Predictably, the much-hyped distinction between micro-evolution and macro-evolution is becoming a hot favourite with creationists. It is easy to see why they have latched onto it, but actually it is an overrated distinction. This point is admittedly controversial, but many of us believe, in any case, that macro-evolution is nothing more than micro-evolution stretched out over a very long timespan. Let me clarify the matter.
Sexual reproduction sees to it that the genes of a population are a shuffled mix – the ‘gene pool’. The range of individual bodies that we see at any one time is the outward and visible manifestation of the current gene pool. As the millennia go by, the gene pool may gradually change. Some genes become gradually more frequent in the pool, others less frequent. And the range of animals that we see changes accordingly. Perhaps the average specimen becomes taller, or shaggier, or darker in colour. They don’t all become taller, there is still a good range of heights, but the distribution is shifted in the taller (or shorter) direction as the frequency profile of the gene pool changes.
That is micro-evolution, and a good deal is known about the underlying causes. Genes may change in frequency as the result of various chance processes. Or they can change in frequency in a more driven way, as the result of natural selection. Natural selection is the only known force that can produce improvement and the illusion of design. But, insofar as evolutionary change is not change for the better, there are plenty of other forces that might drive micro-evolution. For the moment, I shall talk of natural selection.
Individual animals with certain qualities – say shagginess in an encroaching ice age – are slightly more likely as a result to survive and reproduce. Therefore the genes that made them shaggy are slightly more likely to increase in frequency in the gene pool. This is why animals and plants become good at surviving and reproducing. Of course, what it takes to survive and reproduce varies among different species and in differing environments. The mole gene pool becomes loaded with mutually compatible genes that flourish in small furry crawling bodies digging for worms underground. The albatross gene pool becomes loaded with a different set of mutually compatible genes that flourish in large feathered bodies skimming the waves of the great southern oceans.
That is micro-evolution and our creationist friends are admitting that they have become reconciled to it. Instead, they are pinning their hopes on macro-evolution which, they have been encouraged to believe, is something completely different. It may be something completely different, but I doubt it. The great American paleontologist George Gaylord Simpson believed that macro-evolution is just micro-evolution writ large, writ slow and writ gradual over a sufficiently large number of thousands of generations. I agree with him, and am increasingly impressed by the speed with which gradualistic selection can accumulate to forge dramatic change. See, for instance, Jonathan Weiner’s account, in The Beak of the Finch, of the research by Peter and Rosemary Grant on rapid evolution in ‘Darwin’s Finches’ of the Galápagos Islands.
What is the alternative to the Simpson view? Some modern American paleontologists make much of an alleged ‘decoupling’ between micro-evolution – the slow, gradual change in gene frequencies within a gene pool – and macro-evolution, which they see as a relatively abrupt springing into existence of new species. Except insofar as I shall return to the matter when dealing with other sentences from the Alabama Insert, it is not necessary to air these controversies. They are matters of detail, which do not bear upon the fact of evolution itself. For the moment I’ll simply record the justified annoyance with which the leading exponents of decoupled macro-evolution and ‘punctuation’ view the creationists’ attempts to hijack their brainchild. Stephen Gould, for example, says:
Since we proposed punctuated equilibria to explain trends, it is infuriating to be quoted again and again by creationists – whether through design or stupidity I do not know – as admitting that the fossil record includes no transitional forms…Duane Gish writes, ‘According to Goldschmidt, and now apparently according to Gould, a reptile laid an egg from which the first bird, feathers and all, was produced.’ Any evolutionist who believed such nonsense would rightly be laughed off the intellectual stage; yet the only theory that could ever envision such a scenario for the origin of birds is creationism – with God acting in the egg…I am both angry at and amused by the creationists; but mostly I am deeply sad.
I agree, but I incline towards being angry more than sad or amused.
Evolution also refers to the unproven belief that random, undirected forces produced a world of living things.
It is remarkable how common is this travesty of the Darwinian theory. Any idiot can see that, if Darwinism were really a random force, it could not possibly generate the elegantly adapted complexity of life. It is no surprise, therefore, that propagandists with their own reasons for wishing to discredit the theory would put it about that Darwinism is nothing more than random ‘chance’. It is then easy to ridicule the theory by calculating how many shakes of a dice would be equivalent to the spontaneous springing into being of, say, an eye. Since natural selection is very much not a chance process, shaking dice is completely irrelevant.
But the sentence from the Insert uses the word ‘undirected’ as a synonym for random, and this needs more thoughtful handling. Natural selection is certainly not a random process, but is it ‘directed’? No, if directed means guided by deliberate, conscious, intelligent intention. No, if directed means aimed at some future goal or target. But yes, if directed means leading to adaptive improvement; yes, if directed means giving rise to a superficially convincing illusion of brilliant design. For this, natural selection assuredly does. Darwin’s achievement was not to denigrate the elegance of the illusion of design but to explain that it is an illusion.
There are many unanswered questions about the origin of life which are not mentioned in your textbook, including:
• Why did the major groups of animals suddenly appear in the fossil record (known as the ‘Cambrian Explosion’)?
