Transcript Evolution - 10Science2-2010

Evolution
Year 10 Topic 4
Evolution

Nearly two million
different kinds of plants,
animals and microorganisms are known to
be currently living on
Earth. More are being
found each year. The
average time that a
species lasts on Earth is
about four million years.
Which means that, like
the dinosaurs, many
species are long extinct.

Evolution suggests that
all forms of life stem from
the same remote
beginnings and that the
different species we now
know have developed
gradually over millions of
years. The fossil record
clearly shows that through
time, life became more
complex.
Surviving in different
environments

In order to evolve, a species must survive.
Adaptations

Organisms survive and breed in their
environments because they have
characteristics suited to that environment.
Specific structures, functions and behaviours
increase their chances of surviving, at least
until the organism is able to reproduce.
These characteristics are called
adaptations. They are inherited and are
passed from parents to offspring.
Adaptations take many forms and can be
classified as either structural (where the
adaptation is physical), behavioural (where
the adaptation controls the way they act).
Structural adaptations

Many animals blend with their background, now
invisible to predators.

A few can
change
colour to
blend with
changing
backgrounds

Others
resemble
non-living
objects such
as leaves,
twigs etc

With some
animals it is
difficult for a
predator to tell
which end is
which. The
predator attacks
the wrong end,
giving the prey a
chance to
escape.

Some
extremely
colourful
animals warn
predators to
stay away,
because they
taste bad or
are
poisonous.

A tricky variation on
this is the ‘mimic’. The
mimic is not
dangerous to
predators, but has
copied the colourings
and shape of another
animal, so predators
avoid it.

Some animals
have features
that make them
look larger and
more frightening
to predators. For
example, the
neck frills of some
lizards can be
opened to make
the head seem
like that of a
much larger
lizard.
Behavioural adaptations

Some animals have learned to sit very
still or move slowly to avoid predators.

Others are
active only at
certain times
of the day or
year to avoid
unfavourable
conditions
such as
extremes of
heat or cold.

Some have learnt to use
tools to access difficult
food. For example,
chimpanzees commonly
use broken twigs to
extract termites.

Some collect and
store food for
future use.

Many larger
animals form
herds to
provide
protection
from
predators.

Adaptations serve many purposes. Arctic fish contain a
kind of antifreeze in their blood, allowing them to
survive in waters that would freeze the blood of other
fish. The long mane of a male
lion makes it appear larger to
opponents. This kind of
adaptation for intimidation is
common. Intimidation also
involves behaviours such as
puffing out the chest and
standing up as tall as
possible.
Plants also have adaptations

One orchid achieves
pollination by imitating
the shape, colour and
smell of a female bee.
When a male bee
attempts to mate with
the orchid, pollen is
transferred from
flower to flower.
The silvery
coloured,
narrow-shaped
leaves of the
wattle tree help
reduce water
loss by
evaporation. All
organisms have
adaptations that
assist their
survival in their
environment.
Variation
Although individuals within a
species are very similar, they
are not identical. Variation
occurs within all species. Much
of this variation comes from the
differences in genes each
individual inherits from their
parents.
These differences are the result of the random assortment of
chromosomes during meiosis, and the combination of gametes
(sex cells) during fertilisation. Further genetic variation occurs as
a result of mutations. Other variations come from environmental
factors such as the amount of exposure to the Sun and
differences in diet.
Variation and survival

The organisms best adapted to
their environment are the most
likely to produce offspring. Their
offspring will inherit these
characteristics. Over several
generations, individuals with
favourable characteristics will
become the most common. In
contrast, those with less
favourable characteristics will find
the environment inhospitable.
They will be more likely to die
before they get a chance to
reproduce and so will become less
common. We can say that
favourable characteristics are
‘selected’.

