monkeys and Apes (Simians)

• (technically includes the tarsiers)

  • Diverged from other primates 45 mya

  • Better eye site and dexterity than tarsiers and lemurs

  • More active in day 

  • Larger brain relative to body size

Monkeys

• General Characteristics: 

• Arms and legs are of equal length 

• Have a tail

• Two Groups

  • Old World Monkeys

    • Tail not prehensile 

    • Nostrils open downward

    • Ex: Baboons

  • New World Monkeys

    • Found in Central and South America 

    • Prehensile tail

    • Nostrils open to the side, and far apart

    • Ex: Squirrel monkeys 

Old World Monkeys

• Tail not prehensile 

• Nostrils open downward

• Ex: Baboons

New World Monkeys

• Found in Central and South America 

• Prehensile tail

• Nostrils open to the side, and far apart

• Ex: Squirrel monkeys 

Hominoids

Apes

• Found only in tropical regions 

• Lack a tail- distinguishing trait from monkeys

• Arms longer than legs – good for brachiating- form of locomotion by which the arms are used to swing through tree branches

• Larger brains than monkeys 

• Many have complex social groups

brachiating

- form of locomotion by which the arms are used to swing through tree branches

Gibbons (Lesser Apes)

• Smallest of all apes 

• Nine species

• All in SE Asia 

• All arboreal- tree dwellers

• Monogamous

  • Live in families of 2-7

• Most are critically endangered or endangered due to poaching and habitat loss (palm oil plantations)

Homonids

The Great Apes

Orangutan

Part of Homonids (The Great Apes)

• Only found in Sumatra and Borneo

• Mostly arboreal

  • Quadrupedal fist walkers 

• Semi-solitary, but can be very social 

• Divided into three species

  • Bornean orangutan (Pongo pygmaeus, with three subspecies) 

  • Sumatran orangutan (Pongo abelii)

  • Tapanuli orangutan (Pongo tapanuliensis)

• Critically endangered due to habitat loss (palm oil plantations)

Gorillia

Part of Homonids (The Great Apes)

• Largest of the apes – males up to 450 lbs 

• Found in Africa only

• Ground Dwellers

  • Quadrupedal knuckle walkers 

    • on their phalanges

• Live in families of up to 50 with a dominant silverback 

• 2 species (with several subspecies)

  • Western gorilla (Gorilla gorilla)

  • Eastern gorilla (Gorilla beringei)

• Most are critically endangered due to poaching and habitat loss

Chimpanze and Bonobos

• Found only in Africa

• Ground dwellers

  • Quadrupedal knuckle walkers 

• Live in family groups of 20-120 with a fission-fusion style social structure

  • Bonobos are led by dominant females

• Tool users

• ~ 99% of DNA in common with humans (chimps and bonobos have 48 chromosomes

• 2 species (with several subspecies)

  • Bonobo (Pan paniscus) 

  • Chimpanzee (Pan troglodytes) 

Humans

• Diverged from a common ancestor with chimpanzees 5-7 mya

• Found globally

• 1 species – Homo sapiens

  • Evolved in Africa, radiated out over time, replacing other Homo species ~100,000 years ago

  • Direct origins still fuzzy 

  • No nice phylogenetic tree 

  • Many species coexisted

  • Some lineages ended, some continued and interbred (Neanderthals and H. sapiens)

“Evidence”

• Early human fossils and archeological remains 

  • offer the most important clues 

  • include bones, tools and any other evidence (such as footprints, evidence of hearths, or butchery marks on animal bones, etc)

• Mitochondrial DNA and Non-Coding DNA 

• Africans have many more genetic variations in their genes than humans in other parts of the world – indicates older lineage

• Humans in other parts of the world have variations of African genetic mutations – indicating common descent

Major Changes

• Bipedalism

  • Walking on two legs, upright posture

  • Trait arose 4 mya (transitioning to bipedal ~6 mya) – present in australopithecines

  • Allowed long distance migrations/movement

  • Problematic – changed arrangement of pelvis – birth canal rotated

  • Foramen Magnum location

• Reduced Sexual Dimorphism

  • Equal size = monogamy

  • Dimorphism = polygamy (polygyny) – males have to be large in order to compete and monopolize females

• Long term pair bonds, long period of parental care

• Development of complex cultural 

• Speech