"Everything that has come down to us from heathendom is wrapped in a thick fog; it belongs to a space of time that we cannot measure. We know that it is older than Christendom, but whether by a couple of years or a couple of centuries, or even by more than a millennium we can do no more than guess" [1]
Rasmus Nyerup 1806

Many of us are intimidated by science. Radiocarbon dating, a development in atomic physics, is a case in point. The importance of this scientific method, however, is far reaching, influencing a multitude of various and independent disciplines such as hydrology, geology, atmospheric science and archaeology to name but a few. However, we leave the actual task of understanding radiocarbon dating to the boffin elite – we accept their conclusions blindly, respect the precision of their equipment and admire their genius.

In truth, the principles of radiocarbon dating are astoundingly simple and readily accessible. Furthermore, the presumption that radiocarbon dating is an "exact science" is erroneous and in all fairness few scientists make this claim anyway. The problem is that the many individuals across many disciplines that employ radiocarbon dating as a dating device do not understand its nature or purpose. Lets put the record straight.

References:

  1. Rasmus Nyerup, Oversyn over foedrelandets mindesmaerker fra oldtiden

Principles of Radiocarbon dating

William Frank Libby and his team developed the principles of radiocarbon dating during the 1950s. By 1960 their work was complete and in December of the same year Libby was presented with the Nobel Prize for Chemistry. One of the scientists who nominated Libby for the award commented:

"Seldom has a single discovery in chemistry had such an impact on the thinking of so many fields of human endeavour. Seldom has a single discovery generated such wide interest" [2]

Libby discovered that the unstable radioactive component of carbon (C14) disintegrated at a predictable level against the stable elements of the carbon composite (C12 and C13). All three of these isotopes occur naturally in our atmosphere in the following proportions: C12 – 98.89%, C13 – 1.11% and C14 – 0.00000000010% [3].

The stable isotopes of carbon (12 and 13) were formed when all of our planet’s atoms materialised –a long, long time ago [4]. C14 is formed, albeit on a miniscule level, due to bombardments of cosmic rays that hit our planet, on a day-to-day basis, and interact with our atmosphere [5]. These rays strike the earth’s existing atoms and break them up leaving the neutrons of these atoms to float around our atmosphere.

A carbon 14 isotope is formed when one of these floating neutrons merges with the nucleus of a nitrogen atom [6]. Radiocarbon, therefore, is a kind of Frankenstein isotope, a fusion between different atomic elements. These rogue carbon 14 isotopes, which are produced at a steady rate, are then oxidized and absorbed into the biosphere through the process of photosynthesis and the natural food chain [7].

Consequently all living things incorporate the atmospheric ratio of C14 to C12 in their geographical area, which is maintained by their metabolic rate [8]. Once dead, however, living organisms stop absorbing carbon and it is the behaviour of C14 after this point that is interesting. Libby discovered that radiocarbon decays with a half-life of 5568 years [9]. This means that after 5568 years or so, half of the original amount of C14 would have disintegrated from the sample. After another 5568 years, again, half of what is left dies.

Therefore, with the original amount of C14 to C12 being a geological constant [10], the age of a sample can be determined by measuring the residual C14 present. For example, if one quarter of the original amount of C14 is present then the organism in question died two half lives ago (5568 + 5568), which equates to an age of 10, 146 years.

Herein lie the basic backbone principles of radiocarbon dating as a tool of science and archaeology. It is a fact that radiocarbon is absorbed into the biosphere. It is a fact that when an organism dies no more C14 is absorbed. It is a fact that C14 spontaneously dies after this point. It is a fact that this process can be measured.

References:

  1. Quoted in Taylor 1987
  2. Higham, Thomas, http://c14dating.com/int.html
  3. Hedges, Robert, E. M, http://humanist.net/appro-sindone/hedges.html
  4. Renfrew, Colin, Before Civilization (1973), Pg 255
  5. Ibid
  6. Gove, H. E, Carbon Dating The Turin Shroud, 1996, 11
  7. Taylor, R. E, Radiocarbon Dating, 2 (useful illustration)
  8. The actual duration of the “Half Life” has never been universally accepted, Taylor 4, Renfrew, 261-262
  9. Levine, Mary Ann, Accommodating Age – Archaeology of Eastern North America, Volume 18, 1990, 33. This will be discussed later on