Variation in a species is important if
environmental conditions change. Some
individuals will have characteristics that
are favourable, allowing the species to
survive the change.
The Theory of Evolution
The theory of biological
evolution states that life on Earth
has changed over time. This
gradual development of different
species from a common ancestor is
called evolution.
It basically states that a species
has natural variation which
allows it to adapt to a wider
range of environments. The
best suited to their
environment will survive and
breed the next generation, this
eventually gives rise to new
species.
Alternatives to Evolution
Most societies have stories
about the origin and diversity
of life. Creation is the view
that regards the world and
everything in it as having
been made by supernatural
means, by a god or gods.
The ancient Greeks suggested
that the world grew out of
Chaos, a dark mass where
everything was hidden. From
Chaos emerged a god and/or a
goddess. The ancient world
was peopled by them,
producing other gods and
goddesses, and then mortal
men and women. The Biblical
account includes stories of the
creation of the Earth and all
life on it in six days.
There is also an account of the
first man, Adam, being created
from clay and the first woman,
Eve, being created from his rib.
Some people believe the events
happened exactly as stated.
Other people interpret these as
stories with symbolic meaning,
as teachings about the
relationships between God or
gods, the universe and humans.
The whole question of the origin
of life then becomes bound to
religious belief.
Early Theories of Evolution

Until the late 1700s most scientists
believed that the different types of
organisms and their characteristics
had been fixed for all time. This
idea of the ‘fixity of species’ was
questioned by the French naturalist
Georges Buffon (1707–88) and.
Erasmus Darwin (1731–1802),
who both suggested that one
species could change to another.
Jean Baptiste Lamarck
(1744–1829). believed that
organisms were guided through
their lives by a creative force
that enabled them to overcome
adverse environmental
conditions. Organisms adapted
through a struggle to survive.
In 1809 he stated:
‘Organs are improved with repeated use and
weakened by disuse. Any changes to organs
due to the environment ‘are preserved by
reproduction [and pass] to the new
individuals which arise’.

These changes are acquired
characteristics, which Lamarck thought
were then passed on to the offspring.
Giraffes, for example, stretched their necks to reach food
high in the trees. This acquired characteristic (a longer
neck) was passed on, so that offspring inherited the
characteristic of a longer neck.
Charles Darwin aged 22, took a
position as naturalist on the HMS
Beagle, a ship commissioned to
survey and chart the coast of South
America.
For the next five years Darwin
observed the geographical
distribution of plants, animals, fossils
and rocks in various parts of the
world. He became convinced that
species could develop from a
common ancestral type.
Darwin’s Finches

The Galapagos
Islands are about
1000 km off the coast
of Ecuador. The
islands were
effectively isolated
from one another by
strong ocean currents
and a lack of winds
blowing from one
island to another.
Darwin marvelled at the diversity of forms on these
islands. He also noted some similarity between island
organisms and mainland organisms.

Darwin found 14 species of finches, all with similar
colourings, calls, nests, eggs and courtship displays.
They differed, however, in habitat, diet, body size
and beak shape. Darwin believed these 14 species
had come from a common ancestor. He suggested
that a few finches had arrived on the islands at some
time in the past. These finches showed natural
variation in their beak shape. On one island, those
with beaks of one shape were better able to feed on
the cacti found there. Finches with other beak
shapes found it difficult to survive. On other islands,
other beak shapes gave some finches a feeding
advantage.
The birds most suited to
their island survived to
produce offspring, which
inherited that beak shape.
This is called ‘survival of
the fittest’. The ‘fittest’
were the birds that were
able to feed and reach
breeding age. The
characteristic that gave
some beak types an
advantage were ‘selected
for’. Over many generations, the birds on different islands became
sufficiently different from each other to be recognised as a
different species.

This shows how different beaks might
have been ‘selected’ for the food
available on each particular island.
Darwins explaination of
Giraffes
Challenging Darwin


Darwin spent 20 years collecting and
sorting evidence for his natural
selection theory of evolution. It was
1858 that Darwin presented his ideas
to the scientific world. He was
prompted to publish his work by the
publication of a paper by another
naturalist, Alfred Russel Wallace
(1823–1913).
Wallace had reached a conclusion
similar to Darwin’s—that evolution
occurs by natural selection. His
second paper on evolution
was presented jointly with Darwin’s
in 1858.
Darwin’s major work,
titled On the Origin of
Species by Natural
Selection or
Preservation of
Favoured Races in
the Struggle for Life,
was published in 1859.
Although all 1250 copies
of the first edition sold
out within a day, much
of the reaction did not
support him or his
theory.

