The Greatest Show On Earth by Richard Dawkins: CHAPTER 4 'Silence and Slow Time'
The evidence is in the layers!
As a creationist, I guess I would be accused of selectiveness if I ignored this chapter, as this is the one which RD claims that YEC are ‘deluded’.
I am not trying to use this review, to put forward my religious beliefs, but to examine the ‘evidence’ that RD puts forward, and in my opinion, this is the first chapter in which he actually presents what he calls ‘evidence’.
The view that RD wants us to believe is that there is only one way to interpret the evidence, but rather than try to promote the view which I personally subscribe to, I intend to offer ‘an’ alternative view to that of RD, and to demonstrate that far from the evidence constraining us to a single view, it is our interpretation of the evidence, rather than the data itself, which leads us to accept or reject the views held by other people. As RD has said, we ‘believe’ it because it fits in with our worldview’
I have my views, he has his, but in this review, I am seeking not to compare our wider points of view, by comparing atheist / Christian, but simply presenting, examining and commenting upon the ‘scientific evidence’ RD gives us in this book.
So, with this in mind, let’s get to his opening sentence of the chapter.
“If the history-deniers who doubt the fact of evolution are ignorant of biology, those who think the world began less than ten thousand years ago are worse than ignorant, they are deluded to the point of perversity. They are denying not only the facts of biology but those of physics, geology, cosmology, archaeology, history and chemistry as well.” P85
These are strong words from RD, and as you would expect, they will be quoted often, as they put across his point of view of creationist pretty succinctly, and cause enough controversy to gain publicity for the book. I guess that it is besides the point that the statement is, to say the least, inaccurate. To start with there are many creationists that are very highly qualified biologists, that doubt that evolution is a ‘fact’ so they can hardly be accused of being ignorant. Likewise there are a great number of highly qualified physicists, geologists, cosmologists, archaeologists, historians and chemists, that not only “doubt the fact of evolution”, but also believe that the Earth is less than 10,00 years old, so it is not due to ignorance, but for other reasons that they do so. He of course makes the statement they are denying “facts”, but this too, is not accurate.
He does not list a single “fact” that they deny, but as usual he makes the assertion, and fails to back it up with any evidence. Creationists do not deny “facts”, they deny the interpretation of some “facts”.
Let me illustrate. It is a fact that ‘Grand Canyon’ is over 4 miles wide and about 6000 feet deep, at some points. http://en.wikipedia.org/wiki/Grand_Canyon
It is NOT a FACT that “The canyon was created by the Colorado river over a 5.4 million year period.” This is an INTERPRETATION of the fact that Grand Canyon is there.
It is a FACT that most of the Earth is covered with layers of sedimentary rock; it is NOT a FACT that these layers were laid down over millions of years, this is an INTERPRETATION of the presence of these layers.
So whilst RD wants you to believe that creationist deny FACTS, he is wrong, and he does not name one FACT in any of these various disciplines that he mentions. Time and again in this book, RD fails to back up his statements but simply makes assertions and expects us to take his word for it.
So, once again, creationists do not deny facts, they dispute the INTERPRETATION placed on some observations and the validity of some experimental results, but we will get to these later. Let us move on with the chapter. RD tells us;
“The ‘time of death’ is a baseline fact, an inerrant pivot around which more or less far fetched speculations by the detective revolve...The clocks available to the evolutionary scientist are potentially more accurate...” p85
In this chapter then, RD shows us what ‘clocks’ and timescales are used for evolutionary biology.
What are the ‘clocks’ that he uses, and how reliable are they?
The first clock he uses are tree rings, which he says are accurate to one year, but he admits that the furthest this clock can take us back is to 11500 years ago. Of course, he does not quote a source for this ‘piece of information’, but my guess is that he simply states it, as if by this one method alone he can prove that YEC are wrong.
Moving on to ‘Radioactive clocks’, he acknowledges that creationists accept the atomic theory, which he goes on to describe pretty well.
