Thursday, April 17, 2008
DARWIN, CREATIONISM AND EVIDENCE
Here's something I have been working on. Comments please. It needs a final para. Warning - about 3.5k words!
DARWIN, CREATIONISM AND EVIDENCE
Both the general theory of evolution and Darwin’s particular theory of evolution by natural selection are regularly challenged by people who describe themselves as “creationists”. There are several varieties of creationism. The focus here is on what is often called “young earth creationism”: the view that the entire universe is approximately six thousand (certainly less than ten) thousand years old, and that all living species were created within the first few days of creation. Henceforth, when I speak of “creationism”, it is young earth creationism I have in mind.
Why would anyone believe creationism? Typically, because they are Bible literalists. Creationists believe that Genesis provides an historically accurate account of origin of the universe and life. Their chronology is based primarily on the number and ages of the generations listed in the Old Testament.
Belief in creationism isn’t confined to a few religious cranks. Recent polls fairly consistently indicate that, currently, about one third to one half of all U.S. citizens are creationists. Nor is creationism solely the preserve of the unintelligent or ill-educated. It seems that significant numbers of college graduates are drawn to Bible literalism. A Tennessee academic who surveyed his own students a few years ago found that about a third were creationists. He complained that scientists like himself are having to fight
the battles of the Enlightenment all over again. Medieval ideas that were killed stone dead by the rise of science three to four hundred years ago are not merely twitching; they are alive and well in our schools, colleges and universities.
These medieval ideas are also taking root outside the U.S. Because of the evangelism of American Bible-literalists, creationism is on the rise around the world. Russia and Eastern Europe, in particular, are heavily targeted by Christian fundamentalists for whom states newly liberated from communism promise a new frontier in their project to spread creationist ideas around the world. In 2004, the Serbian education minister Ljiljana Colic succeeded (if only temporarily) in removing the teaching of evolution from all state schools, replacing it with the teaching of young-Earth creationism instead. Creationism is widespread in many African states, and also among those many Muslims for whom the literal truth of the Old Testament is also an article of faith.
For most creationists, the literal truth of the Old Testament is a “faith position”. They insist they would maintain their belief even if the scientific evidence seemed conclusively to falsify it.
Nevertheless, many creationists believe that their theory is scientifically respectable. It is, they suppose, supported by the available empirical evidence. Indeed, creationism has its own research centres – including the Institute for Creation Research – as well as its own conferences, publications and PhD-qualified researchers.
It is the claim that creationism is a scientifically robust theory at least as empirically well-supported as its rivals that I shall focus on here. How, exactly, do creationists convince themselves of the scientific validity of their theory?
The fossil record
Let’s begin with an illustration: creationist attempts to deal with the fossil record. Examination of the rock beneath our feet reveals strata that have been laid down, apparently over many millions of years. Fossils can be found embedded in these strata. And we find different life-forms fossilized in different levels. At the lowest levels, only very simple creatures are found. Higher up we discover more complex forms, including the dinosaurs. Higher still we find mammals. Only the most recently deposited layers reveal traces of man.
This layering of the fossil record tallies well with the theory of evolution, but seems to contradict the Biblical account on which all life-forms were produced more or less simultaneously about six thousand years ago. If the Biblical account were correct, we should presumably expect to find examples of the entire range of life-forms fairly randomly distributed throughout the strata (assuming, that is, that the few thousand years that have elapsed since creation would suffice to allow such rock strata even to form).
According to creationism, for example, man and all the other mammals walked the Earth at the same time as the dinosaurs. So shouldn’t we expect to find fossils of both man and all the other mammalian species muddled up in the same layers as dinosaur fossils? Yet we find distinct layering, with, for example, the larger mammals only ever appearing in the higher strata. Such evidence seems to count fairly decisively against creationism.
While the fossil record might seem to provide powerful evidence against creationism, creationists argue that the situation is not so simple. Indeed, they have shown some ingenuity in their attempts to explain how their theory also fits the available data.
