Chapter 4 turns to the topic of time. Here Richard Dawkins is targeting young-earth creationism and its denial that Earth has an ancient history. Ancient time is essential for evolution to be believable. On the other hand, Christians are divided over whether the earth and universe is young or old, depending on Scriptural interpretations.

Young-earth creationism context

I took a personal interest in young-earth creationism myself, and investigated it over several years. Eventually, I concluded that the scientific evidence strongly supports an old earth and universe. I think young-earth creationists might consider me heretical for saying I was convinced by the scientific evidence (they would say I should trust the infallible word of God over the investigations of fallible humans). I do have a high regard for the scientific method, and I reckon it is founded on principles which are fully harmonious with the Biblical revelation of God’s creation and His character. So I expect that it is possible for humans to discover truth through the scientific method, with certain key caveats—most importantly, that the scientific method isn’t compromised with a priori presumptions of only naturalistic explanations.

Christians uphold the authority of God-inspired scripture. However, that doesn’t mean that scientific evidence is ignored—the scientific evidence may be convincing even to the point that Biblical interpretations must be questioned, and I believe it has on the point of the age of the earth. Such cases have occurred already, and history demonstrates that the flaw has been not with the Bible but with human interpretations of it—geocentrism for example. In the case of geocentrism, history may also demonstrate that the flaw originated not with a Biblical interpretation, but with human ideas that were erroneously attributed to the Bible. In the pursuit of the truth, if the Bible is true, growing scientific knowledge and growing understanding of Biblical revelation should converge harmoniously.

Argument for ancient time

Dawkins is targeting the young-earth world view in this chapter. Dawkins’ argument for ancient time in chapter 4 is founded on these three things:

1. tree ring dating (dendrochronology)
2. radioactive clocks
3. the nature of the fossil record

He also mentions molecular clocks, but those aren’t discussed until chapter 10.

Tree-ring dating

Trees grow annual rings, and the rings allow us to count years. Of course, a single tree generally lives for only hundreds of years (with a few spectacular exceptions). But tree rings can vary between years, due to various environmental effects. So a particular time period can apparently leave a distinct fingerprint on the tree rings of that time. Trees that live in an area at times that overlap may be correlated by the “fingerprint” on their rings. By finding a suitable overlapping sequence of old trees or tree timber, it can be possible to construct an overlapping sequence of ring patterns winding back over thousands of years. After that, given another tree or timber from the area, it is possible to inspect its rings and match it to the database of ring patterns, to date its history down to the year.

According to Dawkins, that method allows us to date as far back as 11,500 years. That isn’t especially remarkable for evolutionary time scales, but it does fly in the face of the time scales favoured by young-earth creationists—especially when you consider the young-earth estimated date of the Flood at 2438 BC. Old-earth creationists propose longer timelines, and/or a non-global (but universal for humanity) Flood. So in that sense, the most interesting thing about tree-ring dating is not what it says about evolution, but what is says about various creationism theories.

Dawkins doesn’t present the hundreds of years of dendrochronology as an argument against creationism, but rather just as a general warm-up of the broad concept of scientific dating using natural “clocks” of various sorts. He moves on to radioactive clocks, and that is evidently his primary argument for millions of years. Nevertheless, the dendrochronology does present young-earth ideas with some troubling implications. That is, if relatively “newer” trees can can take us back 11,500 years, then what does that imply about the fossilised forests? There is at least an implication of ancient time well beyond the usual young-earth dating of 6,000 to 10,000 years.

Dawkins briefly mentions other similar annual-layer dating methods, such as varves in river or lake beds, and coral growth patterns. The apparently annual varves of the Green River shale number about 6 million. That was among the evidence that I found quite compelling to support an old earth.

Radioactive clocks

Dawkins presents the case for millions of years using the evidence of radioactive clocks. He provides several pages on the underlying principles of atomic structure, radioactive isotopes of elements, nuclear (rather than chemical) reactions, and half-lives. After that, he explains potassium-argon dating in particular, where an igneous rock can solidify from a molten state with no argon present and some amount of radioactive potassium-40. From that, an igneous rock of today can be dated by measuring its ratio of potassium-40 to argon-40. There are other radioactive elements used for dating, although he doesn’t go into so much detail to explain them.

The radioactive clocks alone are evidence of an ancient earth, regardless of any association with fossils. But Dawkins also explains their connection with dating fossils. It can’t be done directly, since radioactive dating only works for igneous rocks (dating when they solidified from molten state), whereas fossils are found in sedimentary rocks. However, fossil ages can be deduced by:

1. The worldwide phenomenon of identifiable layers (and layer sequences) of fossil-bearing sedimentary rocks, bearing fossils characteristic to the layers
2. The presence of layers of igneous rocks overlying and underlying sedimentary rocks, in various locations around the world

In no single location is there a complete set of fossil layers of the famous “geologic column”, with accompanying igneous rocks to date all the layers. But through the world, there are apparently enough layers to discern a consistent pattern of fossil layers. And in various places, there are enough interspersed igneous rock layers to enable the fossil layers’ dates to be indirectly inferred by association.