Into The Laboratory

With all of these facts (and they are facts), it is confusing then to pick up Radiocarbon (Journal that lists worldwide radiocarbon laboratory results) and read:

"Six reputable dating laboratories performed 18 age determinations on wood from Chelford, Cheshire. The finite ages reported ranged between 26,200 and 60,000 BP [11], a spread of 34,600 years" [12]

Here is another fact for you; whilst the theory of radiocarbon dating is convincing, when its principles are practically applied to samples in a laboratory human processes come into the fray. In short mistakes are made, big ones. Furthermore, samples are contaminated in laboratories by background radiation that can and do pollute the residual level of C14 to be measured [13].

As pointed out by Renfrew in 1973 and Taylor in 1986, Radiocarbon dating relies on a series of unsubstantiated assumptions that were made by Libby when he was developing his theory. For example there has been much debate in recent years about Libby’s measurement of the half-life to 5568 years. Indeed, today it is generally agreed that Libby was wrong and that the half-life of C14 is actually closer to 5730 years [14]. This is a discrepancy of 162 years and becomes very significant when dating samples thousands of years old.

But with his Nobel Prize for chemistry came complete belief from Libby in his new system. Libby radiocarbon dated Egyptian archaeological samples that had already been historically dated – the ancient Egyptians kept good records of their chronology. Unfortunately Libby’s results kept coming up to young, in some cases by 800 years. Amazingly though, Libby concluded,

"This plot of the data suggests that the Egyptian historical dates beyond 4000 years ago may be somewhat too old, perhaps five centuries too old at 5000 years ago" [15]

This is a classic case of scientific arrogance and blind religious belief in the superiority of the scientific method over the archaeological – Libby was wrong, his method had failed him. Now this problem has been addressed but has this attitude of self-authority given radiocarbon dating a reputation above its level of reliability?

Similar problems such as these, and there are many of them [16], have been addressed and are accounted for in modern radiocarbon studies. However, my research has indicated that there are two serious issues of concern with radiocarbon dating that still cause serious problems today. These are 1) Sample contamination, 2) Measuring the levels of C14 in our atmosphere over the geological ages.

References:

  1. BP means before present – this date is set at 1950
  2. Switsur, Roy Radiocarbon 1990, V0l 32, No. 3, 341
  3. Renfrew, 257
  4. Wigley and Muller 1981, 176
  5. Libby, Willard, “The accuracy of Radiocarbon Dates”, Science, 140, 278-9 (1963)
  6. See Renfrew, 261-268

Sample Contamination

Mary Levine states, "Contamination refers to the existence of nonindigenous organics in the sample that were not formed together with the sample material" [17]

Many pictures from the early days of radiocarbon sample collection operations show scientific experts smoking cigarettes. Not very clever boys! As Renfrew points out – "drop a little ash onto your – soon to be chemically analysed – samples and you’ll get the radiocarbon age of the tobacco plant that was used to make your cigarette" [18].

Although such methodical incompetence would never be tolerated today, archaeological samples still suffer from contamination. Known contaminants and how to deal with them are discussed in Taylor (1987). He groups major contaminants into four categories 1) physically removable, 2) acid soluble, 3) base soluble, and 4) solvent soluble. All of these contaminants, if not removed, can drastically influence the age determination the laboratory will come to for a sample [19].

H. E. Gove, one of the developers of Accelerator Mass Spectrometry (AMS), radiocarbon dated the Turin Shroud. The conclusion he came to was, that the fibre used to weave the shroud dated to AD 1325 [20].

Whilst Gove and his team support the authenticity of their findings completely many, for obvious reasons, believe that the Turin Shroud is older. Gove and his cohorts defend all of their criticisms expertly and if I had to choose a lane I would say that the scientific dating for the Turin Shroud is probably correct. Even so, the level of criticism that has been thrown at this particular project, illustrates how much can go wrong with radiocarbon dating and how suspicious some scientists are of it [21].

The samples, it has been argued, may have been contaminated by younger organic carbon; the cleaning techniques could have missed any modern traces of contamination. Indeed Robert Hedges of Oxford University has stated: "It is worth noting that small systematic errors cannot be completely ruled out" [22]. I wonder if Hedges would explain the discrepancies in the dates reached by the laboratories dating the Chelford wood as the result of "small systematic errors"? Again are we being fooled by heavy rhetoric, are we taken in by the inner confidence present in scientific reporting?