“The predictability of the rate of decay is the key of all radiometric clocks”p94
“Every unstable or radioactive isotope decays at its own characteristic rate which is precisely known.”p95
We shall explore how “precisely known” these rates are, and I will contend they are not as certain as RD will have you believe.
He points out that the ‘half-lives’ of some elements are 49 BILLION years (indeed one isotope SE-82 has a half-life of 1.3*1020 years which expands out to 130,000,000,000,000,000,000 years or simply 130 quintillion years. http://en.wikipedia.org/wiki/Selenium
Although I do not doubt that it is possible to measure the ‘theoretical’ decay of an element and calculate the half life to this timescale, but, as this requires us to extrapolate far beyond, even the most ardent evolutionists greatest estimate of the age of the universe, it can hardly be said to be anything more than a ‘theoretical possibility’ If you want to believe that they can know these rates of decay ‘precisely’, you have a lot more faith than I do! When rates of decay are so far in excess of the ‘supposed’ known age of the universe, I have to doubt what is meant by ‘precisely known’. This is a huge claim, even for RD!
The potassium/ argon clock.
“An isotope much used on the evolutionary timescale is potassium 40 with a half-life of 1.26 billion years…IMAGINE that you start with some quantity of potassium 40 in an enclosed space with no argon 40…years have elapsed, a scientist comes upon the same enclosed space and measures the relative proportions of potassium 40 and argon 40…ASSUMING there was no argon to begin with one can estimate the time that has elapsed…Notice that we must know the ratio of parent (potassium-40) to daughter (argon-40) isotopes. Moreover…it is necessary that our clock is zeroed.”p96 (some large snips and emphasis added.)
In this passage, RD has given a fair and accurate account of how these clocks are ‘supposed’ to work. I will contend that there are several problems with this, which lead to ‘uncertainties’ which call the results into question.
First of all, I am not convinced that they can ‘know’ precisely the decay rate of 1.26 BILLION years Knowing suggests a degree of certainty, and my contention is that it is only possible to ‘estimate’ time scales in millions or billions of years, as there is no way to verify them indepentantly.
How long did they measure it for? And how certain can they be, since even if they started 100 years ago measuring it, (which as far as I know they did not) they may not have a ‘precise’ rate of decay, and if this is not right, which RD acknowledges ‘is the key’ then any ages based on it are faulty.
RD statement of the certainty of the rate is called into question by another quote that he makes in a later chapter, far away from this discussion, but it is relevant so I will quote it now.
“Neither radioactive clocks nor molecular clocks tick in a regular fashion like a pendulum clock or a watch. If you could hear them ticking, they sound like a Geiger counter…A Geiger counter doesn’t tick regularly, the ticks coming in strange stutter bursts.” p336
So even he knows that the ‘ticks’ are not regular, and therefore even listening to the ticks for a long time, you could not be sure that you could work out the ‘precise’ rate, as you would not know if you were listening to the correct rate of ‘stutter bursts’. So, I would suggest, there is room for a ‘reasonable doubt’ about using this ‘dating method’.
Next, as he is keen to have us do, he wants us to IMAGINE starting with a known amount of potassium in an enclosed space. This is not realistic, as the rocks which are dated by this method, are NOT in an enclosed space, and therefore we cannot rule out the possibility of any contamination from another source, or leakage form the rock either. So this creates another area of ‘uncertainty’.
Another ASSUMPTION that is made is that the rocks were ‘zeroed’ and that there was no argon present to start with. This is an assumption that may or may not be true, but the fact that it is not known for certain, creates another area of ‘uncertainty’. So, rather than this clearing up the matter of the dating of things by this method, I feel there is sufficient ‘uncertainties’ to leave a reasonable doubt. But, I do not want to focus on this point, as I do not feel that he can show that even allowing for the long ages that he needs, that he can prove beyond a reasonable doubt the ‘fact’ of common ancestry, and therefore I will assume that the clocks are ‘reasonably accurate’ and move forward allowing their ‘testimony’.
