Everyone likes to cling on to pet theories, even when the evidence stacks up against them. We saw how this happened when scientists proved that the earth went round the sun and was not the centre of the universe - some were imprisoned for daring to contradict the official views. The evolution debate is another example of how over-whelming evidence can be ignored just because it doesn’t fit in with strongly held beliefs.

Adam and Eve: the first humans on earth, created about 6,000 years ago?

Creationism
There are many who believe that the whole universe, including all living creatures on earth, was created by God in six days; that this happened some 6,000 years ago (some may put it back to 10,000); that humans and dinosaurs all roamed the earth together from about day six; that all humans and animals were wiped out by a great flood, except for Noah, his family and the animals he rounded up into his ark.

People who believe this are referred to as Creationists, sometimes as Young Earth Creationists.

EVOLUTION, CREATIONISM AND INTELLIGENT DESIGN
 

 

They continue to hold on to these views despite strong scientific evidence that the universe must have taken many billions of years to reach its present state; and that there has been life on earth for at least 3.5 billion years.    
In opposition to this is the theory of evolution.    
 
                 

This states that all animals (including humans) and plants have gradually evolved over a few billion years from very simple life forms.

This early life could have been a single cell which could duplicate itself, and which then gradually evolved, over hundreds of millions of years into a huge variety of more and more complex life forms.

Evolution could thus be defined as gradual change or development over time. The term usually refers to living things. But the way in which planets, stars, galaxies, and the universe form and change over time are also types of evolution.

   
The overwhelming majority of scientists agree that the theory of evolution best explains the origins of the great variety of life forms on earth, although there are still some differences of opinion as to the finer details of the process.
  Intelligent Design (or ID) is a modified, slightly more flexible form of creationism. It accepts that minor differences could evolve within species, but never that whole new species could evolve. Each species which exists, or which once existed, therefore has to have been created. ID also accepts that life on earth could date back much earlier than 6,000 years.
Natural Selection    
In the 1830’s the biologist Charles Darwin studied the variations among the plants and animals on the Galápagos Islands off the coast of Ecuador, and came to the conclusion that natural selection was the basis for evolution, i.e.    
     
  Only those species which can adapt to their changing environment survive to breed and pass on their genes.
     
Charles Darwin 1809-1882
 
     
Survival of the fittest
   
The giraffe and its long neck provides a possible illustration of natural selection at work.
Perhaps the ancestral giraffes, millions of years ago, had shorter necks and legs. But, as with all animals, there was variation within the species: some giraffes were taller than others. Then when food was scarce, those animals with longer necks and legs were at an advantage, as they could reach the leaves which were higher on the trees. These were the animals which would survive and produce more offspring. (This is referred to as survival of the fittest - i.e. those most fit to survive.) Shorter animals were at a disadvantage and were less likely to survive and pass on their ‘short’ genes.

Fit in this context means the best suited or best adapted, and not fit in an athletic sense.

Selection just means living long enough to pass on your genes - longer than others of your species with less useful genes. One can see how, after many generations of this natural selection, and over a very long period, the present-day giraffe could have evolved.

The same could be said about the evolution of the polar bear, the camel, the shark, the chameleon, humans and indeed every species that has ever lived.

 
EVIDENCE IN SUPPORT OF EVOLUTION    
Most of the evidence comes from the fossil record.

What are fossils exactly?
Fossils are any traces of animals or plants that lived long ago. They provide evidence of how today’s species have changed and developed over millions of years.

Most fossils are found in layers of rock. This can tell us not only what the creature may have looked like but also approximately how long ago it lived - generally, the deeper the fossil the older it is.

    Even though the fossil record is not complete (and probably never will be) it can still give us a good overall picture of evolution at work. What unfolds before us, through the fossil record, is a progressive sequence, leading from ancient, simple organisms to modern, complex forms.
     
    Changes over time in the bodies of animals

A good example is the evolution of the horse:

The fossil record clearly shows how adaptations took place over tens of millions of years (see diagram below). Four splayed out toes of 60 million years ago becomes three toes 40 million years ago, one large and two small toes 30 million years ago, a slender hoof about 10 million years ago, and finally the thicker, more robust hoof of today.   The fossilised bones of horses show how the horse could have evolved. From the fossils we can put together a family tree. About 60 million years ago the ancestor of the horse was very small - about the size of an average dog. They had splayed out toes, presumably to prevent sinking into the mud. As the marshy land gave way to harder ground the horse’s toes became fused into a single hoofed foot.