With regards to the official dating of the Turin Shroud Dr Leoncio Garza Valdes would certainly think so. All ancient textiles are coated in a bio-plastic film produced by bacteria that Garza-Valdes believes can throw radiocarbon dates way off [23]. In fact, he argues that the Turin Shroud could well prove to be 2000 years old as the radiocarbon date for it cannot be taken as the final word; other evidence has to be considered. Interestingly Gove (although he disagrees with Garza Valdes) conceded that his criticisms warranted further investigation [24].

References:

  1. Levine, 36
  2. Renfrew, 263
  3. Taylor, 41-43, Levine, 36
  4. Gove, 1999, 159
  5. Gove, 1999, 161-169
  6. Hedges, http://humanist.net/appro-sindone/hedges.html
  7. Garza-Valdes, The DNA of God (1999), http://www.shroud.com/c14debat.htm
  8. Gove, Relic, Icon or Hoax, 308

C14 Levels In Our Atmosphere

Libby’s principlel of simultaneity, presumes that the levels of C14 in any particular geographical area has been constant and regular throughout the geological record. This presumption was integral to the validity of radiocarbon dating during the early years of its development. Indeed, you have to know how much C14 was present in an organism at the time of its death to be able to measure, reliably, how much of it has disintegrated. This assumption, as Renfrew points out, is not correct:

"It is now known, however, that the proportion of radiocarbon to ordinary C12 has not remained constant through time, and that before about 1000B.C. the deviations are so great as to make radiocarbon dates significantly in error." [25]

Advances in Dendrochronological research (the study of tree rings), shows conclusively that the amount of C14 in our atmosphere over the past 8000 thousand years has fluctuated significantly [26]. Libby was starting with a false constant. His research was based on erroneous foundations.

The bristle cone pine, a tree that grows in southwestern regions of the USA, lives for thousands of years. Some, that are still alive today, began their life four thousand years ago. Furthermore, dead bristle cone logs that have been collected from the ground in the areas they grow, extend the tree ring record back by a further four thousand years. The California sequoia and the European oak are other trees that are useful as they also live for thousands of years [27].

As everyone knows, for every year of growth trees produce annual rings. These rings can be counted giving the age of the tree in question. It made sense then that the level of residual C14 in a tree ring that was say 6000 years old could be predicted as the level of C14 in our atmosphere was the same then as it is today. Wrong.

Tree ring analysis has shown, for example, that that the level of C14 in our atmosphere 6000 years ago was much higher than today. Consequently, samples dated from that age were "scientifically proven" to have been much younger than they actually were [28] – a contradiction in terms. Thanks to the work of Hans Suess graphs for correcting C14 values to compensate for the geophysical fluctuations of our atmosphere have been devised [29]. However, this has heavily reduced the authority of C14 dates for samples that are older than 8000 years. We simply have no information on the level of radiocarbon in our atmosphere before this date.

References:

  1. Renfrew, 268
  2. Levine, 35
  3. Taylor, 21
  4. Renfrew, 70
  5. Suess, Secular Variations of The Cosmic-Ray-Produced C14 in The Atmosphere and Their Interpretations. Journal of Geophysical Research 70(23): 5937-5952 (1965)

Overview

Radiocarbon dating is a developing scientific method. However, at every stage of its development scientists have supported its overall integrity completely only to eat their words when a significant error of judgement or method is highlighted. Mistakes are made and not surprisingly when one considers the amount of uncontrollable variables the scientist has to take into account: atmospheric fluctuations, background radiation, bacterial growth, contamination and human error.

Radiocarbon dating, as part of a comprehensive archaeological investigation, is still extremely important; it just needs to be put into a cultural and historical perspective. How can a scientist completely disregard strong evidence to the contrary for dating an archaeological site just because his/her radiocarbon date indicates a different age? This is dangerous. Indeed, many Egyptologists upheld Libby’s presumption that the chronology for the old kingdom was wrong because it had been ‘scientifically proven’ to be so [30]. He was in fact wrong.

Radiocarbon dating is useful as a compliment to other data; this is when it is strong. Until the day comes that every variable can be controlled and every error eliminated radiocarbon dates will never have the final word on archaeological sites.

References:

  1. Renfrew, 73