Author: Richard Dawkins
Preface
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This book is my personal summary of the
evidence that the ‘theory’ of evolution is actually a fact.
Chapter 1: Only A Theory
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Teachers in Britain
and Europe now face the same problems, partly
because of the American influence, but more significantly because of the
growing Islamic presence in the classroom…
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More than 40 per cent of Americans deny that
humans evolved from other animals, and think that we –and by implication all of
life- were created by God within the last 10,000 years.
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I shall be using the name ‘history – deniers’
for those people who deny evolution: who believe the world’s age is measured in
thousands of years rather than thousands of millions of years, and who believe
humans walked with dinosaurs.
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It is the plain truth that we are cousins of
chimpanzees, somewhat more distant cousins of monkeys.
Chapter 2: Dogs, Cows And
Cabbages
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Every animal is linked to every other animal.
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The wild ancestor of all domestic dogs really
does seem to be the wolf and only the wolf.
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All breeds of dogs are modified wolves: not
jackals, not coyotes and not foxes.
The main point I want to draw
out of domestication is its astonishing power to change the shape and behavior
of wild animals, and the speed with which it does so.
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Genes don’t blend, they shuffle.
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Any one of your eggs (or sperms if you are
male) contains either your father’s version of a particular gene or your
mother’s version, not a blend of the two. And that particular gene came from
one and only one of your four grandparents, and from one and only one of your
eight great-grandparents.
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Mutations are the random changes in genes that
constitute the raw material for evolution by non-random selection.
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I have no doubt that if you set your mind to it
and had enough time and enough political power, you could breed a race of
superior body-builders, or high-jumpers, or shot-putters, pearl fishers, sumo
wrestlers, or sprinters, or (I suspect, although now with less confidence
because there are no animal precedents) superior musicians, poets,
mathematicians or wine-tasters.
Chapter 3 : The Primrose Path To Macro-Evolution
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The human eye and the human nose went to work
on wild roses, enlarging them, shaping them, doubling up the petals, tinting
them, refining the bloom, boosting natural fragrances to heady extremes,
adjusting habits of growth, eventually entering them in sophisticated
hybridization programs until, today, after decades of skilful selective
breeding, there are hundreds of prized varieties, each with its own evocative
or commemorative name. Who would not like to have a rose named after her?
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Not all the work was done by insects – for some
flowers the pollinators that did the initial selective breeding were hummingbirds,
bats, even frogs – but the principle is the same. Garden flowers have been
further enhanced by us, but the wild flowers with which we started only caught
our attention in the first place because insects and other selective agents had
been there before us.
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Flowers that look plain to us may actually be
lavishly decorated with spots or strips for the benefit of insects,
ornamentation that we can’t see because we are blind to ultraviolet.
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Galapagos Islands , whose name comes
from a Spanish word for tortoise.
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Experiment specifically means that you don’t
just wait for nature to do something, and passively observe it and see what it
correlates with. You go in there and do something. You manipulate. You change
something, in a systematic way, and compare the result with a ‘control’ that
lacks the change, or you compare it with a different change.
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Selection causes evolutionary change.
Chapter 4 : Silence And Slow Time
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Coral reefs, too, have annual growth rings,
just like trees. Fascinatingly, these have been used to detect the dates of
ancient earthquakes. Tree rings too, by the way, tell us the dates of
earthquakes.
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Recognizably similar layers of sedimentary rock
occur all over the world.
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Do certain kinds of fossils, for example
mammals, appear only after a given date, never before? The answer of all such
questions is yes. Always yes. No exceptions. That is powerful evidence for
evolution, for it was never a necessary fact,…
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The origin of the earth at between four and
five billion years ago.
Chapter 5 : Before Our Very Eyes
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Although the vast majority of evolutionary
change took place before any human being was born, some examples are so fast
that we can see evolution happening with our own eyes during one human
lifetime.
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If you were to plot a graph of man height of
20-year-old men, from year to year during the twentieth century, you’d see in
many countries a significant trend towards getting taller. This is normally
reckoned to be not an evolutionary trend, but rather an effect of improved
nutrition.
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Bacteria offer another priceless gift to the
evolutionist. In some cases you can freeze them for an indefinite length of
time and then bring them back to life again, whereupon they resume reproduction
as if nothing had happened.
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Scientific research nowadays is often a team
effort.
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Like any poison, antibiotics are likely to be
dosage dependent. A sufficiently high dose will kill all the bacteria. A
sufficiently low dose will kill none. An intermediate dose will kill some, but
not all…………. When the doctor tells you to finish taking the pills, it is to
increase the chances of killing all the bacteria and avoid leaving behind
resistant, or semi-resistant, mutants.
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One of the nice things about science is that it
is a public activity. Scientists publish their methods as well as their
conclusions, which means that anybody else, anywhere in the world, can repeat
their work.
Chapter 6 : Missing Link What Do You Mean ‘Missing’?
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Forests: don’t provide good fossilizing
conditions.
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You have to believe we all came from a single
cell…
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Every one of the millions of species of animals
shares an ancestor with every other one.
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Once again, humans are not descended from
monkeys. We share a common ancestor with monkeys.
Chapter 7 : Missing Persons? Missing No Longer
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for Africa is
where our ancestors evolved, as we shall see.