“Like all the radioactive clocks used by geologists, potassium/argon timing works only with so-called igneous rocks...Only igneous rock provide radioactive clocks, but fossils are almost never found in igneous rock. Fossils are formed in sedimentary rocks like limestone and sandstone...They are layers of mud or silt or sand, gradually laid down on the floor of a sea or a lake or estuary.” P96, 97
As we can see, radioactive clocks are not used to date fossils directly, so when we hear that a fossil has been dated to be so many millions of years old, it has not been dated by radioactive clocks, but by using several ASSUMPTIONS which may or may not be true.
“So, from a timekeeping point of view, sedimentary rock is a mess. It can’t be used. The best we can do - and it is a pretty good best – is to use the dates of the igneous rocks that are found near sedimentary rock, or embedded in it.” p98
Here, we are told, that the dating of the layers of sedimentary rock is worked out by dating igneous rock near them.
“Geologists have long known the order in which these named sediments were laid down. It is just that before the advent of radioactive clocks we didn’t know when they were laid down. We could arrange them in order because – obviously – older sediments tend to lie beneath younger sediments.”p98
“Because the relative ordering of the named sedimentary strata is well know, and the same order is found all over the world, we can use igneous rocks that overlie or underlie sedimentary strata, or are embedded in them to date those name sedimentary strata and hence the fossils within them.” P101
So, if I summarize this up to now, RD he telling us that fossils are found almost exclusively in sedimentary rocks, which are silts and mud etc. –laid down by water at the bottom of lakes and seas etc, These sedimentary rocks even cover the top of Mt Everest, showing that at one time, the land which is now the highest point on Earth was once covered by water. It is in this sedimentary rock that we find fossils, these are the remains of organisms that have died and been buried in the sediment, and by dating these layers we have an idea how long ago these creatures died.
“The named strata are usually identified by the fossils they contain. And we are going to use the ordering of the fossils as evidence for evolution! Is that in danger of turning into a circular argument? Certainly not. Think about it. Cambrian fossils are a characteristic assemblage, unmistakably recognizable as Cambrian...A characteristic list of fossils is used to recognize Ordovician rocks, Devonian rocks, and so on. So far all we are using these fossil assemblages for is to identify whether a slab of rock is, say, Permian or Silurian.” p98
RD is giving a lovely summary of how the layers are shown to date the fossils.
There are problems with this method too, as it requires additional assumptions, but as RD does not go into to much detail, I will leave it for another occasion. What he is showing us here though is that the layers are not dated by radiometric dating methods, but by what he calls “indicator species”, but they are mostly known as ‘index fossils’.
Index fossils are particular organisms which are thought to have existed for a known period of time, but are now extinct. They are used to date the layers. So we use fossils to identify the layers, and layers to date the fossils. RD knows that this is circular reasoning, and tries to dismiss it by simply saying, ‘certainly not’. But no matter how quickly he wants to try to dismiss this, this is exactly what is going on.
How old is this fossil? Where did you find it? I found it in such and such a place. Oh, that is a Devonian layer. Your fossil is therefore 360 million years old. How do you know that the Devonian layer is 360 million years old? That is easy, we have what you call ‘index fossils’ they tell us how old the layer is. Well, how do you know that they are 360 million years old? That is easy, because they are only found in the Devonian layer, which is 360 million years old!
It appears that they date the fossils by the layers, and identify the layers by the fossils!
That sounds pretty circular to me.
They also have to work on the ASSUMPTION that these layers are laid down very slowly over millions of years. This is only an assumption, but it does not seem to be reasonable. Can we honestly believe that something as big (or thick) as a large dinosaur could lie undisturbed without decaying, while it is slowly covered over millions of years by sediment?
Indeed some geologists now acknowledge that the Earth has gone through long periods of inactivity, with little or no sediment building up, followed by sudden catastrophes which can lay down very thick layers comparatively quickly. RD does not go too deeply into this, and perhaps we could examine the evidence at a later time, maybe in a review of the book RD recommends “Evolution-what the fossils say”. As for this book, I will go along with his dates and see how far we can get with this. He claims he is going to show us, ‘indisputable evidence for evolution from a common ancestor, which is better than any ‘eyewitness testimony’ ever, so we will go along with his dates for now.