Creationists maintain that the layering in the fossil record can be explained by reference to the Biblical Flood (the one on which Noah famously floated his ark). The rains that caused the Flood were responsible for producing huge mud deposits that then metamorphosed into the rock strata we find beneath our feet. Creationists insist that the ordering of the life-forms within these layers can also be accounted for on their theory. For example, some have suggested the reason we find dinosaurs below larger mammals is that dinosaurs are slow, cumbersome, comparatively unintelligent creatures that are likely to have been buried before the faster and more intelligent larger mammals that would have run to higher ground. Nor, as the Christian website www.christiananswers.net attempts here to explain, should we expect to find fossils of humans in the lower sedimentary layers. The layering we find in the fossil record
can be more reasonably explained by Flood geologists as due to the order of burial of the different ecological zones of organisms by the Flood waters. For example, shallow marine organisms/ecological zones would be first destroyed by the fountains of the great deep breaking open, with the erosional runoff from the land due to torrential rainfall concurrently burying them. On this basis we would probably not expect to find human remains in the early Flood strata, which would contain only shallow marine organisms. The fossil record as we understand it at the moment certainly fits with this.
We have here an example of a standard creationist manoeuvre: by adapting and developing their own core creationist theory in various ways, evidence that might seem straightforwardly to falsify their theory is shown, with varying degrees of ingenuity, to “fit” with creationism after all.
Similar moves are made to deal with other evidence. Take the light arriving here from distant stars. That light would in many cases have had to travel for much longer than six thousand years to arrive here. It seems, then, that the universe must be much older than six thousand years. One creationist response to this evidence is to develop a theory on which the speed of light is actually slowing down. Technical papers filled with equations have been published in support of such rival creationist theories.
Or take the slow movement of tectonic plates to produce mountain ranges and the slow process of erosion to shape them – surely a range such as the Himalayas – is powerful evidence that these processes have been in operation for millions of years, not just a few thousand?
In response, creationists have suggested that tectonic plates can and have moved much more rapidly than they do at present, and that erosion can also take place very quickly under conditions such as those that occurred during the flood (a claim which, they suppose, also accounts for structures such as the Grand Canyon).
Now, if your conception of good scientific practice is simply to develop theories in such a way that they become consistent with the available empirical evidence, then it might strike you that what creationists are practising here is, indeed, good science. They even have a “research program” of sorts: to refine and shape their core theory in such a way that it comes to fit the evidence.
What creationist scientists practice certainly looks to many like solid, respectable science. Indeed, many millions of American citizens, many of whom are intelligent, college-educated people, believe that creationism is good science. Have all these people been duped? Or is so-called “creation science” good science after all.
Whether or not creation science even qualifies as science (and I have my doubts) it certainly isn’t good science. In order to see why, we need to develop a slightly more sophisticated understanding of what good evidence is.
I am going to focus in turn on the two ways evidence can be applied – as evidence against, or for a theory.
Are dogs Venusian spies?: dealing with evidence against your theory
Suppose that, for some strange reason, I come to believe that dogs are spies from the planet Venus. Amazed I could believe anything so foolish, you proceed to wheel out counter-evidence. “But dogs can’t even speak!” you point out. My reply: “They can speak, but simply choose to hide this ability from us.” “But they have no method of communicating with Venus”, you add. I reply: “Ah, they communicate by means of secret radio transmitters.” “But we have searched everywhere, and can find no evidence of such transmitters.” I reply: “The transmitters are embedded in the brains.” “But we have X-rayed their heads, and can find no transmitters!” I reply: “The transmitters are made of an organic material indistinguishable from brain stuff.” “But we can detect no signals coming from dogs’ heads.” “The signals are sent via a medium that we are, as yet, unable to detect.” “But Venus is a lifeless, uninhabitable planet.” “The Venusians live in deep underground bunkers where they are protected from the harsh atmosphere.” And so on. You can see that, with a little ingenuity, I might continue to play this game forever. Yes, there is a mountain of evidence that dogs are not Venusian spies. And yet, for any piece of evidence you might care to wheel out, it is always possible for me to concoct some explanation for that evidence – an explanation on which my theory that dogs are Venusian spies is consistent with that evidence.
