Transcript Human evolution 1x

HUMAN EVOLUTION
Where we fit
Primate family tree
Hominoids
Primate features
Ape features
Ape vs. Human - skeletal
Ape vs. Human – skull
Ape vs. Human – brain
Ape vs. Human – other
Selection Pressures
Bipedalism
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WHAT WE’LL COVER
Biological evolution, Cultural evolution, Dispersal of hominins
Body changes,
genetic change
Learning,
language, tools,
clothing, fire,
agriculture
From Africa to the world:
When?
How long did it take?
Where do neanderthals
and “cavemen” fit?
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PRIMATE FAMILY TREE
Evolutionary speaking…
Apes branch off
here
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WHERE HUMANS FIT IN
To find our place it’s worth studying our taxonomic position…
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Fur wearin’, warm
blooded, young bearin’,
milk sucklers.
Order: Primates
Adapted to arboreal life
(living in the trees).
Family: Hominidae
Man-like. Let’s include our
ancestors and great apes.
Genus: Homo
Man
Species: sapiens
The thinking man!
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Hominoid = human-like (apes and humans)
HOMINOIDS
Hominid = humans, recent ancestors and great apes.
Hominin = only man’s ancestors
Recent DNA analysis has changed views of family/subfamily
classifications:
Chimps
Gorillas
Orangutans
Gibbons
siamangs
Old
Hominidae
classification
Pongidae/
Paninae
Pongidae/
Ponginae
Hylobatidae
Hominidae/
New
Homininae
classification
Hominidae/ Hominidae/
Homininae Ponginae
Humans
Hylobatidae
As our DNA is 98.6% the same as chimps, it has also been
suggested that chimps be placed in our Genus, Homo.
Manual pg 342(&3)
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APE FEATURES
Features of apes:
• No tail
• Rib cage is flattened
• Molars have 5 cusps (monkeys have 4)
• Locomotion is brachiating, knuckle-walking, or bipedalism.
• Posture partly (or fully) erect… leaving the hands free
The Y5 molar pattern
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SKELETAL DIFFERENCES
For walking:
• S –shaped spine
• Thumb fully opposable
• Pelvis is wide F
• Fingers are less curved
– for tool use rather than
brachiating
• Valgus angle; feet under COG
• Buttressed knee
• Big toe not opposable
• Foot arched
Manual pg 373/4
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SKULL DIFFERENCESManual pg 345/54
Foramen Magnum vertical – balanced
Nose width
Forehead
slope
Brow ridge
Protruding
muzzle
Canine
size
Sagittal crest (jaw
muscle attachment)
Nuchal crest (neck
muscle attachment)
Cranial capacity (as a
proportion of body size)
Molars
Zygomatic arch (jaw
(indicates diet) muscle passes through)
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BRAIN & SKULL DIFFERENCES
• Human have a large brain
(1400cm3 vs. ~ 450cm3)
Broca’s area
Wernicke’s area
• Well-developed cerebral cortex
(folded)
- memory
- speech (Broca’s area)
- understanding of language
(Wernicke’s area)
• Cerebellum (balance and
coordination) more developed –
bipedal locomotion and tool use
Cerebellum
Manual pg 375/6
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APES vs HUMANS
Other things
• More sweat glands
• Finer, and shorter, hair
• Larynx is lower and pharynx longer – for complex sounds
• Smaller teeth – ‘cos we used tools instead, as
well as having a more refined diet
• Rounded jaw – not rectangular
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SELECTION PRESSURES
Environment: In Africa around 6 m.y.a. forests were receding,
replaced by grassland. This reduced arboreal habitat driving
primates onto the ground.
Bipedalism: is more energy efficient than knuckle walking – these
species can travel further for scarce food. It allows tool use and
carrying of young. The body is also kept cooler (less surface area hit
by the sun and greater airflow around the body).
Height advantage: gained by being upright and being more able to
see food and predators.
Dentition: due to the nutty and vegetable diet canines reduced and
molars enlarged.
Hairlessness: reduces parasites, assists cooling.
Brain size: increases correlate to tool use 2.5 m.y.a. and more
recent developments are thought to be parallel to communication
improvements.
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The change to bipedalism is thought to have been explosive – within
2 million years or less. What could cause such a rapid evolution?
BIPEDALISM
Warmer, dryer climate
Infant held
more by
mothers arms
More time standing and
walking
Increased air
currents over body
Infant less
able to grasp
mother
More forwardly
directed big toe
More sweat glands
beneficial
Less body hair
beneficial
Infant less able to
grasp mother
Manual pg 372/377-8
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What are the adaptations for arboreal life that set primates apart?
PRIMATE FEATURES
• Dexterous hands – for clutching branches (maybe opposable
thumb) – see pictures on 347
• Sensitive fingertips with skin ridges with nails, not claws
• Eyes front – need to be good at judging distances
• Colour vision – recognise ripe fruit
Manual pg 344
• Poorer sense of smell, but emphasis on fine vision
• Single offspring and extended parental periods
- importance of learned behaviour
• Mobile hip and shoulder joints
• Unspecialised dentition – omnivorous diet
• Big bwain we got
• Strong social organisation