Speaking of the fossils RD states;
“Do they progress in a sensible direction? Do certain kinds of fossils, for example mammals, appear only after a given date, never before? The answer to all such questions is yes. Always yes. No exceptions. That is powerful evidence for evolution.”p99, 100
Yee ha! Finally, on page 100 RD tells us of his first ‘evidence’ of evolution from a common ancestor.
The sequence of layers, dated by the fossils, show that mammals etc, only appear, in a sequence that matches the evolutionary viewpoint. There are no exceptions – none.
There are actually places where so called older rock is on top of so called younger rocks, and it is necessary to offer explanations, for these places, but for now we shall go along with RD to see what evidence he offers.
If we ignore all the assumptions we have to make, to date the fossils, and allow his dates given to the layers, can he provide us with more evidence that the fossil record supports his viewpoint?
We will have to wait until chapter 6 for that discussion, but he does tell us here:
“Evolution, in other words, is a falsifiable and therefore scientific theory.”
I am sure that most of us have heard this before. I wonder how many more times I will be asked to show just one rabbit in a Cambrian layer.
RD then quotes from a ‘prizewinning creationist site’. Is it Answers in Genesis, or ICR, no it is http://homepage.ntlworld.com/malcombowden/creat.htm He does not tell you this of course in the main text, you have to go the notes at the back of the book to discover, which ‘prizewinning creationist site’ he is talking about. By the way, it did not work for me, so whilst I don’t doubt that it was there, I cannot access it now to confirm his claim.
He calls the theory which was apparently on this site, the “head for the hills” theory. Rather than giving this ‘theory’ his normal thrashing, he simply comments, this theory “would predict a statistical tailing off”. Has RD gone soft on the creationist, why is his reply so mild mannered and matter of fact. I don’t know.
On page 102 we are shown a table with the half-lives of various unstable isotopes, which range from 49 billion years to about 6000 for carbon 14. He then goes on to give a pretty fair and reasonable account of Carbon 14, and tells us that this clock is ‘zeroed’ when a living creature dies. Though, once again, there are problems with this dating method, as it is not used in this book for dating fossils we will leave this method alone at the moment.
“At present, the applicable isotopes all agree with each other in placing the origin of the Earth at present between four and five billion years ago. And they do so on the assumption that their half lives have always been the same as we measure them today- as the know laws of physics strongly suggest they should.” P107
He does mention briefly one more ‘evolutionary clock’, the molecular clock, but this is left for another chapter, so we won’t discuss that one here.
As is the norm, in this chapter, and throughout the book, there are very few footnotes, or notes in general to scientific papers, and any problems are glossed over. In this statement, RD wants to give us the impression that the age of the Earth has been shown to be 4.6 billion years old with a good degree of certainty. He does not though point out any experiments carried out on rocks, or the problems associated with this technique. He does not point out that this date relies heavily on a lot of assumptions and inference, which may not be accurate.
So in summary of this chapter, we have been shown how fossils, layers and the Earth are dated, by using ‘radioactive clocks’. I have tried to highlight some problems there are with these methods. If any of the assumptions that these dating methods are incorrect, then the dates of not only the fossils but the layers themselves are effected.
Can we really rely on half-life measurements which are many times longer than the presumed age of the universe? Are the rates of decay really constant and as ‘precise’ as RD would have us believe?
Do we really ‘know’ for certain that the clocks were ‘zeroed’? If not the findings are invalid and dubious. Does it really take millions of years for fossils to form and layers to be laid down?
At least RD has finally given us his first piece of ‘evidence’ for evolution, after 100 pages.
Organisms only appear in certain sequences in certain layers.
Has he offered any ‘evidence ‘to back up this statement? I would say no.
But, is this ‘evidence’ ‘better than any eyewitness testimony’ in any court EVER? Is it beyond reasonable doubt? My answer is no, it is not ‘beyond any reasonable doubt’, it is based on too many unproven assumptions, which if any are shown to be false, the ‘dating game’ becomes uncertain.