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Number 201
Humans: evolution or creation ?
In some parts of the US, the teaching of evolution, particularly human evolution, is considered blasphemous. Many people cannot accept
that humans have evolved from other species. This Factsheet reviews the controversy as well as recent exam questions on human
evolution.
The evidence for evolution includes:
Common biochemistry
Humans and other primates such as chimpanzees, gorillas and orangutans also have many distinctive physical and social similarities.
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Paleontology
all life has DNA or RNA as its genetic material
all life has the same 20 amino acids
Acanthostega lived 365 million years ago. Fig 1 shows an
Acanthostega fossil. Like other invertebrates it has a backbone
and limbs. But it has 8 fingers and 7 toes, unlike anything existing
now.
Haemoglobin in mammals is made up of four polypeptide chains,
two identical alpha chains and two identical beta chains. The
sequence of amino acids in these chains has been determined for a
number of different mammals.
Fig 2. Acanthostega fossil
Table I below shows a sequence of fifteen amino acids in an alpha
chain from four different primates: a chimpanzee, a human, a gorilla
and an orang-utan.
Table 1
eight fingers
Primate
Amino acid sequence in alpha chain
Human
KAAWGKVGAHAGEYG
Gorilla
KAAWGKVGAHAGDYG
Chimpanzee
KAAWGKVGAHAGEYG
Orang-utan
KTAWGKVGAHAGDYG
A= alanine
G = glycine
T = threonine
Y = tyrosine
D = asparragine
H = histidine
V = valine
seven toes
E = glutamic acid
K = lysine
W = tryptophan
This translates into similar proteins in these species, and indicates
that humans and chimpanzees may have had a common ancestor.
Since humans and chimpanzees have exactly same sequence, they
must be placed together. The gorilla differs by one amino acid, whilst
the orangu-tan by two, so it follows that the gorilla is more closely
related to humans.
This suggests vertebrates change over time. Like most amphibians,
reptiles and mammals, it has 4 legs but its fish-like tail and gills
suggest it lived in water. It is considered one of the no-longer missing
links – it shows us how land vertebrates could have evolved from
fish.
However, in order to find out what an ancestor looked like or how it
lived, the fossil record must be studied.
Such comparisons of amino acid sequences have been used to
determine evolutionary relationships in the primates (Fig 1).
Fossils can be accurately dated, so we know when the organism
lived and died. They allow a sequence of changes can be seen e.g.
the fossil record clearly shows:
Fig 1. Evolutionary relationships in primates
Oran-utan
Common
ancestor
Chimpanzee
Human
Gorilla
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the trend from quadripedal to bipedal locomotion
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the changes in hands which increased dexterity
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changes in jaws/teeth reflecting changes in diet
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changes in skull size and shape which indicates the evolution
of the brain
Bio Factsheet
201. Humans: evolution or creation ?
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Typical Exam Question
Homologous structures
The diagrams show reconstructed skulls of individuals of the
genus Homo
There are incredible similarities between very different groups of
organisms. The pentadactyl limb – or adaptations of it – are found
in very different organisms (Fig 3). This suggests that they
developed from a common ancestor.
Fig 3. The pentadactyl limb
mole
A
B
C
porpoise
(a) Which is the most modern skull? (1)
(b) What are the disadvantages of using the fossil record as
evidence for human evolution? (3)
horse
human
Markscheme
(a) Skull A. Humans have less prominent brow ridges and a
more domed cranium than our ancestors. The face is flatter
the jaw shallower and the teeth are smaller.
bat
(b) bodies/(soft) body parts are often not preserved;
require special conditions for preservation;
very few fossils are found / gaps in fossil record;
difficult to get a full picture from few parts/organisms;
Humans and chimpanzees are both primates. Many other primate
species are now extinct. Fig 4 shows one suggested relationship
between modern humans, some of the now extinct human-like species
and chimpanzees. The number by each species indicates the average
brain size in cm3.
The fossil record often consists of a few fragments of bones and
teeth and is certainly not complete.
The huge gaps in the fossil record are seized upon by creationists
who argue that scientists have insufficient evidence for human
evolution. However, even though scientists don’t completely agree
about some of the evolutionary relationships between one species
and another, they don’t accept that the missing fossil evidence
weakens the theory. They point out that:
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The fossil record is consistent with evolution
There is huge amounts of supporting evidence e.g. DNA, carbon
dating, and behaviour
There is no contradictory evidence
Millions of years ago
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Fig 4 Suggested relationship between modern humans and
extinct human-like species
Geographical distribution of living organisms
Organisms with common ancestry found in areas geographically
separated have different adaptations i.e. they show divergent
evolution; e.g. Darwin’s finches in the Galapagos Islands / New
World monkeys in America and Old World monkeys in Africa /
marsupials in Australia;
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Homo sapiens 1400 cm3
Homo neanderthalensis 1500 cm3
chimpamzee
400 cm3
Homo erectus 900 cm3
Homo habilis 550 cm3
Australopithecus 450 cm3
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the number (cm3)
indicates average
brain siize
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Typical Exam Question
(a) Name one homo species that became extinct less than 1 million
years ago.
