THE NEED FOR THIS ESSAY
There can be few more intriguing and important scientific questions than: what is the origin of humankind? When I was a boy at a Roman Catholic school in the early 1960s, I had to learn the Catechism and essentially this offered a three-word answer to the question which was: “God made me”. I soon came to believe that this answer was as wrong as it was inadequate.
However, surveys repeatedly show that about 40% of Americans hold to the creationist view that God made human beings much in their present form at one time in the last 10,000 years. It would appear that around 20% of Britons believe something similar.
The problem is that, once one moves beyond mere faith to look at the scientific arguments, the alternative explanation to creationism (or its cousin intelligent design) – namely, evolution – is a complicated matter and few people have the desire or the time or the understanding to study the case for evolution.
Consequently there are very few brief, accurate and intelligible pieces of writing on the origins of humankind. This essay attempts to address that gap.
WHAT IS EVOLUTION?
Before setting out the evidence for evolution and considering some of the arguments advanced against it, it would be as well to have a clear understanding of what is meant by the biological term 'evolution'.
The theory of evolution was independently developed by Alfred Russel Wallace and Charles Darwin, but it was the latter who first set out the case in book form in his "On The Origin of Species" which was first published in 1859. In that book, humans were barely mentioned. It was only in "The Descent Of Man" published in 1871 that he spelled out how humankind too was the subject of evolution and shared an ancestor with the chimpanzee.
Evolution therefore is an explanation for the origin of all life forms or species: bacteria, fungi, plants, animals, humans. It holds that all life forms have the same origin and that one form of life evolves into another through a process known as natural selection. How does this work?
All life forms comprise cells which undergo a process of division. This process is subject to mutations – slight changes in genetic composition – which occur randomly. Most mutations are neutral or disadvantageous rather than potentially beneficial, if only because they are random and there are many more ways of becoming worse than of becoming better. Nature selects for preference those random mutations which confer on that life form a greater chance of survival and reproduction. The mutation might be a different shaped beak or a longer neck that makes it easier to access local foods or markings that make it less detectable to predators (effectively ‘camouflaging’ it) or faster speed to make it more able to outrun predators.
Where one population is isolated from another (that is, they cannot interbreed), species can and do develop different characteristics reflecting the local circumstances in terms of geography, climate, prey, predators and food supply. This was how Darwin noticed differences in types of finch and tortoise on the Galápagos islands.
The process has been dubbed 'the survival of the fittest' although this was not a term which originated with Darwin himself. Since this idea has been hijacked by so-called social Darwinists, it is important to understand that the term 'fittest' is not a value judgement but simply a measure of the likelihood of having living offspring – that is, the ability to survive and the ability to reproduce - and the process applies to individual life forms - such as an individual animal - and not to groups of life forms – such as Caucasian humans. So 'the survival of the fittest' is perhaps better expressed as the survival of the ‘best adapted’ to a given environment.
Although Darwin himself did not know this, the biological means by which these mutations conferring advantage are passed from one generation to another is particular genes in a gene pool. A gene is a length of DNA which is deoxribonucleic acid that contains the genetic instructions used in the development and functioning of (virtually) all known living organisms.
The process of natural selection is incredibly slow in terms of human life spans, but there has been plenty of time for natural selection to work, since the Earth is around 4.6 billion years old, self-replicating molecules emerged around 3.5 billion years ago, simple clusters of cells appeared about 800 million years ago, and the common ancestor of chimpanzees, gorillas and humans lived around 6-7 million years ago. So, in the natural world (as opposed to a breeding centre or a laboratory), changes - such as a longer neck or a faster speed or a larger brain - take a long time to evolve, so long that one cannot identify the point at which one species actually becomes another.
Natural selection can appear wasteful and cruel. Most species have not survived various mass extinctions. The most famous is the Cretaceous-Tertiary extinction of some 65 million years ago which resulted in the death of the dinosaurs. But the most devastating was during the Permian-Triassic period some 250 million years ago when 70% of land vertebrates and 96% of marine species were lost. Today, as throughout evolution, most animals die young and painfully either through starvation or predation. It really is a brutal competition for survival with the fittest most likely to survive and pass its genes on to the next generation. But it is vital to appreciate that this is not a plan or a design. It is an automatic process of natural selection by random mutation. If there were no such process at work, we would not be here to consider it.
Link: the process of natural selection as described by the Khan Academy click here
NINE ARGUMENTS FOR EVOLUTION
Argument 1: Evolution explains the similarity of species
Like any good scientific theory or law, evolution explains all the known facts in a consistent and convincing manner. Most especially, it explains convincingly how present day species are related to each other.
