Transcript Multifactorial Traits

Human Evolution
www.okc.cc.ok.us/deanderson/index/human_evolution.ppt
The Evolution of Humans
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Theory of Evolution
• Science has overwhelming evidence that all life is
constantly evolving
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Natural Selection
• One mechanism of evolution
• Main concepts of natural selection
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Overproduction of offspring
Inherited variation in offspring
Competition
Best adapted in a given environment survive
and reproduce to increase their kind
• They are naturally selected
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Overproduction of Offspring
• Elephants (very slow reproductive rate)
– If all the offspring of one elephant pair survive and all
their offspring survive then:
• 750 years = 19,000,000 elephants
• 1200 years = Enough elephants to cover the earth!
• Beetles
– A handful that weighs 10 mg each
– 82 weeks
• 61,000,000,000,000,000,000,000 ton
– The weight of the earth!
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The Evolution of Humans
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Variation of Offspring
• Offspring of the same
parents are different
from each other
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Competition
• Since more individuals are born than can
survive for an extended period of time, they
compete for resources
– Food
– Living space
– Mates
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Best adapted to a given environment
are selected to survive
• Brown bears
– Adapted to survive in
Oklahoma
• Polar bears
– Adapted to survive in
Alaska
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The Evolution of Humans
The Ecological Theatre
 The Stage: East Africa
 The Setting: A time of unrest...
 Geologically…
 The rift zone - uplifts, rifting, volcanoes
 Climatically…
 A series of glaciations
 Global climate change
 Changes in sea level
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Sequence of Human Evolution
• Hundreds of fossils
have been found
• Some of the major
fossils will be
discussed in this
presentation
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Australopithicus afarensis
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3.5 million years ago
Nicknamed Lucy
Walked upright
Small brain
Skeleton human like
– Feet
– Pelvis
– Upright stance
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Comparative Anatomy
Lucy
Gorilla
Human
• Gorilla pelvis adapted for knuckle walking
• Human pelvis adapted for upright walking
• Lucy’s pelvis very similar to human pelvis
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Knuckle Walking
• Requires an elongated
pelvis and long arms
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Lucy’s pelvis allowed her to walk
like a human instead of an ape.
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Fossilized Footprints
• Footprints left when a
a pair of
Australopithecines
walked in the ash of a
recently erupted
volcano
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Skull Anatomy
Lucy
Chimp
• Thick brow ridges like a chimpanzee
• Cranial capacity 400 cc. Chimp 350 cc.
• Teeth similar to human teeth
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Lucy: A Transitional Fossil
• Transitional fossil shows
characteristics of two kinds
of animals
– Represent the transition from
one organism to another
• Ape characteristics
– Skull
– Cranial capacity
• Human characteristics
– Walked upright
– Feet
– Pelvis
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Australophithicus africanus
• 2.8 million years ago
• Cranial capacity 460 cc
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Homo habilis
• Cranial capacity 630 cc
• Flatter face than
Australopithecines
• Used tools
– Nicknamed handy man
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Homo erectus
• 1.8 million to 35,000
years ago
• 1,000 cc cranial capacity
• Large brow ridges
• Sloping forehead
• More advanced tools than
H. habilis
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Homo erectus
• Skeleton very similar
to modern man
• Used fire
• Traveled
– Fossils found in Africa,
Europe, China,
Indonesia
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Homo neanderthalensis
• 135,000 to 25,000 years
ago
• Cranial capacity up to
1750 cc
– Larger than modern man
• No chin
• Sloping forehead
• Buried dead with tools and
flowers
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The Evolution of Humans
The Cro-Magnons and the Neanderthals
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Homo sapiens
• 200,000 years ago to
present
– Photo is a skull
100,000 years old
• 1400 cc cranial
capacity
• Vertical forehead
• Pronounced chin
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The Evolution of Humans
• What about the
Neanderthals?
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The Evolution of Humans
• What about the Cro
Magnons?
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Modern Homo sapiens
• Small front teeth
• Small brow ridges
• Rounded cranium
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Sequence of Human Evolution
One of several possibilities
Homo
neanderthalensis
Australopithicus
afarensis
Australopithicus
africanus
Common
ancestor
Homo
habilis
Homo
erectus
Homo
sapiens
Modern
apes
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Evolution of Skull
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Cranial capacity increases for a larger brain
Face become flatter
Brow ridges become smaller
Forehead becomes higher
Chin develops
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Tools used to learn about our
evolutionary past
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Study of fossils
Comparing DNA
Comparing chromosomes
Comparing protein sequences
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Paleontology
• Study of fossils
– Allows us to see
anatomical similarities
between us and
organisms that lived in
the past
– Allows us to see how
our ancestors have
changed over time
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Comparing DNA
• Human DNA
compared to:
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Chimpanzee 99% same
Gorilla 97.7% same
Orangutan 96.3% same
Another human 99.9%
same
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The Evolution of Humans
The Great Leap Forward
• Due to evolution of a mechanism that allows
speech and language?
 Characterized by the appearance of...
• Use of symbols...
 Complex tools...
 Innovations in hunting techniques and strategies...
 Increased population size, development of social
systems...
 Houses, boats, long distance trade, ornaments
 Art, music, rituals...
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The Evolution of Humans
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