In the 1940s Willard Libby realised you could use the decay of radiocarbon to date ancient artefacts. Soon, he began examining items of a known age to test his idea. These results agreed with the historical dates, confirming carbon dating can accurately tell how old stuff is1.

Some of Libby’s first tests, comparing carbon age and expected age1

These sorts of experiments continue today, helping us refine the accuracy of carbon dating and figure out why it sometimes doesn’t work. Thanks to these continuing experiments, pretty much every scientist is convinced that carbon dating is reliable when used right.

Except, of course, young earth creationists. They’re still skeptical, despite all of this research3.

Enter Davidson and Wolgemuth. They’re American geologists who have been carrying out Libby-style experiments on things of a known age in a Japanese lake. It’s their hope to see if any of these creationist arguments hold water when put to the test2,4.

Testing carbon dating

Libby dated things he found in the museum. Davidson and Wolgemuth, meanwhile, have several decades of extra science to play with. As such, they’re able to study twigs and mud of a known age from Lake Suigetsu, Japan.

How do we know the age of these twigs and mud?

Well, each tree ring typically represents a year of growth; giving us a good idea of how old a tree was. These growth patterns will vary slightly based on the environment over the years, giving each decade a unique fingerprint in the tree. Using this, we can align multiple trees together to find their age4.

Lining up rings from different tress to produce a longer chronology

The mud deposits – called varves – work in a similar way. Each year a new layer is deposited on the bottom of Lake Suigetsu. Around spring, the mud is lighter as growing algae shells get mixed in. As the algae become less common, the layers become darker towards the end of the year. Then Bam! New spring, new algae, new lighter phase. The clock has turned over4.

Varves from Lake Suigetsu, with the alternating layers visible4

Of course, figuring out you have a 5,000-year-old stick or a 12,000-year-old pile of mud isn’t that helpful. Crucially, Davidson and Wolgemuth looked at the radiocarbon content of these items. Given their alleged age, they figured out how much they radiocarbon expected to find.

If carbon dating really is reliable, all of this should line up, like in Libby’s experiments. Plot twist: it did4.

Complaining about carbon dating

Of course, 70 years of research hasn’t convinced young earth creationists. So, in a shocking turn of events, they also rejected these new results. Answers in Genesis was at the forefront of this, giving all too familiar critiques3.

What if multiple layers were put down each year? What if radiocarbon was produced at different rates over time? How can we be sure the tree rings and varves are the same age3?

So Davidson and Wolgemuth went back to their data. They began testing to see if any of these alternative theories could explain the patterns they saw.

Carbon in tree rings under creationist models. If radiocarbon dating is reliable, it should fall in the blue lines4

For instance, if multiple rings or varves were formed in the same year, their charts should have flat parts. Periods where multiple rings have the same radiocarbon count, since they were deposited in the same year. Alternatively, if the rate of radiocarbon decay changed over time, the gap between the known age of a ring and its carbon date should begin drifting. Finally, if they haven’t properly aligned stuff, the radiocarbon results should jump around rapidly4.

I’m sure you’ll be shocked to hear that, after retesting their data, Davidson and Wolgemuth found the creationists were wrong. The amount of radiocarbon present in the varves and tree rings was consistent with carbon dating being reliable. They didn’t find any trace of the jumps or plateaus expected under the creationist model4.

Radiocarbon content of tree rings and varves, which fell within expected parameters (blue lines)4.

Blown out of the dead sea

To really hammer this point home, they began examining the radiocarbon content of other artefacts that we have a date for. Artefacts like the dead sea scrolls.

Like with the varves, Davidson and Wolgemuth figured out how much radiocarbon content they should have for their age.

It all lined up beautifully.

The dead sea scrolls, dated to 2,230 years old, had the same radiocarbon content as tree rings allegedly the same age, confirming the accuracy of both the carbon date and estimated tree ring age4

References

  1. Arnold, J.R. and Libby, W.F., 1949. Age determinations by radiocarbon content: checks with samples of known age. Science110(2869), pp.678-680.
  2. Davidson, G., and K. Wolgemuth. 2010. Christian Geologists on Noah’s Flood: Biblical and Scientific Shortcomings of Flood Geology. Grand Rapids, Michigan: BioLogos Foundation. 
  3. Do Varves, Tree-Rings, and Radiocarbon Measurements Prove an Old Earth? Answers Research Journal
  4. Davidson, G. and Wolgemuth, K., 2018. Testing and Verifying Old Age Evidence: Lake Suigetsu Varves, Tree Rings, and Carbon-14. Perspectives on Science & Christian Faith70(2).

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4 Comments

Paul Braterman · 1st November 2018 at 3:19 pm

The abstract to Davidson and Wolgemuth, your lead story, is publicly accessible, and the full text will be in January. Note also where it was published: Perspectives on Science & Christian Faith. They are also among the authors of The Grand Canyon, Monument to an Ancient Earth, as well as the Biologos paper that you cite

    Adam Benton · 8th November 2018 at 1:36 pm

    They sent me the full text early for this post. It does make fascinating reading, so I’ll be sure to push it once it becomes more widely accessible.

Ashley Haworth-roberts · 1st November 2018 at 4:28 pm

I’ve had brief email contact with Davidson and Wolgemuth and am emailing them the link to this article for information (I read their 2018 paper online a few months back). They are Christians rather than atheists as you may know. But AiG would regard them as ‘compromisers’ siding with atheists. Because they side with science over the real age of the Earth.

    Adam Benton · 8th November 2018 at 1:40 pm

    They already know about it; they sent me their article for a post in the first place

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