It explains the similarity – the technical term is homology – between the skeletons of all mammals, which share the same 28 bones although in different proportions, and how mammals have many similarities with other vertebrates including the basic features of their skeletons and their digestive, circulatory and nervous systems. It explains why the body plan of all crustaceans – lobsters, prawns, crabs and the like – is the same. It explains why the DNA code is invariant across all living creatures while individual genes vary.
Argument 2: Evolution explains the geographical distribution of species
Evolution explains why animals tend to live on the same continent as fossils that are probably their ancestors and why animals share the same continent with species that resemble them. Conversely, no frogs are found on oceanic islands because frogspawn is immediately killed by sea water.
Particularly striking is the evidence of life on oceanic islands formed by volcanic action and never connected to a continent – such as the Galápagos and Hawaiian islands. Evolution suggests that such locations would have few species because of the difficulty of crossing the ocean and that such places would have animal forms that are found nowhere else because the habitat is so distinct. This is exactly what we find: so on the Galápagos islands there are only just over 20 species of bird and 14 of those are finches and on the Hawaiian islands the number of species of the fruitfly Drosophila exceeds that found in the rest of the world.
Argument 3: Natural selection is analogous with other forms of selection
We are reinforced in our view that over time random mutations can through natural selection result in different types of life and different versions of animals because we observe that artificial selection - for instance, of cabbages, roses, pigeons, dogs and horses - and sexual selection - for instance between peahens and peacocks - does the same on a much shorter timescale.
Argument 4: Evolution is confirmed by scientific dating methods
We know that life has evolved over millions and millions of years and not a few thousand years because of scientific dating techniques such as the decay of radioactive materials and carbon dating. All these dating techniques not only reveal a very long process of evolution but are remarkably consistent in the dates that they offer us.
Argument 5: Evolution is confirmed by observation and experimentation
The most striking case is the ever-increasing resistance of bacteria to anti-biotics. Bacteria multiply fast and are present in enormous numbers so that mutations that are resistant to a particular anti-biotic can occur easily. The more we use anti-biotics, the faster bacteria can evolve to be resistant to them. Another example is the increased frequency of tuskless elephants because of the killing of elephants for their ivory. The explanation is that the elephants that were not killed for their tusks were more likely to survive and became a growing band proportionally while their offspring with genes that did not produce tusks also had a better chance of survival.
In 1971, a type of insect-eating lizard that was present on an island called Pod Kopište but not on the island of Pod Mrčaru – both islands being located off the Croatian coast – was transported to the second island where the lizards had a more vegetarian diet. In 2008, scientists found that the descendants of the transported lizards had significantly larger heads because they were eating more plant material. This was natural selection at work over a mere 37 years. [For more information click here]
An experiment conducted by the bacteriologist Richard Lenski and his colleagues at Michigan State University in the United States took a common bacterium called Escherichia coli and, through a series of ingenious techniques, replicated the effect of over 50,000 generations of the bacteria. The results were entirely consistent with the principles of natural selection through random mutation. [For more information click here]
Argument 6: Evolution is confirmed by the fossil record
Very few fossils had been discovered at the time of Darwin's original thesis, but it was clear from the theory that, if evolution is true, fossils of simpler forms of life should be found at earlier or lower levels of strata of the Earth and fossils of more developed forms of life should be discovered in later or higher levels of strata. This is exactly what the fossil record reveals. All fossils which have been found - and there are now very many - are in the correct temporal sequence. No fossil has ever been found in the 'wrong' sequence. Specifically we now have a rich supply of intermediate fossils linking modern humans with the common ancestor that humans share with chimpanzees.
You can view for yourself a selection of such fossils in most museums of natural history.
Of course, the fossil record is not complete and never could be especially for animals which are not susceptible to being fossilised, but the fossil evidence in many major animal groups is strong and becoming ever stronger.
Argument 7: Evolution is confirmed by the gene pool
Darwin did not know about genes which were first suggested by the Austrian scientist Gregor Mendel, although Mendel himself did not use the term which was only coined in 1909. A gene is a length of DNA that contains the genetic instructions used in the development and functioning of all living organisms. As the science of genetics has rapidly developed, we have become capable of mapping the genetic code of different life forms and identifying the incredible similarity in genetic composition of life forms which have common ancestors as explained by evolution.
This has enabled geneticists to say that humans and chimpanzees share 98% of their genes – although it is important to understand what is meant by such a statement. It does not refer to the number of whole genes but to the number of DNA 'letters' that match each other. The point is that shared DNA is confirmation of shared ancestry as set out in the theory of evolution.