Throughout England,
religious leaders denounced
his work as heretical or
against the word of God. The
biblical account held that
man was formed in the
image of God. How then
could he have apes as
ancestors?

Although the Church opposed
his theory, Darwin was given
a state funeral in
Westminster Abbey in 1882.
Neo-Darwinism

Darwin’s explanation that evolution occurs
through natural selection is one of the most
important theories of science and is still
regarded as being essentially correct.
Darwin’s theory can be restated in terms of
modern genetics. This is sometimes called
neo-Darwinism.

Evolution is natural selection based
upon the natural genetic variation that
appears in all populations.
Natural selection
Is the process in which the
environment ‘selects’ favourable
characteristics, reducing the
frequency of unfavourable
characteristics. This means that
after many generations of
selection, a species will become
better adapted to its
environment. Individuals will
become highly adapted if their
environment doesn’t change.
Except for mutations, each
individual will be very similar,
because the amount of variation
will have declined.
Environments are rarely constant,
however!
Suppose the environment suddenly
got colder for a couple of
generations of a particular animal.
Some individuals within the species
may naturally be better able to
tolerate the cold, having thicker
coats or some other favourable
characteristic. They are better
suited to the new, colder conditions
than the rest of their species. Over
time, natural selection would
increase the proportion of
individuals with this tolerance of the
cold and decrease the proportion of
those who don’t.

Natural selection takes
several generations to
become obvious and so
it is extremely difficult
to observe in large
plants and animals. It
is more obvious in
organisms that
reproduce quickly.
Bacteria and insects are
two organisms in which
natural selection can
occur quickly enough to
be observed.
Selection of peppered moths
Scientists noticed that populations of the
peppered moth, were changing from mostly
light-coloured to mostly dark-coloured forms

The change occurred during the Industrial Revolution, when
coal-burning factories produced a lot of pollution in the form of
soot. When on the soot-darkened trees, the light-coloured form
of the moth was easily seen by birds, their main predator. The
dark-coloured moth blended with the blackened background,
increasing its chances of
survival. The dark colour is an
inherited characteristic. Hence,
more dark-coloured moths
survived to produce darkcoloured offspring.
After clean-air regulations were
implemented, lichen began to
regrow on tree trunks and the trees
returned to their original paler
colouring.
Moth
populations in many of
these areas have shifted back
towards the light-coloured
forms
Selection and rabbit control

In Australia, rabbits overran the
land for many years. The
myxoma virus, carried by fleas
and mosquitoes, was released
in Australia in December 1950
to control the rabbit population.
Within two months, 90% of
rabbits in certain areas had
died. Ten years later over 99%
of infected rabbits were dead.
This means less than 1% of
rabbits infected with the virus survived. Ten years later, only 25%
of rabbits in those same areas would die as a result of the virus,
and around 40% of those infected with the virus would survive.

These dramatic changes were the result of natural
selection acting on the rabbits. The resistant rabbits
would have survived the initial myxoma spread, and
produced offspring with an inherited resistance. A
healthy rabbit may produce seven or more litters of
young per year, and therefore
within a few years the number of
resistant rabbits would have
increased dramatically.

Selection and diseases
There have also been several
well documented cases of
populations acquiring resistance
to introduced chemicals.
Mosquitoes, which carry the
diseases yellow fever and
malaria, were treated with
chemical pesticides.
By
natural selection, populations of mosquitoes with a natural
resistance to the pesticides developed over the 20-year period
following the introduction of the pesticides into their environment.
Similarly, many bacteria are now resistant to certain types of
antibiotics.