Initially, I could sympathise with young-earth creationists’ skepticism: Is the data and the method solid enough to support the conclusion? I’m not an expert, but the young-earth creationists have had years of opportunity to argue about weaknesses in the data and the method. From what I’ve heard, their arguments are weak, and the case for old age is compelling.

Young-Earth Objections, and Isochron Dating

One argument against radioactive dating I’ve heard is, “But you must consider the assumptions”. That is, radioactive dating involves three assumptions:

1. The starting ratio of elements is known
2. There has not been contamination of the samples due to elements leaking in or out
3. The rate of radioactive decay has remained consistent over time

In this chapter, Dawkins doesn’t mention an elaboration of radioactive dating, known as isochron dating. I think it’s a pity he doesn’t cover it, because isochron dating seems to significantly strengthen the case for radioactive dating. The method uses multiple samples to generate multiple data points. Statistical analysis of the multiple data points enables a statistical measure of the confidence in the calculated age, pretty much eliminating the doubts about the first two assumptions above. The method raises radioactive dating to another level of sophistication and confidence.

As for that last assumption, young earth creationists propose that the rate of radioactive decay could have been significantly faster in the past, which could explain how the ages calculated from radioactive dating could be systematically too old. Where is the evidence that supports it? If such a hypothesis were true, it would have some significant implications for the laws of physics, and the history of the earth and universe. Young-earth creationists would have to elaborate an alternative theory of physics that elegantly incorporates a varying decay rate; it would have to be supported by evidence and not beset by problems. For example, it would have to explain how stars could have maintained stable nuclear burning as astronomers see them, despite a vastly faster radioactive decay rate in the past. They would also need to offer a good explanation of how such a vastly faster radioactive decay rate would not have caused destructive heating of the earth, since radioactive decay releases heat.

Isochron dating of meteorites quite consistently gives a result of 4.5 billion years. That calculation also correlates with ages calculated from non-isochron radioactive dating methods. Considering the results of radioactive dating and isochron dating, it seems that a sufficient body of data has been amassed that it can’t be plausibly dismissed, despite some known flaws and limitations. The evidence it presents for an old earth and universe does seem quite consistent and convincing.

Objecting to Flood Interpretation of Fossil Record

After talking about radioactive dating methods, Dawkins criticises the young-earth creationist interpretation of the fossil record being due to the flood. I couldn’t agree more with Dawkins on this point. I find the young-earth creationist flood geology to be especially scientifically untenable. The fossil record shows distinct creatures in their distinct layers. Flood geology attempts to attribute this to the varying ability of various creatures to escape the rising flood waters. This theory doesn’t stand up to scrutiny, for several reasons. Firstly, as Dawkins says, if the “fleeing flood waters” hypothesis were true, we would expect to see some sort of statistical distribution (eg Gaussian distribution) of creatures in the geological layers, according to their varying ability to flee the flood waters, but not an absolutely clean separation. Secondly, we wouldn’t expect plants and pollen to be separated into such distinct layers—yet they are.

Geology shows evidence of geological processes that require significant amounts of time to lay down each of the various layers, as well as different environmental conditions in different time periods (e.g. wet and dry; desert, flood and oceanic). The sheer depth and volume of geological strata is also beyond the plausibility of young-earth flood geology.

The Conflict Between Science and Young-Earth Creationism

The exploration of young-earth creationism has been an interesting journey for me, which eventually led to me being convinced by the scientific evidence that young-earth creationism is not true. Rather, I conclude the earth and universe are old, for many of the reasons outlined in this chapter of Dawkins’ book.

Ken Ham, the famous young-earth advocate, argues passionately that Biblical authority is at the crux of the clash between science and creationism. And he evidently sees it as a clash of ideologies, a battle of authority between God and fallen humanity. Ken Ham observes that many young people who grow up in a church have a crisis of faith when they reach the university level, and the majority end up leaving the faith. He reckons the solution is to stand up for the authority of the Biblical revelation, defending it against the misguided efforts of scientific discovery that are contrary to God.

I see the situation profoundly differently to Ken Ham. I see the scientific method not as something to be fought against by Christians, but as a method that is fully harmonious with the Biblical revelation about God’s character, and therefore something Christians should embrace. If the Bible is true, Christians should be able to do science and see how scientific evidence is in harmony with the Biblical revelation. If there is a conflict, then we take a closer look at our interpretation of both the scientific data and the Biblical text.

In the case of Ken Ham and other young-earth creationists, I appreciate in principle their desire to defend the reliability and authority of the Bible, but I reckon they crucially misinterpret both the Biblical text and the scientific data, at a high price. As long as they continue to insist on their young earth interpretation of the Bible, in the face of such strong scientific evidence for an old earth, they actually contribute to the phenomenon of young people abandoning their beliefs. If a young person is led to believe that the young-earth Biblical interpretation is the only interpretation, no wonder they have a crisis of faith when they see compelling scientific evidence for an old earth.