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‘. . . from so simple a beginning, endless
forms most beautiful and most wonderful
have been, and are being, evolved.’
Charles Darwin, from The Origin of Species
Leaves
The Origin of Species
In 1858, an Englishman
named Charles Darwin
rocked the science world
with an essay titled The Origin
of Species by Means of Natural
Selection.
His theory was that every
organism on Earth is a
descendant of those that
lived millions of years ago.
Species change and evolve,
and two different species may
be related, through many,
many generations, to an ancestral species (a common
ancestor). This was one of the great intellectual
revolutions of human history because until this time,
most scientists believed the Earth’s organisms were the
unchanging work of a creator, God, and that the Earth
was only a few thousand years old.
Darwin’s finches
Darwin spent most of his life developing his theory.
At the age of 22, he set sail on the HMAS Beagle, on a
five-year voyage that took him to the Brazilian jungles,
the Andes mountains and the Argentine grasslands.
Darwin’s travels opened his eyes to the vast range of
animal and plant species on Earth, and he began to
question the belief that the Earth and its species were
unchanging.
During his journey, Darwin visited the Galapagos
Islands, which are home to at least 13 species of
finch. He noticed that the different finch species
were similar in colour and size, but had variations in
their beaks that made them suited to the food sources
available on their particular island. Some used twigs
to extract insect larvae from tree branches, some
drank blood from seabirds, some removed ticks from
tortoises, and some ate seeds, leaves and flowers.
He proposed that all species were the descendants
of one shared, ancestral species, a ground-dwelling,
seed-eating finch, which had migrated out to all the
islands from the mainland. Over many generations
Insects
Tool-using
Darwin’s
finches
Grubs
Buds and fruit
Seeds
Darwin observed
that each species of
finch had a beak that
matched its method
of obtaining food.
the different groups of finches had evolved to suit
their different environments and feeding habits.
The groups of finches are now so different from one
another that they do not interbreed. Evolution is the
study of the change in inherited characteristics within
a group of organisms.
Darwin developed his theory while another
prominent English naturalist was reaching a similar
conclusion.
Alfred Wallace
Alfred Wallace’s writings
prompted Charles
Darwin to publish his
Origin of Species when he
did. Like Darwin, Wallace
travelled extensively
(in what is today known
as Indonesia) and
made many detailed
observations of the
variations between species.
Wallace wrote to Darwin in
1858 from the East Indies,
telling him that he had
a theory about evolution
188
Science Alive for VELS Level 6
Go to
worksheet 9.2
and natural selection. Darwin was shocked to realise
Wallace had reached the same conclusions as
himself. Darwin later described Wallace’s writings as
an almost perfect summary of his own life’s work.
Darwin was spurred on to submit both his paper
and Wallace’s to the Linnean Society science
conference held in London on 1 July 1859. Wallace
is recognised as a co-founder of the theory of
evolution by natural selection.
Lamarck’s giraffes
Jean Baptiste Lamarck (1744–1829) was
one of the first scientists to suggest that
evolution occurred, that is, that new species had
arisen and old ones had died
out. He proposed a different
means of change: he suggested
that changes acquired by an
individual during its lifetime
could be passed on to its
offspring. For example, giraffes
had become long necked
because they had stretched
towards leaves high up on trees,
and this stretching had been
passed on to their offspring. He
also believed that if an individual
did not use a particular feature, it would shrink
and gradually be lost over succeeding generations.
Although his theory of the inheritance of acquired
characteristics is now discredited, he made many
valid observations about diversity in living things.
Biogeography, the study of variation in living things
in relation to geographical regions, is the name
given to the studies that led Darwin and Wallace to
propose their evolutionary theories. They observed
in their travels that species living in the same area,
such as the Galapagos finches, were more similar to
each other than to species living in similar habitats
much further apart. If all species had been created
at the same time, why would this be so? To Darwin
and Wallace, this simple observation implied that
such species were related; that one had evolved
from another or they had both evolved from an
earlier, common ancestor.
6 A scientific theory is an explanation
REMEMBER
1 How old did many scientists
believe the Earth to be before
Darwin’s writings were
published?
2 What did Darwin observe about
the beaks of finches in the
Galapagos Islands?
3 In your own words, what is:
(a) common ancestry?
(b) evolution?
THINK
4 How was Darwin’s theory
different from Lamarck’s?