Superbugs
When penicillin was first
introduced it was very effective
in treating infections caused by
golden staph. Now, a new stain
of Staph is resistant to it as well
as around twenty other
substances, including antibiotics,
antiseptics and disinfectants.
Recently, several strains of Staph
have become resistant to the
drug of last resort—vancomycin.
If vancomycin fails, the death
rate from Staph will rise
dramatically.
Speciation

A species is defined as a
group of organisms that
normally interbreed in
nature to produce fertile
offspring. The formation of
a new species is called
speciation. Natural
selection over long periods
of time, combined with
other factors such as
isolation and mutations,
can lead to new species
forming.
Geographic isolation

The first step in speciation is
geographic isolation of the
populations. Suppose a particular
population of rabbits. If the
environments differed on each side
of the river, each population would
change through natural selection
and the occasional genetic
mutation. Eventually the two rabbit
populations would have their own
characteristics, sufficiently different
from each other to be called a
variety, or subspecies. Subspecies
appear different but are still
capable of interbreeding.
Reproductive isolation
If the isolation of the
populations was long enough,
the change might be
sufficient to make them
incapable of interbreeding.
They would then have
reproductive isolation.
At this point a new species
has emerged.
Factors that might cause reproductive
isolation are:
• a change in colour patterns so that
mates are no longer recognised
• seasonal differences in mating times
• a changed chromosome which prevents
the sperm of one group from fertilising
eggs of the other.
Types of evolution
Divergent evolution

The Galapagos
Island finches and
the geographically
isolated rabbits
illustrate the idea
that many new
forms can evolve
from a single
ancestor. This is
known as divergent
evolution.
The idea is that new
environments are inhabited,
causing the evolution of new
species. Divergent evolution
results in a phenomenon known
as adaptive radiation. As the
ancestral organisms adapt and
evolve in their different
environments, they take on new
forms. Australia’s marsupial
ancestors have evolved and
radiated into many different
forms, from tree-dwelling, fruiteating possums to blind, meateating underground moles, and
the more familiar kangaroos and
koalas.
Convergent evolution
Or convergence, occurs when organisms evolve and end up having similar
adaptations. This is due to:
• living in similar environments, and
• having similar habitats and lifestyles.
In similar habitats the same types of characteristics are ‘selected for’, resulting
in organisms that look similar despite having very different genes. These
organisms may have analogous structures, structures that look similar
but which have come from different ancestors. One example is the gliding
membrane found between the limbs of Australia’s gliding possums and also
found in the flying squirrels of North America, Europe and Asia.
Parallel evolution

A third type of evolution is parallel
evolution, which occurs where related
species evolve similar features while
separated from each other. The result is
organisms that look alike and have
common ancestry, but are found in
different locations.

Old and New World monkeys share many
features. New World monkeys like the
vervet (bottom left) have prehensile tails to
hold onto branches, whereas Old World
monkeys lack prehensile tails since they
have evolved to live on the ground.
Evidence for Evolution
The fossil record

Direct evidence for evolution
comes from palaeontology, the
study of fossils. The fossil record
from all over the world provides
evidence of continual changes in
life forms from over 3500 million
years ago until the present.
Fossils are the preserved
evidence of past life usually
found in sedimentary rocks.
Fossils may be the:
• actual remains of
organisms (e.g.
mammoths frozen
in ice, insects
trapped in a type
of sap called
amber)

hard parts of
organisms
(e.g. shells,
teeth and
bones)

impressions of
organisms (e.g.
hollowed casts,
moulds where
substances have
replaced the
organism)

evidence of
the presence
of organisms
(e.g.
footprints).
The ages of fossils, and the
rocks in which they are
found, can be estimated
using radioisotope-dating
techniques. These
techniques have enabled
scientists to devise a
geological time scale,
dividing the history of the
Earth into eras. These eras
are subdivided into
periods, which are further
subdivided into epochs.
Using the fossil record
The fossil record allows us to trace
major events in the history of life on
Earth. Life seems to have begun
around 3500 million years ago. The
first organisms were probably simple,
single-celled, anaerobic (no oxygen
was available) bacteria which fed on
organic compounds in the primitive
seas. Later, photosynthetic bacteria
and blue-green algae appeared,
releasing oxygen into the
atmosphere. This oxygen release
allowed ozone (O3) to form and
accumulate, screening out some of
the ultraviolet (UV) radiation. This
gave some safety to the newly
evolving organisms.
An explanation for the
appearance of life?
One hypothesis to explain the
initial appearance of life was
put forward by a Russian
scientist, A.J. Oparin, in 1924.
The early atmosphere is
thought to have consisted of
gaseous methane (CH4),
ammonia (NH3), hydrogen (H2)
and water vapour (H2O).
Energy from lightning,
ultraviolet rays or gamma rays
split some of these gas
molecules. New bonds formed
to create complex organic molecules, which collected in pools to
form an ‘organic soup’. Over millions of years this ‘organic soup’
became concentrated, more complex molecules formed and the
first cells appeared.