Argument 8: There is an absence of design
If emergence of life was not the result of a process of natural selection through random mutation, then it might be that it was the result of a non-random process involving design which would suggest a designer (God). In fact, it is clear that there is no design. On the contrary, there many instances of imperfection.
A wonderful case occurs with the pouch of the koala bear which opens downwards instead of upwards as in a kangaroo, even though the koala spends its time hanging upright from trees. The explanation - provided by evolution - is that the koala is descended from a wombat-like ancestor who flung soil backwards, necessitating a pouch facing downwards. The most dramatic illustration that life was not designed by a beneficent God is that of the ichneumon wasp which paralyses a caterpillar and then lays eggs inside its body which hatch to produce young which proceed to devour the caterpillar alive one organ after another in an order which keeps the caterpillar alive (and therefore fresh) as long as possible.
A classic example of imperfection is what is called the recurrent laryngeal nerve which takes a bizarre route from the brain to the larynx in mammals and humans. Another example is the odd detour taken by the vas deferens - the pipe that carries sperm from the testis to the penis - in male humans. A third example is found in the sinuses of humans which has its drainage hole in the top rather than the bottom, a consequence of our shift from being quadruped to biped. Yet another example occurs in the eye - often represented by creationists as a marvel of design - where the retina is back to front, a defect that has to be corrected by the brain. In fact, the human body abounds with imperfections which can only be explained by the long process of gradual evolution and modification.
One more piece of evidence against any notion of design: the genetic code as formed by DNA has an enormous amount (the majority) of redundant DNA. Why is it there?
There are currently two possible explanations. The first view is that it must have coded for proteins no longer used by the descendant of the entity that did have use for that protein. If this is the case, it is not a good design. All these redundant genes (in every cell) take energy to create. What a waste. Hardly intelligent. The other view scientists are considering is that this redundant DNA may have something to do with the structural integrity of the DNA helix. But again it is not an elegant design for a structural solution and was probably the result of the DNA's long evolution to the stable structure it eventually formed utilising the redundant DNA for structural purposes. Proteins form complex structures using ionic bonds (electrical repulsion and attraction). So nature can be beautifully simple and unnecessarily complex - but that is evolution not intelligent design.
Over and above the routine imperfections to be found in the natural world, the absence of design (at least by a rational and beneficient God) is evident from the vast wastefulness and immense cruelty of nature. Most animals die early, without even having the opportunity to create offspring, and they frequently die cruelly, eaten alive or torn apart by another animal, or die slowly, wasted by disease or starvation. Not a sensible or kind design or indeed any design.
Argument 9: Evolution is a falsifiable theory
Like any good scientific theory or law, evolution is falsifiable by contradictory evidence. There has been no such contradictory evidence.
If one fossil was found in strata representing a period older or younger than one would expect to find it, then the theory would be massively challenged. This has never happened.
RESPONSES TO NINE ARGUMENTS AGAINST EVOLUTION
Counter argument 1: There is a missing link in the tree of life
There is no missing link. Since evolution is continuous and its speed varies enormously, in a strict sense all species are in transition and it is often difficult to identify categorically when a transition occurs from one species to another. However, since Darwin first enunciated his thesis, palaeontologists have discovered many intermediate forms between different groups of animals: between fish and amphibians, between amphibians and reptiles, between reptiles and mammals, and so on.
The fossil Archaeopteryx is one of the most famous, discovered in 1861, a mere two years after the first publication of "On The Origin Of Species". It had feathers like a bird, but teeth, claws and a bony tail like a dinaosaur. Ambulocetus, discovered in 1992, is known as the walking whale. It could walk on four legs on land and in water and heard by picking up vibrations through its jawbone like modern whales. Tiktaalik, discovered in 2004, is the link between fish and amphibian. It looked like a primative fish crossed with early four-legged animals and had lungs and gills plus fins that could support much of its weight [for more information click here]. Similarly Homo ergaster/erectus is the link between Homo habilis two million years ago and Homo sapiens today.
Of course, from the perspective of a strict creationist who is determined to oppose and misunderstand evolution, each new intermediate form simply creates an extra missing link. The point is that the tree of life is not a series of distinct links but a very gradual morphing from one form to another.
Counter argument 2: There are no fossils for intermediate animals such as a fronkey
Of course not, because monkeys are not descended from frogs. Equally humans are not descended from chimpanzees. No modern species is descended from any other modern species. Instead evolution postulates that monkeys and frogs share a common ancestor in the same way that chimpanzees and humans share a common ancestor. Indeed, if one goes back far enough in the tree of life, then every species shares an ancestor with every other one. going all the way back to the original cells that constituted the first forms of life on Earth.