 

Evolution of the horse

 
     
Vestigial Structures
(Latin: vestigium = footprint)

These are structures in animals which have no apparent purpose, and appear to be ‘left-overs’ from our evolutionary past.

It is difficult to see these vestigial body parts as anything other than left-overs (or relicts) from distant ancestors. They show clearly how some species are related to others, and provide strong evidence for shared ancestry.

  Homologous Structures
(Greek: homos = same, locus = place)

The forearms of a cat, bat, whale and human have different functions i.e. are used for different purposes (walking, flying, swimming, grasping) and yet they are composed of exactly the same bones, just arranged differently and with alterations in length or shape. (Don’t forget that whales are mammals and are believed to have moved from the land back into the water.)

These related structures in different species are referred to as homologous structures. They are evidence that these animals were descended from a common ancestor.

For example
  • the hip bones and rudimentary hind legs of pythons, anacondas and boa constrictors (inside their bodies)
  • the pelvic bones of some whales, as well as tiny limbs, inside their bodies which were once hind legs
  • the finger-nails on the fins of manatees (huge sea mammals, sometimes known as sea-cows) - evidence that its fins evolved from hind legs
  • the eyes in totally blind cave-dwelling bats
  • the appendix in humans, which not only has no evident purpose, but can even be dangerous, sometimes becoming infected and inflamed. It is, however, related to body parts in other mammals, where they do have a purpose relating to digestion.
 
There are innumerable other examples
  Embryos

The embryos of very different species are often strikingly similar to each other. The slugs in the garden and the giant squid in the ocean seem to be completely unrelated. Yet the similarity of their embryos is evidence that they came from a common ancestor. There is also a striking similarity between the embryos of humans, other mammals, birds, fishes and even frogs!

   
Could there be any better explanation for this than that the bird, the whale, the bat, the cat, the human, the crocodile and the whole menagerie, all share an ancestor if we go back far enough?
  The case of the two missing digits

An adult bird has a 3-digit, rather than a 5-digit limb in its wings. This presents us with a minor mystery, bearing in mind that even most 4 legged reptiles (which evolved earlier than birds) have 5 digits in all 4 limbs.

A mystery, that is, until we examine the bird’s embryo.

There we find the missing digits!

Limbs in the bird embryo have 5 digits, but two are lost somewhere along the way (presumably because they were unnecessary and a hindrance to survival).

Selective Breeding

We’ve seen what happens in natural selection - when nature selects those characteristics which help the organism to survive.

Selective breeding is when humans artificially do the selecting.

We decide which characteristics we want, and only those plants or animals which have those characteristics are allowed to breed. It may be sweetness in plums, disease resistance in potatoes, redness in strawberries, the quality of milk in cows etc.

 
Why is this evidence of evolution?

Dogs have been selectively bred from wolves for only a few thousand years, and already dogs such as the Pekinese and the Daschund are unrecognizable from their ancestors.

 
If such changes could happen in a few thousand years, imagine what could happen in a few million!
     
Just another animal?  
Human evolution

When Darwin published The Origin of Species in 1859 there was very little fossil evidence to suggest that humans had descended from an earlier form of primate (the family of primates includes lemurs, monkeys, apes and humans), and many prominent scientists were very sceptical. The evolution of butterflies, birds and other animals was one thing, but humans were quite another matter. We tend to forget that we too are animals!

Darwin was nevertheless confident that the evidence would be found, and in his next book, The Descent of Man (1871), he explained why he believed we were related to apes. Darwin’s predictions were accurate and many fossil specimens have since been discovered which cannot be labelled either as belonging to modern humans (homo sapiens) or to apes. These specimens have been well dated. (See dating methods, below).

They reveal a branching tree, with one branch leading to modern humans. The suggestion is not that we are descended from the apes of today, but rather that apes and humans have a common ancestor which lived perhaps seven million years ago, although time estimates vary.

The diagram above is misleading. It looks as though we humans are the peak, the pinnacle, the final stage, the crowning achievement of the evolutionary process. But this is not the case.

Sadly, we are not necessarily the pinnacle of anything; for the implication of Darwin’s idea is that we are just another animal.

  The only real difference between us and apes is that we have developed an even more complex nervous system, along with a relatively larger brain. In any case, like every living thing we are probably still evolving.

This difference is of course not to be sneezed at. It has enabled us to write magnificent music and literature, to invent computers and Concorde, to put people on the moon, and of course to send messages through cyberspace! But for the rest - with our anatomy, feelings, basic morality, codes of behaviour, bodily functions, the ability to communicate, to laugh, to play, to use tools etc., we have an enormous amount in common with the other great apes. (1) The differences are a matter of degree. We share with chimpanzees about 94% of our DNA, or genetic make-up.