Yet, clearly, despite the fact that I can continue to make my theory fit the evidence in this way, my theory is patently ridiculous. Certainly, what I am practising is not good science.
The moral is that, whatever good scientific practice is, it requires rather more than that we simply busy ourselves constructing theories that are consistent with the available evidence.
Any theory, no matter how ludicrous, can be made consistent with the available evidence, given enough ingenuity.
Yet the approach of “creationist scientists” is, to a very large extent, similar. Orthodox scientists who attempt quickly to dismiss creationism by wheeling out evidence that seems straightforwardly to falsify it often find themselves tied up in knots by opponents, who, armed with an array of moves developed by the Institute for Creation Research, etc., are able to show how creationism really does fit the evidence after all.
There’s a further moral we can draw. We can now see that, in order for evidence strongly to confirm a theory, more is required than that the theory be consistent with the evidence. Creationist understanding of good science seems often to involve a muddling of this distinction between evidence being consistent with a theory and evidence supporting a theory.
I have drawn a parallel between the strategy I adopted to defend my belief that dogs are Venusian spies, and the strategy adopted by creationists to deal with seeming counter-evidence to their theory. But we do need to add a caveat here. The caveat is that, actually, even reputable scientists do make these kind of moves on occasion.
Here’s an example. When the heliocentric model of the universe was proposed, objectors pointed out what seemed to be powerful evidence against the theory. If the Earth were travelling round the sun, then the fixed stars should appear to wobble back and forth across our cosmic field of view over the course of a year (in much the same way that, if I walk around a lamp post while looking due north, the houses across the street should move back and forth across my field of view). The absence of any such observable parallax was an embarrassment for the new theory, and it prompted the response that the stars must, therefore be at a much greater distance than had previously been thought, making the parallax effect so small as to be undetectable. This explanation, it later turned out, was correct, though there was no way that those who originally made it could establish this at the time.
We have here an example of reputable scientists explaining away seemingly contrary evidence in much the same way creationists explain away the evidence against their theory. This is by no means a rare occurrence in scientific circles. And why not? Surely it’s not always unreasonable to defend a theory by constructing such alternative explanations for apparent counter-evidence? But then why shouldn’t creationists adopt the same strategy?
Because, while this strategy can be reasonable, clearly there are limits. Certainly, the strategy may well be reasonable if, say, the theory is otherwise well confirmed, the contrary evidence is limited, and if the alternative explanations have further independently-testable consequences. But clearly, my defence of the theory that dogs are Venusian spies fails on at least two of these three counts. Not only is my theory is not strongly confirmed (see below), it faces so much contrary evidence that my strategy of seeking to explaining away that evidence becomes ridiculous. I end up having to devote almost all my intellectual energy to constructing ever-more elaborate explanations of why the evidence is, after all, consistent with my belief that dogs are Venusian spies.
Creationism shares both these failings. Not only is their core theory not strongly confirmed (as I will further explain shortly), much of the intellectual effort of “creation scientists” is inevitably focussed on their programme of coming up with explanations to show how seemingly contrary evidence is consistent with their theory after all.
What creationists practice might look a bit like science to the untrained eye. After all, it's true that they are using imagination and ingenuity to develop a theory that continues to fit the available evidence. But, because the spend so much of their energy attempting to explain away counter-evidence, their method is essentially unscientific.
Reasoning of the insane
We have seen that, in defending the theory that dogs are Venusian spies, my method may resemble the scientific method in certain respects, but differs essentially from it. Indeed, were I to continue to defend my dogs-are-Venusian-spies theory in this manner, not only would I start to infuriate my audience, I would quite properly be suspected of suffering from some sort of mental illness.