Counter argument 3: There are gaps in the fossil record
Of course, there are. This is not surprising. It is the inevitable result of chance fossilisations, chance discoveries, and immigration events. The major reason for gaps is "stratigraphic discontinuities" which means that fossil-bearing strata are not at all continuous. There are often large time breaks from one stratum to the next and there are even some times for which no fossil strata have been found.
What is surprising and satisfying is how comprehensive is the fossil record. Scientists worldwide have unearthed some 200 million large fossils and billions of small fossils.
The biggest gap and the one most often quoted by creationists is the one that preceded the so-called Cambrian Explosion which saw the emergence of most of the main animal divisions. The period concerned was about 20 million years which seems large but occurred half a billion years ago. The explanation for the fossil gap here is probably that, before the Cambrian Explosion, most animals were soft-bodied and rather small and therefore not suitable material for fossils.
Counter argument 4: We do not have an explanation for the start of evolution
It is true that we have no evidence about what actually started the long process of evolution, although there are a variety of hypotheses for what is known technically as abiogenesis, most notably the iron-sulphur world theory (metabolism without genetics) and the RNA world hypothesis (RNA life-forms). [For more information click here]
If the start of evolution was a simple matter, presumably there would be many occasions of life around the universe – and indeed there might be (although we have no evidence for life anywhere else).
The essential point is that the absence of an explanation for the origin of evolution in no way invalidates the process of evolution. It simply means that we do not yet fully understand evolution and more thinking and discovery is required. If in the meanwhile, you wish to believe that it was God who started evolution, there is no evidence either way for such a proposition, although it is of course inconsistent with a literal interpretation of the Bible and the Koran.
Counter argument 5: Evolution could not create something as complex as the eye
In fact, it can and it has. Creationists believe that the eye could not 'simply' evolve because there is no use for intermediate stages. Surely, for instance, a retina is useless without a lens? In reality, a a retina is not useless without a lens and many types of invertebrate animals have simple eyes with no lens for the reason that such animals do not need to see clearly. Different groups of animals display a whole series of intermediates between simple light-sensitive receptors and variable types of complex devices that produce images of the world.
Indeed some creatures once had evolved eyes only for their descendants to go underground to search for food, shelter and security and then no longer need vision so, while they have kept their eyes, they are in fact are blind. Evolution can go back and forward - as further evidenced by mammals going back to the sea (this is why whales and dolphins do not breath through gills because they are descendants of land mammals and not marine life).
Counter argument 6: If evolution is a continuous process, why are we not still evolving?
We are – natural selection never stops and humans are still evolving. It is just that the slowness of the process compared to our lives makes it hard to notice. But, for instance, our diet differs from our ancestors and our teeth now do not need to be so strong, but any dental problems can now be addressed by dental care which somewhat 'interferes' with unconstrained evolution.
Counter argument 7: Evolution is contrary to the Second Law of Thermodynamics
At first, this might sound like a sophisticated, even a killer, argument - but only if you know nothing about the law or misunderstand it. The Second Law of Thermodynamics states that, in a closed system, entropy - that is, the state of disorder - increases. It is therefore suggested by opponents of evolution that evolution cannot be true because it involves life moving from the simple to the complex which is the opposite of entropy. In fact, quite simply evolution does not take place in a closed system because the Earth is constantly replenished by energy from the sun. So there is no contradiction.
Counter argument 8: Evolution is only a theory
There are two dictionary definitions of the word 'theory': one is a hypothesis proposed as an explanation and the other is a hypothesis that has been confirmed by evidence. Evolution is a theory in the second sense. It is massively supported by evidence which essentially makes it as strong a scientific law as any other. Like any law, it can be disproved by a single piece of evidence which is in contradiction to the law but, since the formulation of the 'theory' by Charles Darwin a century and a half ago, no such evidence has been adduced.
Counter argument 9: We should teach the debate
This argument implies that evolution and creationism are similarly valid scientific explanations for the origins of human life that should be offered for equal consideration. In scientific terms, there is no debate. There is massive scientific evidence for evolution and essentially there is no scientific evidence for creationism. Some people believe that the Holocaust never happened, but the evidence for the Holocaust is so compelling that no American or British school would 'teach the debate'.
The powerful arguments for evolution and the compelling evidence supporting them make this one of the strongest theories in all of science. All the counter-arguments are really weak and have no real force unless one prefers to rest on faith rather than evidence.
In all the circumstances, it is remarkable how many people - perhaps most especially in the United States - adamantly stick to the explanation offered by creationism and reject (often with some anger) the notion of evolution. But then many people believe many weird things and elsewhere I have examined why this is the case [for an explanation click here].
Last modified on 14 January 2014
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