(b) How can some of the information in Fig 4 be explained by Darwin’s
theory of natural selection?
(a) Neandertha/ erectus
(b) development of new species over time;
extinction of smaller brain size/less adapted species
more recent species show increasing brain size;
better adapted/ more intelligent more likely to survive;
able to pass on advantageous characteristics;
advantages may be language/tool making;
example of exception (Neanderthal or chimpanzee;
species over reproduce;
Organisms that live in similar habitats have similar adaptations i.e.
show convergent evolution e.g. streamlined shape of dolphins and
fish.
Answers
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Bio Factsheet
201. Humans: evolution or creation ?
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Brain size
Fig 5a and b show the estimated brain volume and body mass of some early hominids as deduced from their fossil remains.
Fig 5a estimated brain volume
Fig 5b estimated body mass
estimated body mass /kg2
estimated brain volume /cm3
Homo sapiens
1500
Homo erectus
1000
Homo habilis
Australopithecus
500
3.0
2.0
1.0
millions of years ago
0
Age/million years ago
Homo sapiens
Homo
rhodesiensis
0.6
0.8
1.0
Asia
Answers
1. (a) H. sapiens;
(b) H. sapiens dates back 200 000 years in Africa;
the oldest ancestor, H. ergaster, originated in Africa;
H. sapiens evolved from H. rhodesiensis, H. antecessor mauritanicus
and H. ergaster, all in Africa;
(c) H. erectus because it lived longer (1.5 million years compared to 700
000 years for H. antecessor/mauritanicus);
H. erectus because it lived more recently;
uncertain since climate during period of either species unknown;
uncertain since population size of either species unknown;
H. erectus (existed for a longer period) so may have had a greater
absolute number of individuals therefore chance of fossilization is
also greater;
0.4
Homo
erectus
Homo
antecessor/
manritanicus
1.2
1.4
1.6
0
2. (a)?we are able to treat most diseases
most people live and reproduce
all genes passed on
humans are able to control their environment
plenty of food/ temperature control
(b) many people of child bearing age die of AIDS
those who are more resistant to HIV survive
resistant people bring up more children
resistant characteristic spreads throughout population
1. Newly-discovered fossilized skulls from Ethiopia have led to
different theories about the origins of H. sapiens. The diagram
below shows one of these theories.
Homo
neanderthalenis
Australopithecus
However, most scientists still believe that we are subject to the
powerful evolutionary forces that have created and destroyed
many species over the past three billion years.
(a) Identify three aspects of Western lifestyle that could be used
to argue that we have overcome all the forces of natural
selection. (3).
(b) In 2007 in Africa 1.6 million people died of AIDS. Another 1.7
million became infected. Outline how AIDS may act as an
evolutionary force influencing human evolution in Africa.(3)
Practice Questions
0.2
Homo habilis
2. Some biologists believe a Western lifestyle now protects
humanity from the forces of natural selection. They suggest we
are no longer evolving.
Despite this and much other evidence, some people find it hard to
accept that humans have evolved from other species. Reasons
include:
• we seem to be different from animals ( they implicitly state that
humans are different from, rather than an example of an animal).
• only humans have language, self awareness, morality, highlydeveloped intelligence and technology, so it is highly unlikely
that we have a common ancestor with chimpanzees
• religious books such as the Bible describe creation
• the theory of evolution breaks a special relationship with God
• some people consider humans superior
• it is difficult to imagine the incredibly long timescale
Africa
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(a) Which species that shows the greatest geographic
distribution?(1)
(b) What evidence is there in the figure that human evolution
originated in Africa?(2)
(c) Would H. antecessor/mauritanicus or H. erectus be most
likely to provide the best fossil evidence?(2)
Note that the increase in brain size is much greater than the increase
in mean body mass. In other words, the brain volume to body mass
ratio has significantly increased over the last 3 million years. This
translates into a greater capacity for learning and greater intelligence.
Europe
Homo sapiens
Homo erectus
40
3.0
2.0
1.0
millions of years ago
The volume of the cranial capacity was measured using sand or
water in models of the brains. Body mass was estimated by
measuring the length of limb bones and extrapolating with the bones
of modem humans.
0
60
Homo
ergaster
1.8
Acknowledgements:
This Factsheet was researched and written by Kevin Byrne.
Curriculum Press, Bank House, 105 King Street, Wellington, Shropshire, TF1 1NU.
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