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Molecular evidence shows that the common
ancestor we share with chimpanzee lived about six million years ago or a bit
earlier,
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What matters is that the links are no longer
missing. Intermediates abound.
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So, we have fine fossil documentation of
gradual change, all the way from Lucy, the ‘upright-walking chimp’ of three
million years ago, to ourselves today.
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I mean almost every fossil you find is
intermediate between something and something else.
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Australopithecus, Homo habilis, Homo erectus,
Homo sapiens – archaic Homo sapiens and then modern Homo sapiens – that’s a
beautiful series of intermediates.
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……the transition from fish to land-living
amphibians and reptiles.
Chapter 8: You Did It Yourself In Nine Months
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Unlike Adam, who was fashioned directly into
his adult form,
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Thyroid cells are quite different from muscle
cells, and so on, even though their genes are the same.
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Natural selection favours the survival in the
gene pool of the genetic mutations responsible for making crucial changes in
embryos.
Chapter 9: The Ark
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most, if not all, of the millions of
evolutionary divergences that have populated the Earth with such luxuriant
diversity began with the chance separation of two sub-populations of a species,
often, though not always, on either side of a geographical barrier such as a
sea, a river, a mountain range or a desert valley.
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Darwin island of Galapagos
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Think what the geographical distribution of
animals should look like if they’d all dispersed from Noah’s Ark.
Shouldn’t there be some sort of law of decreasing species diversity as we move
away from an epicenter – perhaps Mount Ararat ?
I don’t need to tell you that that is not what we see.
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There are similarities between the fossils of
South America, Africa, Antarctica, Madagascar ,
India and Australia
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And there are similarly telling affinities
between the fossils of northern North America and of Europe .
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Plate tectonic movements are important in this
chapter, because without them we cannot fully understand the distribution of
animals and plants over the continents and islands of the world.
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They don’t deny the shifting of the continents,
but they think it all happened at high speed very recently, at the time of
Noah’s flood.
Chapter 10: The Tree Of Cousinship
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the same set of twenty-eight bones, which can
clearly be labeled with the same names, is found across all the mammals.
All this is the same,
regardless of the fact that the shapes of the particular bones are radically
across the mammals.
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Not just the genetic code itself, but the whole
gene/protein system for running life, which we dealt with in Chapter 8, is the
same in all animals, plants, fungi, bacteria, archaea and viruses. What varies
is what is written in the code, not the code itself.
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Humans and chimpanzees share 98 per cent of
their genes.
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Different genes provide a marvelous spread of
molecular clocks, suitable for timing evolutionary change on scales ranging
from a million to a billion years,
Chapter 11: History Written All Over Us
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The hair-erection machinery is a vestige, a
non-functional relic of something that did a useful job in our long-dead
ancestors. Vestigial hairs are among the many instances of history written all
over us. They constitute persuasive evidence that evolution has occurred, and
again it comes not from fossils but from modern animals.
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You don’t have to dig very deep inside a
dolphin to uncover its history of life on dry land.
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Whales have no hind legs, but there are tiny
bones, buried deep inside them, which are the remnants of the pelvic girdle and
hid legs of their long-gone walking ancestors.
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As a result, brainy mammals contrive to
increase the area of the sheet while staying within limits set by the skull,
and they do it by throwing the whole sheet into deep folds and fissures. This
is why the human brain looks like a wrinkled walnut; and the brains of dolphins
and whales are the only ones to rival those of us apes for wrinkliness. Fish
brains don’t have wrinkles at all.
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‘Cold-blooded’ animals are not necessarily
cold. A lizard has warmer blood than a mammal if both happen to be out in the
midday sun in the Sahara desert.
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So numerous different kinds of animals that
live in the depths of dark caves where there is no light have reduced or lost
their eyes, and are, as Darwin himself noted, more or less completely blind.
Chapter 12: Arms Races And ‘Evolutionary Theodicy’
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Eyes and nerves, sperm tubes, sinuses and backs
are poorly designed from the point of view of individual welfare, but the
imperfections make perfect sense in the light of evolution.
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All the energy that drives life comes
ultimately from sunlight, trapped by plants.
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Trees are tall to overtop rival trees-of the
same and other species. Don’t misled when you see a tree in an open field or
garden that has leafy brunches all the way down to the ground. It has that
well-rounded shape so beloved of sergeant instructors because it is in an open
field or garden. You are seeing it out of its natural habitat, which is a dense
forest. The natural shape of a forest tree is tall and bare-trunked, with most
of the branches and leaves near the top.
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The Pacific
Coast
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Cheetahs are said to be capable of accelerating
from 0 to 60 mph in three seconds, which is right up there with a Ferrari, a
Porsche or a Tesla.
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Legs that are long and thin are good at running
fast. Inevitably, they are also good at breaking. All too regularly a racehorse
will break a leg in the heat of a race, and usually is promptly executed.
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The total amount of suffering per year in the
natural world is beyond all decent contemplation. During the minute that it
takes me to compose this sentence, thousands of animals are being eaten alive,
others are running for their lives, whimpering with fear, others are being
slowly devoured from within by rasping parasites,…
Chapter 13: There Is Grandeur In This View Of Life
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Darwin
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But today we are pretty certain that all living
creatures on his planet are descended from a single ancestor. The evidence, as
we saw in Chapter 10, is that the genetic code is universal, all but identical
across animals, plants, fungi, bacteria, archaea and viruses.