Indeed, in its most extreme form, this pattern of thinking – the strategy of explaining away counter-evidence ad nauseum - surely is characteristic of certain forms of insanity. Anyone who has spent some time in the company of someone who, perhaps because of a serious psychiatric condition, is severely deluded will recognize the frustration of trying to convince them of the error of their ways, when they can apply their often considerable ingenuity to developing ever-more elaborate explanations to deal with your evidence that, whatever they might think, dogs really aren’t Venusian spies.
Of course, creationists aren’t (usually) mentally ill, but it’s striking how their thinking often exhibits this same peculiar pattern of thought – a pattern that allows them effectively to seal themselves off inside a their own bizarre bubble of belief.
When does evidence strongly support a theory?
Let’s now look at how evidence can be used to support a theory. Evidence can support a theory to varying degrees, of course. An observation of a single white swan is some evidence that all swans are white. But not very much. Observe more white swans and no black ones, and the degree of evidential support increases somewhat.
Under what circumstances is a theory strongly confirmed by a piece of evidence? That’s to say, under what conditions does a piece of evidence, while perhaps not by itself sufficient to make it rational to believe the theory, nevertheless very significantly support it? It seems three things are required.
o First, the theory must allow us to deduce observational consequences: consequences that can be clearly and precisely stated.
o Second, there should be a sense in which the prediction is surprising and unexpected.
o Third, the prediction should turn out to be true.
The first two conditions explain why, for example, the kind of predictions made by end-of-pier astrologers and psychics rarely constitute strong evidence in support of the claim that the have genuine occult powers.
Note, first, that such predictions as that I will soon meet a dark and handsome stranger, or will come into a sum of money, or know someone with health problems, are obviously pretty vague – does “soon” mean this week, this month or this year? How much money is a “sum”, what counts as “dark”? Does the common cold count as “health problems”? This vagueness makes it far easier for the astrologer or psychic to insist that their predictions have come true.
But in fact, even without the very considerable wiggle room provided by such vagueness, these predictions may well come true anyway. Most people know someone with health problem, will soon meet a dark stranger, and will come into some money in the not too distant future. These predictions are unsurprising in this sense: that they are likely to be true anyway, irrespective of whether the hypothesis that the psychic or astrologer has genuine powers is true. In which case, the discovery that they are true provides very little evidence in support of that hypothesis.
Contrast the above “evidence” for genuine occult powers with, say, some of the evidence in support of the theory of evolution (whether or not it be Darwin’s version). From the hypothesis that all species have evolved over millions of years by increments from some common ancestor, we can derive, for example, this observational consequence: that the fossil record will be contiguous and progressive. The theory predicts that the fossils will line up in a very specific manner: a manner consistent with the claim that later species evolved from the earlier. It predicts we won’t find any out of order fossils (e.g. we won’t dig up cow fossils in the pre-Cambrian layers). It also predicts that we will discover fossils of extinct species that are morphologically transitional between existing species. The theory predicts a great may other things too, of course, but if we focus on the prediction about no out of order fossils, notice that it does met our three requirements for strong confirmation. The prediction of a contiguous and progressive fossil record is pretty clear and precise. It is also surprising in the sense we require for strong confirmation – if the theory were not true, then there would be no particular reason to expect the fossils to line up in such a precise manner. And yet, even after we have dug up millions of fossils, including many thousands of mammal and dinosaur fossils, there has not been even a single well-documented instance of an out of place fossil. If the theory were not true, the fact that there has not been even one such fossil would be a quite extraordinary coincidence. So the fact that the fossils do line up in this very particular way very strongly confirms the theory.
In response, a creationist might insist that the fact that the fossils do line up in this manner is not particularly unexpected on their alternative theory. Certainly, we have seen that they tell a story about the biblical flood that makes the actual arrangement of fossils consistent with their theory. But is, not just a rough banding of dinosaurs and humans into different layers, but this very particular kind of ordering throughout the layers predicted by the theory of evolution, something which, even according to creationism, is not unlikely? Surely not. Even if creationism can be made consistent with the fossil record, it certainly doesn’t give a particularly high probability to this very specific arrangement of fossils. So, as a prediction, it is, in the relevant sense, surprising. But then, as the prediction is also true, the theory of evolution is strongly confirmed.