We are extremely lucky to have any fossils at all. After an animal dies, many conditions have to be met if it is to become a fossil, and one or other of these conditions usually is not met. I personally would consider it an honour to be fossilized, but I don’t have much hope of it.
It is particularly difficult for animals without hard skeletons to be fossilized.*3 Therefore, we wouldn’t ordinarily expect to see the soft ancestors of animals that eventually evolved hard skeletons. We’d expect fossils to appear suddenly, when hard skeletons arose.
There are rare, exceptional circumstances in which the soft parts of animals are preserved. One of the outstanding examples is the fossil bed known as the Burgess Shale, in Canada. The Burgess Shale, together with a similar area in China, is the best fossil bed we have from the Cambrian era. What must have happened is that the ancestors of these animals evolved by gradual degrees before the Cambrian era, but didn’t fossilize.
As I said, we are lucky to have any fossils at all. But in any case, it is misleading to think that fossils are the most important evidence for evolution. Even if we had no fossils whatsoever, the evidence for evolution from other sources would still be overwhelmingly strong.
• Why have no new major groups of living things appeared in the fossil record for a long time?
Major groups do not, and should not (according to the Darwinian theory) ‘appear’ in the fossil record. On the contrary, they should gradually evolve from earlier ancestors. Anyone would think that new phyla are supposed to spring spontaneously into existence.*4 Some forms of creationism might have them springing spontaneously into existence, but not Darwinism. The major divisions of the animal kingdom, the phyla, started out, mostly in the Precambrian, as different species.*5 Then they gradually diverged and diverged. A little bit later they became distinct genera. Then distinct families, then distinct orders, and so on. You wouldn’t expect new phyla to ‘arise’ in recent times because by the time we see them they haven’t had time to diverge far
enough away from their ancestors to be recognized as distinct phyla. Come back in five hundred million years and birds, for instance, may have evolved so far from the other vertebrates that they will be classified as belonging in their own phylum.
As an analogy, think of an old oak tree with major boughs bearing small twigs. Every major bough began life as a small twig. If somebody said to you: ‘Isn’t it odd, no new major boughs have sprung from this tree for a long time? All we’ve had in recent years is new small twigs,’ you’d think they were pretty stupid, wouldn’t you? Well, yes, stupid is the word.
• Why do major new groups of plants and animals have no transitional forms in the fossil record?
It is astonishing how frequently this is stated in creationist literature. I don’t know where it came from, because it simply isn’t true. It seems to be sheer wishful thinking. In fact, just about every fossil found is potentially an intermediate between something and something else. There are gaps too, for the reasons I have stated. But what there is not is a single example of a fossil in the wrong place. The great British biologist J. B. S. Haldane was once challenged, by a zealous proponent of Karl Popper’s philosophy that science proceeds by proposing falsifiable hypotheses, to name a single discovery which would falsify the theory of evolution. ‘Fossil rabbits in the Precambrian,’ Haldane growled. No such misplaced fossil has ever been authentically found.
All the fossils that we have are in the right order. Creationists know this and see it as an awkward fact that needs explaining. The best explanation they can come up with is truly bizarre. It all came about because of Noah’s Flood. The animals understandably tried to save their skins by heading for the hills. As the waters rose, the cleverest animals held out longest and reached higher up the slopes before drowning. That’s why we find fossils of ‘higher’ animals above fossils of ‘lower’ animals. Well, ad hoc explanations don’t come more piteously desperate than that.*6
Part of the creationist error about gaps in the fossil record may come from a gleeful misunderstanding of the theory of punctuated equilibrium, propounded by Eldredge and Gould. Eldredge and Gould were talking about a jerkiness in the fossil record, which stems from the fact that, on their view of evolution, most evolutionary change takes place relatively rapidly, during what they call speciation events. Between speciation events there are long periods of stasis during which no evolutionary change occurs. It is a ludicrous confusion to muddle this up – as creationists wilfully do – with major gaps in the fossil record such as that which preceded the so-called Cambrian Explosion. I have already quoted Dr Gould’s justified annoyance at being persistently misquoted by creationists.
Finally, there is a purely semantic point about classification. I can explain it best with an analogy. Children turn gradually and continuously into adults but, for legal purposes, the age of majority is taken to be a particular birthday, often the eighteenth. It would therefore be possible to say: ‘There are fifty-five million people in Britain but not a single one of them is intermediate between non-voter and voter. There are no intermediates: an embarrassing gap in the developmental progression.’ Just as, for legal purposes, a juvenile changes into a voter as midnight strikes on their eighteenth birthday, so zoologists always insist on classifying a specimen as in one species or another. If a specimen is intermediate in actual form (as many are, in accordance with Darwinian expectations), zoologists’ legalistic conventions still force them to jump one way or the other. Therefore the creationist’s claim that there are no intermediates has to be true by definition at the species level, but it has no implications about the real world – only implications about zoologists’ naming conventions.