Moral awareness in animals...
and even petty jealousies!


Feelings of compassion, loyalty, love, mourning and petty jealousies are in evidence among apes (and even dogs and elephants) as in humans. Even buffaloes can show moral awareness and great courage, for example by stopping in their tracks while in full flight from lions, turning around and heading back to rescue one of their calves from the lions. (Google You Tube “Battle at Kruger” to see a fascinating battle between buffaloes, lions and a crocodile.)

Other studies of animals living together, such as vampire bats, also show a basic sense of morality, and social codes or rules of behaviour. Animals that break the rules are punished by being attacked, thrown out of the community or not helped in time of need. Chimps and bonobos have an even more developed sense of what is and what is not acceptable behaviour. It seems therefore that it’s not just our bodies which have evolved, but our sense of right and wrong.

 

Chimps comforting each other at a time of loss
Anger and outrage ...

The idea of human descent from apes was of course hotly debated in Darwin's day, but now there is little disagreement among scientists, apart from in the details. Darwin was well aware of the anger and outrage his theory would provoke. He almost felt guilty about it and remarked to a friend that publishing it was ‘like confessing a murder’. Many reviewers of his book considered it to be blasphemous, since it contradicted the biblical view of creation.

... and in the right corner the Bishop of Oxford

At a public debate on June 30th, 1860, Samuel Wilberforce, Bishop of Oxford, so the famous story goes, was facing the prominent scientist Thomas Huxley. The bishop poured scorn on Darwin’s theory. We do not have the exact words, but according to one report it went something like this:

 
The bishop: ‘Pray Mr. Huxley, is it through your grandfather or your grandmother that you claim descent from a monkey?’ (much laughter)   Mr. Huxley: ‘I would rather be descended from a monkey than from a man who uses his great gifts to obscure the truth.’ (Gasps of shock and amazement. One woman faints.)
Should creationism be taught in schools as part of the science curriculum?

The creation/evolution issue is more than just an academic or intellectual disagreement. Secondary schools in Britain have recently been lobbied by a creationist group called Truth in Science. Their pack, which includes a DVD, contains well designed, attractive, colourful materials, and mounts a strong attack on Darwin’s ideas. Inevitably, some hard-pressed teachers have been tempted to make use of it.

The Department for Education and Skills has warned schools about the pack: ‘While students are encouraged to consider alternative scientific theories, Intelligent Design is not one of them, for the simple reason that [it] is not a science... The fossil record is evidence of evolution. Creationism and ID are not scientific theories.’ They are based on faith and not scientific method.

The Royal Society agrees: ‘The theory of evolution is supported by the overwhelming majority of scientists, based on evidence acquired through experiment and observation... It would therefore be misleading for school pupils to be given the impression that there is scientific controversy.’ (Professor Michael Reiss, Director of Education, Royal Society).

Although Intelligent Design ignores the most basic principles of science, it does use scientific language, and so qualifies to be called a pseudo-science.

A bit like the stork theory in a sex education course? Scientists are disturbed that an argument, dressed up in scientific language and alluringly presented, but with no scientific credibility, is being offered to school children; and believe that it has no more right to be included in the biology curriculum than alchemy has to be included in chemistry, astrology in an astronomy course, or the stork theory in sex education classes.
Creationism and intelligent design are not science because they do not use the methods of science. They do not offer hypotheses which can be changed in the light of new data or demonstration of error. With science any hypothesis or theory can always be rejected or modified in the light of new evidence. Since creationism has its origin in sacred texts rather than scientific discovery, to question it is considered to be blasphemous and disloyal to God.    
     
Some common arguments against evolution    
     

There are too many gaps and missing links in evolution, and not enough transitional species!

 

A great many transitional forms and anatomical structures have in fact been discovered.

To mention a few:

     

Ambulocetus natans - a good example of a possible transitional species between land mammal and whale. (One fairly complete specimen and several partial skeletons found in Pakistan.) It looked like an enormous otter, but was probably an early whale. (Whales are mammals, believed to have moved from the land back into the water: i.e. to have evolved from land- into sea-creatures.) It had a long, low body and short, powerful limbs. Its feet had long, probably webbed toes, each ending in a tiny hooflet, and its tail was slightly flattened to help it swim. The eyes and nostrils were on top of its skull, allowing it to see and breathe whilst partly submerged. Other anatomical structures, such as in the ear, link it to the whale.

