Radiocarbon dating, sometimes called Carbon-14 dating, uses the properties of Carbon-14, one of carbon’s radioactive isotopes to determine the age of organic materials.
The method is based on the fact that Carbon-14 is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting radiocarbon then combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis.
When animals eat the plants, they acquire the Carbon-14, and when people eat the animals, they, in turn, acquire the Carbon-14. When the animals or plants die, the exchange of carbon with the environment stops and from that point on, the Carbon-14 begins to decrease, or decay, at a rate based on the half-life of the Carbon isotope. It is actually a straightforward idea and today, it is reliable in material dating back to 50,000 years ago.
When radiocarbon dating was first introduced, measurements were originally done by beta-counting devices, which counted the amount of beta radiation emitted by decaying Carbon-14 atoms in a sample. Now, we have accelerator mass spectrometry, and it has become the method of choice. It counts all the Carbon-14 atoms in the sample and not just the few that happen to decay during the measurements.
The Canadian Archaeological Radiocarbon Database (CARD)
The Canadian database was created by Dr. Richard “Dick” Morlan of the Canadian Museum of History (formerly the Canadian Museum of Civilization). CARD was set up in 1980 and currently holds 70,000 radiocarbon records from 70 countries. It is undergoing an expansion that started in 2014.
Most of the radiocarbon measurements in CARD are from samples derived from archaeological sites in North America, and of course, the database relies on archaeologists and researchers providing the dates of samples and other data pertaining to the find.
Part of CARD’s expansion efforts is to make the software behind the site open source, allowing research groups to set up their own version of CARD while still contributing core information to the main database. In this instance, the first such site is expected to come online within the next year, reports Nature.
There are other radiocarbon databases in the world, but CARD is the largest, says Robert Kelly at the University of Wyoming in Laramie. He is contributing data to CARD and he says CARD is the only database that has global ambitions. He says, “This is big data. That’s where the action is,” says Kelly. “We’ve spent 60 years running radiocarbon dates, and you can do a lot with them if they’re all in one place.”
The advantages of CARD wanting to go global
When doing radiocarbon dating, researchers have to take into account a bunch of different factors during the analysis, including the type of material being tested and variations in the rate at which the organic matter incorporated different carbon isotopes, in order to get an accurate age.
Thomas Stafford, a radiocarbon-dating consultant in Lafayette, Colorado says that in the past, this information wasn’t published alongside the carbon dates. He says a global database would have all this information with each carbon date so that if a data point needs to be recalculated, it can be done.
And another point in favor of a global database is the ease that would come from finding previously published radiocarbon data. “I’ve been working in my area for 20 years, and just last month I found a data set I didn’t know existed,” says Andrew Martindale, an anthropological archaeologist at the University of British Columbia in Vancouver and director of CARD.
However, Kelly says the most “compelling” reason for a global database is that it would allow data mining. Some experts argue that this would allow far-reaching research into making population estimates, as well as tracking how human populations moved over a given space and time.
Data mining is a computer process that is useful in discovering patterns in data sets using various methods at the intersection of machine learning, statistics, and database systems. Data mining is not the mining of data itself, but it is the extraction of patterns and knowledge.
In the days before computers, we did data mining by going through an encyclopedia, papers and other reports, writing down notes and points of reference. Then we plotted the information all out in front of us and came up, if we were lucky and if we had extracted the right information, with a pattern, and thus, knowledge. It’s a lot easier today.
Interestingly, in 2015, Martindale and his colleagues used CARD to create a continent-wide map of human population in the Americas over the past 13,000 years. Now, Martindale is looking at an even bigger project. He plans to use data mining to confirm and quantify North American population changes due to wars or settlement relocations. This information has, until now, been based on Indigenous traditional stories.
The disadvantages of CARD going global
Just like the site of the underwater cypress forest off the Alabama coast not being published, precise locations must be kept secret in many countries because of the fear of looting or just plain destruction of the site by some people. Added to this, some metadata, including the context of the find or the exact method of testing can be difficult to standardize.
“There is a lot in a date. It’s not just a number,” says Tom Higham, deputy director of the Oxford Radiocarbon Accelerator Unit in the United Kingdom. His big concern is jamming all the data about one site into a single database. And more worrisome is trying to get permissions from people who own the data, a formidable task in itself. Higham says this may be a “worthy but fruitless” endeavor.
However, despite the naysayers, CARD is upbeat about the idea. “The data belong to the people who paid for it,” says Martindale. “But if we make it easy for them, just a button they can push that says ‘yes, upload my data to CARD’, then we think they will.”