5 August Weismann (1834–1914)
did an experiment in which he
measured and cut off the tails of
mice and then bred the mice for
many generations. If Lamarck’s
theory of the inheritance of
acquired characteristics was
correct, what would you
expect to observe in the later
generations?
based on evidence that accounts
for observations made.
(a) What observations does the
Theory of Evolution account
for? One requirement of a
good scientific theory is that
scientists should be able to
make accurate predictions
based on the theory.
(b) Think of some predictions
based on the theory of
evolution.
INVESTIGATE
7 Alfred Wallace was one of the
founders of biogeographical
studies. He divided the Earth into
six major biogeographical zones,
each with its own characteristics.
• Nearctic: USA and Canada,
home to many reptiles and
other vertebrates
• Palaearctic: Europe and Asia,
features many deciduous forests
• Neotropical: South America, 16
of the 32 families of mammals
are restricted to this region
189
9. Evolution
• Ethiopian: Africa, a land of
tropical forest, savannah,
grasslands and desert
• Oriental: Indonesia, rich in
primate species like monkeys
and lemurs
• Australian: Australia, where
marsupials are dominant.
Use the internet to find out more
about these zones:
(a) What are the dominant types
of fauna and flora in each
zone?
(b) What are some of the unique
species in each zone?
(c) Include any other interesting
facts about the types of living
things in each zone.
Present your results as a poster.
�learning
Biogeography
I CAN:
describe the observations from
which Darwin and Wallace
developed the theory of evolution
explain the idea of evolution from
a common ancestor
explain the concept of
biogeography
describe the theories of Lamarck.
M^[h[Z_Zm[Yec[\hec5
W
hen Darwin published The Origin of Species in 1858, one sentence on the
last page caused a sensation. It read: ‘Much light will be thrown on the origin
of man and his history’. Darwin reached the conclusion that humans had evolved from the same family as the great apes. People found it very hard to believe our
ancestors were apes!
In 1871, Darwin published The
Descent of Man, describing the
relationship between men and
other species, including monkeys.
In 2005, scientists were able to
compare the sequence of complete
human DNA with the chimpanzee;
they found them 96% identical!
Other studies have shown close
relationships between the DNA of
humans and gorillas, orang-utans
and other primates. This genetic
evidence points to very close links
between humans and the great apes.
Monkey business
Human beings are mammals
of the Primate Order, which is
estimated to have evolved about
65 million years ago. Beginning as
small-brained, fruit-eating treedwellers, similar to the modern
day lemur, these creatures evolved
over millions of years into monkeylike animals. At some point in
time, probably between five and
15 million years ago, the humans
and apes of today began to evolve
separately.
There are many theories about
where, when and how modern
humans evolved.
The Hobbit
In 2004, scientists were
stunned by the discovery
of a fossil of a one-metre high
Homo floresiensis among the
remains of dwarf elephants, giant
rodents and Komodo dragons on
the Indonesian island of Flores.
Scientists believe it is a previously
unknown human species that
lived about 95 000 to 13 000
thousand years ago, at the same
time as modern humans — and
it’s very likely that they met!
From monkey to you!
At first Darwin’s
suggestion that
humans were
descended
from apes was
laughed at.
First hominid, Australopithecus
The Handyman, Homo habilis
DATED: 3–7 MYA FOUND: Africa
Australopithecus was the first group
classed as hominid (i.e. one of the
group of human-related species that
walked on two legs). It is believed
to be a common ancestor of both
humans and living apes. The first
remains of this
species were
found in northern
Ethiopia in 1974
and named
‘Lucy’.
DATED: 2.2–1.6 MYA
FOUND: South and east Africa
Homo habilis is known as the first
member of the genus Homo (of
which humans are the only living
species today). The ‘handyman’
used some of the earliest known
examples of stone tools, and had
a brain much larger than Lucy’s.
The Workman
Homo ergaster
DATED: 1.8–1.2 MYA
FOUND: Africa
Homo ergaster could
represent a different
population of Homo
erectus (meaning
‘upright man’). This
species migrated out of
Africa into Asia at least
1.8 million years ago.
200
Science Alive for VELS Level 6
Upright man, Homo erectus
DATED: 1.8 million–20 000 years ago
FOUND: Africa, Asia, possibly Europe
The most famous fossil remains
of Homo erectus were found in
the late 1800s: the Java man
(Indonesia), and Peking man
(China). H. erectus was very similar
to H. ergaster, but with a flatter
skull. H. erectus is believed to have
evolved in Asia then spread back to
Africa and possibly Europe.