What about creationism? Is that also strongly confirmed by, say, the fossil record? No. For creationism doesn’t make any clear, precise and surprising predictions regarding what we should expect to dig up. Creationism doesn’t really make any particular clear, precise and surprising predictions about what we should expect to dig up. Whatever we dig up, they can say – “Hey: that’s just what we expected!”
In short, to be strongly confirmed, a theory has, as it were, to really stick its neck out with regard to predictions – to take very significant risks so far as being proved wrong is concerned. The theory of evolution takes such risks with the fossil record, which is why it can be strongly confirmed by it. Creationism does not.
That the theory of evolution sticks its neck out so far as the fossil record is concerned, whereas creationism does not, is indeed, acknowledged in this quote from the creationist website www.answersingenesis.com:
If human and dinosaur bones are ever found in the same layers, it would be a fascinating find to both creationists and evolutionists. Those who hold a biblical view of history wouldn’t be surprised … Evolutionists, on the other hand, who believe the geologic layers represent millions of years of time, would have a real challenge. In the old-earth view, man isn’t supposed to be the same age as dinosaurs…. As biblical creationists, we don’t require that human and dinosaur fossils be found in the same layers. Whether they are found or not, does not affect the biblical view of history.
What these creationists fail to realize, however, is that it is precisely their lack of commitment one way or the other so far as how human and dinosaur fossils should be arranged that gives the theory of evolution a very significant advantage over their own. For, unlike their own theory, the theory of evolution can then be strongly confirmed by what is dug up.
I have been looking at the general strategy of creationists regarding evidence. We have seen that, to some extent, their strategy does resemble the scientific method. Indeed, it resembles it enough to fool many people into thinking that creationism is “good science”. However, we have also seen that, (i) unlike genuinely good scientific theories such as the theory of evolution (and also Darwin’s version of it), creation science expends far too much of its intellectual energy trying to explain away enormous amounts of counter-evidence, and (ii) it also (as I have at least illustrated, if not yet established) takes few risks with the empirical evidence, with the consequence that, unlike the theory of evolution (and Darwin’s version of it), it cannot be strongly confirmed by that evidence.
Evidence against evolution/ for creationism
I have not yet included everything that gets done under the banner of creation science. For example, creation scientists also spend much energy cataloguing what they consider to be evidence against Darwin’s theory, the theory of evolution more generally, and of course the theory that the universe is far older than just a few thousand years. Because every scientific theory, no matter how successful, has its problems to deal with, it’s not difficult for creation scientists to find and then widely publicize such via the internet, church meetings and events, and so on, in such a way as to give audiences the impression that, while creationism may have its problems, so do its rivals. So don’t both deserve to be taken seriously?
What such creationists presentations obscure, of course, is the sheer scale of the problems facing creationism compared to those facing the theory of evolution, etc. But in any case, many of the “problems” that the theory of evolution supposedly faces aren’t really problems at all.
Here’s just one example of such a pseudo-problem. Attend a public lecture by a creationist are you may be shown dramatic slides of fossils which, its claimed, disprove the theory of evolution. Take, for example, images of trees fossilized upright through rock strata (there are some famous examples at Yellowstone park, U.S.A.). Such polystrate fossils (see illustration above), say some creationists, are powerful evidence that these trees were buried quickly, as their creationist Flood theory predicts, not slowly over millions of years, as the theory of evolution demands (if the process were that slow, the creationists point out, then the tree would have long rotted away before any higher sedimentary layers were added). While such dramatic images and arguments may persuade some audiences, the truth is that polystrate fossils are no problem at all for the theory of evolution. The theory acknowledges that sedimentary layers are sometimes rapidly laid down (besides rivers, for example, or during a rapid series of volcanic eruptions). So, on the theory of evolution, polystrate fossils are to be expected. Evangelical creationists who present such images in such a misleading way are either woefully ignorant about fossils, or else are else are guilty of deliberately misleading their audiences. Such pseudo-problems abound in creationist media.