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Hominid Evolution: On The Origin of Humans
Questions to answer:
• How did we evolve into humans?
• What is the relationship between humans and other
primates?
• What is a hominid?
• What were early humans (hominids) like?
• How long have humans (hominids) been around?
• Where - and when - did modern humans
(Homo sapiens) originate?
• How have we changed?
• How did we come to populate the entire earth?
Evolution of Primates
• The evolution of primates is
characterized by:
– mobile limbs
– grasping hands (with opposable thumbs)
– a flattened face
– binocular vision
– a large, complex brain (for learned
behavior)
– a reduced reproductive rate
Mobile Limbs
• Most primates have flat nails as well as
sensitive pads on the undersides of
fingers and toes.
– Many also have both an opposable big toe
and thumb.
• Mobile limbs and clawless opposable
digits allow primates to freely grasp and
release tree limbs.
Primate Hands
Binocular Vision • Stereoscopic vision and resultant depth
perception allows primates to make
accurate judgments about distance and
position of adjoining tree limbs.
Evolution of Primates
• Prosimians were the first type of primate to
diverge from the ancestral primate line.
• Surviving anthropoids are classified into three
superfamilies.
– New World monkeys
– Old World monkeys
– Hominoids
What is a hominid?
• Any human-like
species, including us.
• Bipedal (walks on two legs).
• Intelligent (large brain, uses
tools).
Hominids are not the same as modern apes.
• Modern apes like chimpanzees,
gorillas, orangutans are not
bipedal.
• Modern apes do not have a large
brain case compared to ours.
• Modern apes do not make tools.
• However, chimpanzees are our
closest relative - our DNA is 98%
similar to theirs!
There have been at least a dozen different species of hominids
over the last five million years or so.
Since the first hominid fossils and artifacts were found, we
have found literally hundreds of others.
Anthropologists
compare the skulls,
teeth, bones, and
tools.
Together they begin
to show our family
tree - how we evolved
to who we are today.
Notice that most
species have gone
extinct - there are a lot
of “dead ends”.
Hominoid Evolution
• Proconsul is believed ancestral to hominids.
Hominids
• To be a hominid, a fossil must have an
anatomy suitable for standing erect and
walking on two feet.
– Bipedalism
• Human anatomy differs from that of an ape
largely because humans are bipedal while apes
are quadrupedal.
Australopithecines
• It is possible that one of the
australopithecines that evolved and
diversified in Africa 4 mya is a direct
ancestor of humans.
– Southern Africa
• Australopithecus africanus
– Eastern Africa
• Australopithecus afarensis (Lucy)
Australopithicenes
Australopithicenes
“Lucy In The Sky With Diamonds.”
• Discovered in Ethiopia in 1974.
• Dated at 3.2 million years old!
• 40% of her skeleton was found.
• Only four feet tall.
• Bipedal for certain. She walked upright.
• Her scientific name is Australopithecus afarensis, a distant ancestor to us, Homo sapiens.
An even more impressive fossil was found in
1978, but there were no bones to it at all.
Huh?
This discovery proved that there were
bipedal hominids even earlier than Lucy.
The Laetoli Footprints
• 3.6 million years old.
• Even older than Lucy.
• Clearly bipedal.
• Also showed that these early
hominids walked together.
So who were the “first” hominids? We still are not sure, but
we have found more fossil fragments as early as five million
years ago.
Human Evolution
Comparative Brain Sizes
Hand Shape
• Development of
more flexible
opposable thumb
• Allowed advanced
tool use
Pelvis shape
• Allowed early
hominids to
stand & walk
upright
• Gave advantage
of being able to
see around
them on the
savannah
Spine Shape
Changed
from "C"
shape to "S"
shape
Jaw Size •Jaw has reduced in size, reflecting changes in species diet
•Size of teeth have generally decreased, especially canines
Hominid changes over time
And when did our species - Homo sapiens - first evolve?
And how did we come to dominate the earth?
Classification Hierarchy
Kingdom Animal
Phylum Chordate
Class Mammal
Order Primates
Family Hominids
Genus Homo (“man”)
Species Sapiens (“wise”)
It is important to remember that there were several species in
the genus Homo that came before Homo sapiens.
• Homo habilis is the
earliest fossil
discovered so far.
(2.3 million years old)
• It means “handy man”.
• Homo habilis used very
simple tools.
Homo habilis
Homo habilis contd.
Homo erectus was a serious toolmaker and a fine hunter.
Evidence also indicates that they were the first to use fire.
Homo erectus
• ~ 1.5 Million years - ~ 80,000*
years . Homo erectus.
–Larger than H. habilis
–Larger brain
–Smaller face
–Was the first to use fire
–Allowed man to "break out" of Africa
into Europe & Asia
Homo erectus
Fossils of several other species in the genus Homo
have also been found.
• Homo ergaster.
• Homo heidelbergensis.
• The most famous is Homo
neanderthalensis
(Neanderthal Man).
• Neanderthal Man lived in
Europe.
• They too went extinct.
• Probably lived side-by-side with
Homo sapiens.
• Possibly interbred with them.
Homo neanderthalis
~130,000 - 30,000 years. Homo
neanderthalis "Neanderthal man"
– Probably not a direct ancestor - but
another offshoot from H. erectus
– Shorter, stockier, stronger than modern
man. Adapted to ice age.
– Larger brain size than modern man.
– Buried dead with flowers - first evidence of
religeous/symbolic thinking.
H. neanderthalis
And then there is…
Homo sapiens.
Anatomically modern humans.
• Oldest fossils found
so far are perhaps
195,000 years old.
• Found in Africa (also
in Ethiopia).
“Modern” man
• ~ 100,000 years to present - Homo
sapiens (modern man).
• Appears to have originated from H.
erectus in Africa, then migrated
outwards to Europe & Asia.
• Replaced existing species H. erectus &
H. neanderthalis
How to make a human: • Millions of years
ago, a majority of
northern Africa
was rainforest.
Ancestors to
man
Rapapithecus
and Proconsul,
were full arboreal
apes living in
these forests.
Changes • However,
approx. 5
mya the great
rift valley
formed in
east central
Africa.
Problems….. • The effect of this rift:
– isolated the ape population from the west
– created a “rainshadow desert”
Change of environment.
• change in precipitation
changed the landscape
from rainforest to
savannah
• apes developed new
form of transportation
since they could no
longer go through the
trees
• evolved the ability to
walk upright
Does that mean we all come from
Africa?
Yes! And recently, DNA analysis has proven this.
We are all Africans.
• DNA testing of thousands of
humans today, using a
simple saliva test kit, has
created a “map” of human
migration since modern
humans first left Africa
80,000 years ago.
We now have an excellent “road map” of how humans evolved
from Africa and migrated to populate the rest of the earth.
This evidence matches the fossils and fills in the gaps.
And if we follow the path of our
mitochondrial DNA back to the
beginning, somewhere in Africa…
We find that all humans alive today, including us, descended
from a SINGLE FEMALE.
Scientists have called her “Eve”.
From Lucy to “Eve”.
• Using fossils, artifacts, and
now even our DNA, we are
slowly getting a good picture
of our own hominid
evolution.
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