Homo heidelbergensis
DATED: 900 000–100 000 years ago
FOUND: Europe
Homo heidelbergensis is considered
the first European hominid, and a
common ancestor of Neanderthals
and Homo sapiens. A famous
discovery in 1907, in Germany, was
the Mauer mandible (jawbone),
found with the remains of sabretoothed tigers, hippopotamuses and
rhinoceroses. Believed to be more
intelligent than Homo erectus, it used
advanced tools, including spears.
Go to
worksheet 9.5
Piecing it together
Palaeontologists have different
opinions about new fossil discoveries,
and whether they are on the direct
line of ancestry to humans. They look
at such features as brain size, skull
and jaw shape, and other features of
the skeleton. When considering the
variation between humans today, it
isn’t surprising there are disputes!
DNA studies provide powerful
evidence of relationships. A study
in 1987 supported the theory that
modern humans evolved in Africa
and migrated out from there. It is
believed humans reached the Near
East at least 90 000 years ago, Australia
by at least 60 000 years ago, Europe
around 40 000 years ago, and the
Americas by 12 000 years ago. Other
evidence conflicts with this ‘Out of
Africa’ hypothesis (see Mungo mania
below). Theories will remain tentative
and limited as long as new evidence
continues to emerge.
Mungo mania!
The discovery of ‘Mungo
Man’ in 1974 at Lake Mungo
in New South Wales cast doubt on
the ‘Out of Africa’ theory. DNA tests
show Mungo Man did not have a
direct African ancestor, suggesting
more than one Homo species or
subspecies contributed their genes to
modern Homo sapiens.
Neanderthal man, Homo
neanderthalensis
DATED: 230 000–29 000 years ago
FOUND: many locations in Europe,
western Asia
DNA evidence suggests the
Neanderthal was not an ancestor
of modern humans. Neanderthals
were short and stocky, and adapted
to the very cold climate of Earth at
that time. Their brains were larger
than modern humans, and it is likely
they used basic words, used spears,
sharp stone tools and clubs.
Early Homo sapiens
DATED: 100 000 years ago
Cro-Magnon man is believed
to be our direct descendant.
Cro-Magnons were tall, had
similar-sized brains to humans,
and they could probably speak.
They used complex stone and
bone tools, made jewellery from
shells and ivory, and produced
paintings on cave walls.
RESEARCH
9 Use internet research to
REMEMBER
1 How closely related is the DNA
of chimpanzees and humans?
2 When did the original
primates evolve and which
of today’s species were they
similar to?
3 What activities did
Cro-Magnon man undertake
that were similar to those of a
modern human?
4 What kinds of studies are
made of human fossil
finds, in order to determine
whether they come from
separate species?
THINK
5 Create a timeline showing
when the different Homo
species were alive on Earth.
Use this timeline to suggest
some alternative evolutionary
relationships between the
species.
6 Why are there different
theories of human
evolution? How are the
competing theories in science
often resolved? Why can’t
this approach be taken to
human evolution?
COMPARE
7 Obtain a study set of hominid
skulls or research them using
the internet. Make drawings
of each and take notes about
their differences. What
changes have occurred over
time?
IMAGINE
8 Imagine you are a
Cro-Magnon and your tribe
encounters a H. floresiensis
tribe. How do you attempt
to communicate? What kinds
of technology do you each
use? Can you live together
peacefully?
201
9. Evolution
complete a table comparing
the species below with
respect to:
• relative brain size
• height
• posture
• shape of skull
• teeth.
Australopithecus
Homo habilis
H. ergaster
H. erectus
H. heidelbergensis
H. neanderthalensis
H. sapiens
10 Investigate the controversy
surrounding the ‘Out of
Africa’ theory. Obtain
several copies of a world
map and mark on it the
possible movements of
the Homo species. Which
case do you think is most
convincing?
11 For a long time it was
believed Neanderthals were
not particularly intelligent.
Search the internet or library
and find out:
(a) why this was first
proposed
(b) why it might not have
been the case.
FIELD TRIP
12 Take a trip to the zoo and
observe the primates. Make
notes of the behaviour and
physical similarities to each
other, and to humans.
�learning
I CAN:
recall the scientific names of
the species of the genus Homo,
the early fossil evidence of the
evolution of the species
understand that evolutionary
theories will remain tentative
and limited as long as new
evidence continues to emerge
recall that DNA studies provide
powerful evidence for the
many evolutionary theories
that exist.