The proper way to look for intermediates is to forget the naming of fossils and look, instead, at their actual shape and size. When you do that, you find that the fossil record abounds in beautifully gradual transitions, although there are some gaps too – some very large and accepted, by everybody, as due to animals simply failing to fossilize. To look no further than our own ancestry, the transition from Australopithecus to Homo habilis to Homo erectus to ‘archaic Homo sapiens’ to ‘modern Homo sapiens’ is so smoothly gradual that fossil experts are continually squabbling about where to classify – how to name – particular fossils. Now look at the following, from a book of anti-evolution propaganda: ‘The finds have been referred to as either Australopithecus and hence are apes, or Homo and hence are human. Despite more than a century of energetic excavation and intense debate the glass case reserved for mankind’s hypothetical ancestor remains empty. The missing link is still missing.’ One is left wondering what a fossil has to do to qualify as an intermediate. What could it conceivably do? In fact the statement quoted is saying nothing whatever about the real world.
• How did you and all living things come to possess such a complete and complex set of ‘instructions’ for building a living body?
The set of instructions is our DNA. We got it from our parents, and they got it from their parents, and so on back to a tiny, remote ancestor, simpler than a bacterium, which lived about four thousand million years ago in the sea.
Since all organisms inherit all their genes from their ancestors, rather than from their ancestors’ unsuccessful contemporaries, all organisms tend to possess successful genes. They have what it takes to become ancestors – and that means to survive and reproduce. This is why organisms tend to inherit genes with a propensity to build a well-designed machine: a body which actively works as if it is striving to become an ancestor. That is why birds are so good at flying, fish so good at swimming, monkeys so good at climbing, viruses so good at spreading. That is why we love life and love sex and love children. It is because we all, without a single exception, inherit all our genes from an unbroken line of successful ancestors. The world becomes full of organisms that have what it takes to become ancestors.
There’s a lot more to it than that. Evolutionary arms races, such as the race run in evolutionary time between predators and their prey, or parasites and their hosts, have led to escalating perfection and complexity. As predators become better equipped to catch prey, so prey have become better equipped to evade capture. This is why antelopes and cheetahs both run so fast. It is why they are so good at detecting each other’s presence. Many details of a cheetah’s or an antelope’s body can be understood if you realize that each is the end product of a long evolutionary arms race against the other.
Study hard and keep an open mind. Someday, you may contribute to the theories of how living things appeared on Earth.
Well, at last I’ve found something I can agree with.
* * *
*1 The only exception might be a respectable scientist such as Paul Davies (see this page) who acknowledges the faint possibility that life may have arisen more than once, and that survivors, recognizable by their different genetic code, may still be among us. This conceivable exception in no way changes my statement. Purists could amend it to ‘All known animals, plants…’
*2 More to the point, if the sun had behaved in the way described by seventy thousand eye-witnesses in Fatima, our planet, if not the entire solar system, would have been destroyed. Eye-witness testimony is not all it’s cracked up to be – a fact, incidentally, that trial juries need to understand better.
*3 The turbellarian flatworms are a large, beautiful and flourishing class of animals. There are about as many species of Turbellaria as there are mammals, yet not a single turbellarian fossil has ever been found. Creationists presumably believe the Turbellaria have lived on Earth for the same length of time as all other animals, give or take a day or two during October 4004 BC. So if a massive class of animals failed to leave a single fossil, surely the vertebrates can be forgiven for a few ‘gaps’ in their fossil record.
*4 This was exactly the misapprehension formed by the distinguished (and far from stupid) theoretical biologist Stuart Kauffman, who imagined that ‘species which founded taxa appear to have built up the higher taxa from the top down. That is,
exemplars of major phyla were present first, followed by progressive filling in at class, order, and lower taxonomic levels.’ This profound misunderstanding was nurtured by the excesses of ‘poetic science’ beloved of Stephen Jay Gould – specifically, Gould’s book Wonderful Life – against which I warned in the Afterword to the essay on ‘Universal Darwinism’ in section II of this collection.
*5 It is surprising but true. Even more surprising, before they became separate species, the ancestors of any two of today’s phyla were once offspring of the same mother. Take a human and a snail, for example. If you trace our ancestors back sufficiently far, and trace the snail’s ancestors back sufficiently far, you will eventually converge on a single individual, the common ancestor of them both. One child of this parent was destined to give rise to us (and all the vertebrates plus starfish and some worms). Another child of this parent was destined to give rise to snails (and insects, most worms, lobsters, octopuses etc.).
*6 Even a member of the Alabama State Legislature might be capable of understanding that an explanation of that kind can, in any case, only ever be statistical, not absolute. The ‘head for the hills’ theory might explain why there is a statistical preponderance of advanced animals in higher strata. But the trend could only be statistical. In actual fact, there is not a single exception to the rule, not one single solitary example of a mammal fossil, say, in a stratum too low in the fossil record.
The guided missiles of 9/11*
A CONVENTIONAL GUIDED MISSILE corrects its trajectory as it flies, homing in, say, on the heat of a jet plane’s exhaust. A great improvement on a simple ballistic shell, it still cannot distinguish particular targets. It could not zero in on a designated New York skyscraper if launched from as far away as Boston.
Science in the Soul Page 24
