Year 10, General Science
3.4 Human Evolution
Fossils support the theory that humans evolved from a common beginning just like all the other
animals on Earth. Not everyone agrees with this theory. There is ongoing debate between
scientists and those who believe that humans have not evolved but were created by a god or gods.
Primates
Humans belong to the order Primates and have the same features as others in the primate group.
Primates have:

forward-facing eyes

five fingers or toes on each limb

four upper and four lower incisor teeth

opposable thumbs (for grasping things)

nails (not claws) on the fingers and toes

large brains for their body size

a flexible skeleton, with arms that rotate in
the shoulder socket to allow them to reach
behind their body.
Fossil evidence suggests that primates arose
from tree-dwelling, shrew-like insectivores
around 50 million years ago. This group soon
split into several divergent lines of evolution,
giving rise to the modern day primates. These
are the prosimians (pre-monkeys, similar to
lemurs), New World monkeys, Old World
monkeys and hominoids.
Evolution of humans
The most recently evolved group of primates is
called the hominoids. The hominoids include
the lesser apes (gibbons), great apes (gorillas,
chimpanzees and orang-utans) and humans.
The earliest humans almost certainly arose
from the same common ancestor as the other
hominoids. Although they have similar
ancestors, apes and humans are very distantly
related, taking different evolutionary pathways
millions of years ago.
Relatively few human fossils
have been
found, and the human
evolutionary process is
not definitely known. There is no accurate
record of when modern humans emerged, and
the exact relationships linking the few existing
fossil remains to today’s humans are
controversial.
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Year 10, General Science
Our distant relatives
The picture we have of the common
ancestor of modern apes and humans is
largely based on the fossils of
Dryopithecus, an ape-like animal, which
first appeared 25 million years ago.
Ramapithecus, another ape-like animal,
appeared 14 to 16 million years ago,
lasting another 6 million years. Some
believe Ramapithecus to be the ancestors
of the Asian orang-utan, while others see
a relationship to other apes and humans.
There are significant gaps in the fossil
records of 5 to 8 million years ago.
Southern ape
Although apes and humans had similar
ancestors in the past, the Homo line
diverged from the apes. The first true ‘human-like’ fossils
belong to the genus Australopithecus (meaning ‘southern
ape’, after the first fossils found in South Africa). The oldest
known fossils, Australopithecus afarensis (A. afarensis), are
around 4 to 5 million
years old. These bipedal
(walked on two legs) and
had a brain size
of
3
400 cm , less than onethird that of modern
humans (approximately
1450 cm3).
All
fossils
of
Australopithecus
have been found in
Africa.
More recent ancestors
The first clear representation of the Homo line is Homo
habilis (handy man). Fossils aged 1.5 to 2 million years
old found in East Africa reveal major changes
in
anatomy (a brain 50 per cent larger) and behaviour
(they used tools) from Australopithecus afarensis.
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Year 10, General Science
Homo erectus (upright man) came next. Although fossils have
been found in Europe, China and Africa, Homo erectus is often
called Java man, after the initial discovery site. The oldest are 1.5
million years old. Average brain size was 1000 cm3.
Other fossil humans
There are other species of the Homo line that have been identified.
Homo neanderthalensis (Neanderthal man) is thought to have lived
approximately 35000 to 100000 years ago. Neanderthals are thought
to have become extinct due to a change in climate or through
competition with other human species in Europe. The common
ancestor of humans and Neanderthals probably lived in Europe
around 600000 years ago.
Cro-Magnons lived about 10000 to 40000 years ago in
Europe and were nomadic hunter-gatherers. They were
anatomically similar to modern human, but more robust.
The exact reasons for their extinction are not known.
Anatomical changes
Whatever the exact pathways were
in the evolution from ape-like
ancestor to modern human or Homo
sapiens, some changes are clear:

the various forms walked more
upright than their ancestors

they developed smaller teeth,
reduced
eyebrow
ridges,
shorter arms, flatter feet and
non-opposable big toes

they developed flatter faces
and a progressively larger
brain size.
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Year 10, General Science
Cultural evolution
Humans have changed in many non-physical
ways.
We have learned how to use tools, and have developed
speech, forms of writing, artistic creativity, reasoning
powers and a sense of right and wrong. It is these
changes that most distinguish modern humans from
their ancestors. Humans have highly complex social
structures and an accumulation of learning and
knowledge. This stored experience is passed from
generation to generation, and affects our survival. This
is cultural evolution.
It is estimated that of all the animal species that have
ever existed, only 1 per cent are alive now. The ultimate
fate of most species appears to be extinction. Homo
habilis lasted for around 1 million years, Homo erectus
around 1.5 million. Modern humans have existed for
about 200000 years. With cultural evolution, humans
continue to acquire knowledge, enabling us to exert
more control over our environment than any other
species ever has, but we have probably done more
damage also. What does this mean for the future of
Homo sapiens?
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Year 10, General Science
Questions
Primates
Question 1.
List the characteristics of primates.
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Question 2.
What is the importance of a 50-million-year-old shrew-like insectivore to us?
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Question 3. Various features distinguish humans from the other primates. Give two examples
each of distinguishing features that are:
a physical
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b non-physical.
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Evolution of humans
Question 4.
Give five examples of hominoids.
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Question 5.
What distinguishes hominoids from the rest of the primates?
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Question 6. Identify three physical changes marking the evolution of humans from an ape-like
ancestor.
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Year 10, General Science
Cultural evolution
Question 7.
What is meant by ‘cultural evolution’?
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Question 8.
Give two examples of cultural evolution in action.
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_____
Question 9.
Place the following primates in correct order of evolution.
Old World monkeys
apes
humans
prosimians
New World monkeys
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Question 10. Place the skulls shown in the order of likely evolution. Explain your order.
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