In 1953, S. Miller and H. Urey
tested the idea in a laboratory
experiment at the University of
Chicago. Electric sparks were
passed into a gas mixture that
was thought to be similar to
the early atmosphere of the
Earth. Organic molecules were
produced! No experiments,
however, produced a living cell.
The Miller/Urey experiment. Given suitable conditions
molecules can combine to form organic molecules.
More complex life evolves
Around 1500 million years
ago, organisms with more
complex cellular structure
appeared. Sexual
reproduction appears to
have begun at around this
time. Organisms
recognisable as animals
appeared around 600
million years ago.
Thousands of specimens of
these invertebrates have
been collected from
sandstone deposits at
Ediacara, in the hills north
of Adelaide. They are
possibly related to presentday jellyfish and
earthworms
From bacteria to humans
An abundance of fossils from the Palaeozoic era (570 to
248 million years ago) show the existence of bacteria,
algae, soft-bodied invertebrates and representatives from
all the major animal groups
we know today.
Characteristic organisms
from the earliest Palaeozoic
era were the trilobites. The
earliest known land
organisms (vascular plants)
appeared around 400 million
years ago.
The first land vertebrates
(amphibians) appeared slightly
later. At this time the greatest
diversity and number of species
lived in the sea. The Mesozoic
era (248 to 65 million years ago)
is often called the age of the
reptiles because of the abundance
and diversity of reptilian forms
(including dinosaurs) that lived in
this era. The earliest mammals,
flowering plants and birds also
appeared in this era.

Fossils from the most
recent era, the
Cenozoic era (from
65 million years ago),
show the increasing
dominance of
mammals and the
appearance of humans
(200 000 years ago).
A changing record
The fossil record
provides evidence
of continual change.
A vast number and
variety of species
have emerged from
the earliest life
forms. Whole
groups of organisms
have appeared,
become abundant
and then
disappeared.
Some of these changes include:
Dramatic climate change and altered sea levels may
have caused the disappearance of 50% of all shallowwater marine invertebrates around 225 million years
ago.
The impact of a large
asteroid, and
consequent dust
storms, are thought
to have caused the
extinction of the
dinosaurs around 65
million years ago.
Other organisms, like
club mosses and
jawfish, have
appeared, been
abundant, but now
survive in small
numbers only.

Others, like the
flowering plants,
insects, mammals
and birds, were
present in small
numbers for some
time, then became
abundant.

Mammals
increased
dramatically
after the
demise of
the
dinosaurs.
An incomplete record?

The fossil record is, however, far from
complete. Only a small proportion of the
plant and animal species thought to have
existed are preserved as fossils. While the
fossil history of aquatic organisms is
extensive and detailed, the fossil history of
land animals is far less so. Fossilisation is a
rare occurrence. Organisms must ‘fall’ into
conditions where decay does not occur. The
soft tissues of organisms usually do not form
fossils.
Fossilisation is more
likely in seas, lakes,
swamps and caves,
but unlikely on land.
Geological processes,
and human activity,
are constantly moving
and destroying the
sedimentary rocks
that contain fossils.

Fossil evidence shows an excellent record for the
evolutionary development of some organisms such as
the horse.
Transitional forms


Provide the links
between the major
groups, such as the airbreathing
crossopterygian fish,
and the bird-like reptile,
Archaeopteryx.
For many groups of
organisms there are
large gaps in the fossil
record, often with no
transitional forms being
found.
Anatomical studies