 
Archaeopteryx (meaning ancient wing) - a bird, but with clear reptilian features. (Seven specimens found so far.) It shows how reptiles, possibly dinosaurs, could have evolved into birds. Anti-evolutionists have dismissed it as merely a bird and not half-bird, half-reptile. However, unlike modern-day birds, it had teeth, three claws on each wing (as well as hind legs), a flat breast-bone, belly ribs and a long bony tail. Its skull, lack of horny bill, and certain bone structures were also closer to dinosaurs than birds. On the other hand, in common with modern birds, it did have feathers, a lightly built body, hollow bones, a wishbone and a reduced number of fingers.
     
Australopithecus, Homo Habilis, Homo Erectus and Homo Heidelbergensis and other creatures whose physical features show them to be neither ape nor modern human. Creationists argue that these fossils are simply the skeletons of apes or diseased humans, but there are too many which fall into neither category, human or ape, for them all to be dismissed in this way.
  Tiktaalik roseae - a good example of transition between fish and land animal, this was a giant 375 million year old fish, 9 feet long. (Several specimens found in the Canadian Arctic.) In its forward fins the scientists found evidence of limbs in the making, and the beginnings of digits, wrists, elbows and shoulders. The fish also had a flat skull, more like a crocodile, and a neck, which allowed it to swivel its head (a most un-fish-like ability!)
     
    Horses - a good example of how size and limbs can change over many millions of years.
     
This argument against evolution is sometimes called irreducible complexity, and the argument is that some complex systems appear very unlikely to have been produced by numerous, successive, slight modifications.  

Evolution cannot explain complex structures such as the eye. They could not have evolved by chance or by random mutations. Bits of the eye would be useless on their own, so it couldn’t have evolved bit by bit, but would have had to be created as a whole, in one go.

     
The eye could indeed have evolved piecemeal or bit by bit. It probably began as a single light sensitive cell, evolving into the complex eye of today through hundreds of intermediate steps. Many of these intermediate steps still exist in nature and can be seen today in many animals with simpler nervous systems. A crude sensitivity to light is better than no sensitivity to light, 1% vision is better than no vision, and 65% vision is better than 64% vision. Creationists also ask: ‘How could a wing have evolved piecemeal? What use is half a wing?’ In fact half a wing certainly could be useful. Primitive wings can be seen in action today with certain squirrels, frogs and other animals which are able to glide through the air.  
     
Science has developed reliable ways of working out how old fossils and rocks are. We can go back to the very beginnings of life on earth, over 3.5 billion years ago, or we can calculate the age of a Roman sandal, a piece of wood or a skeleton as ‘young’ as 1,000 years old.  

Dating methods are unreliable. How can we be so sure of the age of fossils, rocks, bones etc!?

Radiometric dating
Used for the dating of rocks. Elements such as potassium, rubidium and uranium are found naturally in rocks and have radioactive isotopes which decay extremely slowly. The isotope decays at known rates, and so the age of the rocks can be worked out by measuring the amount of the isotope that is left. This would, of course, also give the age of any fossil remains in the rock.

Potassium (which decays into argon) can be used to date rocks more that 100,000 years old; Rubidium can be used for rocks more than 10 million years old. Uranium (which decays into lead) and Thorium can be used for rocks more than 20 million years old. This would be good for the dating of dinosaur fossils embedded in rocks, but not for a woolly mammoth!

   
Dinosaur fossils - suitable for radiometric dating (but not radiocarbon dating)
 
Radiocarbon dating (or carbon dating)
This is a form of radiometric dating, used only for dating organic materials (i.e. things that were once living such as bone or wood). All living things have carbon-14 (the radioactive isotope of carbon) in them. As with the uranium or potassium isotopes, carbon-14 decays at a known rate, and so the age of the material can be calculated. It would be ideal for materials, such as a Neanderthal skeleton, up to about 70,000 years old, but not much use obviously for dinosaurs.
     
Stratigraphy (stratum = layer)
This looks at how deeply a fossil or artefact is buried within layers of sedimentary rock. Newer layers are formed on top of older layers. Generally the deeper the layer the older it is. If two artefacts or fossils are found in the same layer, they are assumed to come from the same time period.

This does not give an absolute age of the fossil or rock, simply an age relative to other fossils above or below it. The age can, however, be tested against the other dating methods which do give an absolute age.

A high level of consistency and reliability has been found in these methods of dating - consistency between as well as within each method. Different tests on the same rock show the same results. All these methods of dating provide clear evidence in favour of evolution.

 
     

Evolution cannot be called a science because it is not based on experiment or direct observation - it’s just an inference!

  It is true that no-one has seen, for example, the evolution of one-toed horses from three-toed horses, and that’s why evolution is still referred to as a theory.
 