Comparisons of the
anatomy of various
plants and animals
provide indirect
evidence of their
evolution from
common ancestors.
The front flipper of a
seal, a cat’s paw, a
horse’s front leg, a
bat’s wing and your
own hand all look
different and perform
different functions.
However, they all
consist of the same
number of bones,
muscles, nerves and
blood vessels arranged
in a similar basic
pattern. The basic
pentadactyl limb (a
limb with five digits)
can be traced back to
the fins of certain fish from which the first amphibians are thought
to have evolved. These fundamentally similar structures are
called homologous structures. The differences seen in the
structures may reflect adaptations to different environmental
conditions. Their similarity strongly suggests a common ancestor.
The distribution of plants
and animals
Biogeography is the study
of the distribution of plants
and animals, both now and
in the past. As Darwin saw
in the Galapagos Islands,
the organisms found on
oceanic islands resemble
those living on the nearest
mainland, yet include
species found nowhere else.
As oceanic islands have
never been attached to the
mainland, their inhabitants
are thought to have
somehow arrived from the
mainland, to then evolve in
isolation.
Genetic evidence
The structure of DNA and the
genetic code provide us with more
evidence for evolution. Comparisons
of DNA are used to provide evidence
of how closely different species are
related. For example, the genetic
make-up of a chimpanzee is 98.5%
identical to that of a human. Gorilla
DNA matches human DNA except for
the last 2.6%. The genetic make-up
of other primates is also similar to
our own.
Human Evolution
Evidence from the
fossil record and other
studies supports the
theory that modern
humans evolved from
a common ape-like
ancestor. The
evidence suggests
that there have been
many species of
humans, some of
which have become
extinct, while others
evolved into modern
humans.
Humans belong to the order Primates
and have many of the features of the
primate group. Primates (including us)
have:
• forward-facing eyes that allow binocular
vision
• pentadactyl digits (five fingers/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
Humans are unusual, as we also:
• walk upright (are bipedal)
• have fewer and smaller teeth than
the apes
• have a flattened face
• have a very large skull capacity, and
large brain, about three times larger
than that of apes
• make and use tools
• use various verbal and visual
languages to communicate
• are self-aware.
Evolution of humans
Our distant relatives
 Dryopithecus, an ape-like animal
that first appeared 25 million years
ago. Ramapithecus, another apelike animal, appeared 14–16 million
years ago and lasted another 6
million years. Some believe
Ramapithecus to be the ancestor
of the Asian orang-utan, while
others see a relationship to other
apes and humans.


The first true ‘human-like’ fossils
belong to the genus
Australopithecus (meaning
‘southern ape’, after the first fossils
found in South Africa). They are
around 4–5 million years old..
These species were fully bipedal,
walked on two legs, and had a
brain size of 400 cm3, less than
one-third that of modern humans.
All fossil australopithecines have
been found in Africa. One of the
most famous is a 40% complete
skeleton of a female named Lucy.
More recent ancestors
The first clear
representation of the
Homo line is Homo
habilis (‘handy man’).
Fossils found in East
Africa dating to 1.5–2
million years ago reveal
major anatomical and
behavioural changes
from Australopithecus
afarensis. The brain size
was 50% larger, and
they used tools.
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
fossils are 1.5 million
years old. Homo erectus
had an average brain size
of 1000 cm3, lived in
caves and used fire.

The evolution of Homo erectus into Homo
sapiens (‘intelligent man’) is the subject of
considerable debate. Some maintain that
Homo erectus evolved worldwide into Homo
sapiens but retained local features. This gave
rise to different forms in different areas, such
as Asia and Africa. Others maintain that
Homo sapiens evolved in Africa, and spread
from there some 200 000 years ago. This
would mean that all present-day variation in
humans has arisen in the past 200 000 years.
Other fossil humans
Homo neanderthalensis
(‘Neanderthal man’), is thought to
be approximately 35 000–100 000
years old. The Neanderthals were
cave dwellers who used tools and
buried their dead, indicating some
religious beliefs. They 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 600 000 years ago.

‘Cro-Magnon man’ (10
000–40 000 years old)
was a nomadic huntergatherer who used tools
and developed art.
Anatomically CroMagnons were similar to
modern humans, but
more robust. CroMagnons lived in Europe
and the exact reasons
for their extinction are
not known.

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 survival—that is, a type of
cultural evolution occurs.

It is estimated that
of all the animal
species that have
ever existed, only
1% 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 200 000 years. With
cultural evolution, humans continue to acquire
knowledge, enabling them to exert more control over
their environment than any other species ever has, but
we have probably done more damage also.