The tiny fruit fly: ideal for study - cheap, prolific, easy to breed and with huge chromosomes
  But that does not mean that we cannot be confident that horses evolved.

Science is practiced in many ways besides direct observation and experimentation. Much scientific discovery is done through the forming of hypotheses and predictions which are then tested against the enormous pile of evidence which already exists, and which is still being found.

Moreover we can see evolution happening today, for example in viruses and fruit flies - organisms with very short life-spans, which we can observe changing over many generations. Such experiments provide further support for evolution.

If a theory is capable of explaining the evidence, and is not refuted by any evidence, then it will be accepted with increasing confidence by scientists.

     

Why is it that monkeys have stayed monkeys and have not evolved into a more advanced species? And why has the shark stayed much the same for more than 200 million years?

   
   
Well, if it ain’t broke, don’t fix it!

Animals only evolve if they need to adapt to changing conditions. There are roughly 350 species of sharks today. Those that have stayed much the same over 200 or even 300 million years have simply not needed to adapt. Their environments have not significantly changed and they have been perfectly well adapted to survive in that environment. The same applies to those monkeys or apes which have stayed much the same for a few million years - they have been well suited to survive in their habitat.

 


The shark: no need to change, even over 300 million years, if you’re well adapted to survive just as you are!
   

For at least one group of early apes, however, changes in their habitat several million years ago will have forced them to evolve new physical characteristics - larger brain, the ability to walk on two legs, better use of hands etc. in order to survive.

We do not know what the exact sequence of these changes were, or what the changes in habitat were, and different theories have been put forward.

The loss of jungle and forest as a result of climate change, probably had a lot to do with it.

Could anything refute the theory of evolution?

Lots of things could!

The theory would take a severe, even a knock-out blow if, for example, a human or a monkey fossil were to be found in the same sedimentary rock layer as a dinosaur fossil; or if a fossilized bird were found among the trilobites. About 1,700 different species of trilobite (which look a little like woodlice) have been discovered, and none has been dated to any time other than the late Palaeozoic era, which ended about 245 million years ago. The earliest birds date to about 200 million years ago.

However, no such anachronisms have been found, and will almost certainly never be found. This is the kind of prediction which palaeontologists can confidently make, but not creationists. It also shows how one dating system (e.g. stratigraphy) supports another (e.g. radiometric dating).

 
‘I cannot possibly believe,’ wrote Darwin in 1868, ‘that a false theory would explain so many facts.’
 
     
Noah’s Ark

If we accept the biblical version of creation, which is in the first chapter of the Bible (Genesis), do we not also have to accept some of the related stories in the same chapter? These include the story of Noah’s Ark as well as a few other highly improbable happenings.

   
God regrets having created humans, because they were so wicked, and decides to wipe them out. In addition, all the beasts, birds and insects must also go, although it is not clear why they deserved to die. He does this by causing a great flood:  
‘And God saw that the wickedness of man was great in the earth ….And the Lord said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.’ (Gen. 6: 5-7)
So that all his creation is not lost, however, God orders Noah to round up two of every kind of mammal, bird, reptile, insect etc. and assemble them in his boat, along with his family, so they can be rescued and make a fresh start after the flood. ‘…and every beast…. and all the cattle…, and every creeping thing that creepeth upon the earth…and every bird of every sort. And they went in unto Noah into the ark.’ (Genesis 7: 14-15)

The practical problems facing poor Noah would have been considerable. He would, presumably, have had to include many species of rodent, many species of snake, several kinds of rhinoceros etc! And how on earth did the Antarctic penguins survive the journey to the ark through the heat of Africa and the Middle East? Not to mention the poor South American sloths, who move extremely slowly and had to cover a vast distance to get to the ark, and who were very lucky not to have been left behind!

Concluding thoughts on the biblical version of creation

Other cultures and other religions, whether in ancient Greece, India, Africa, South America or elsewhere, all have their own creation myths. They are beliefs which have been written down hundreds, even thousands of years ago, or passed down by word of mouth over many generations. They are all different from each other and obviously cannot all be right. None has any better claim to be believed that any other. Why indeed should the Christian creation myth (for example) take precedence over any others?

 
The scientific approach, on the other hand, does not depend upon legend, cultural mythology, or the visions or revelations of ancient prophets. It depends rather upon what can be observed, tested, subjected to the scrutiny of others and retested. The process does not stop, and scientific theory can always be modified or rejected in the light of new evidence. Sometimes a theory, such as evolution, is supported by such a huge accumulation of evidence that almost all scientists accept it.

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