Hello Everyone,
I was listening to a podcast tonight and they were discussing an ancient wood carving. They said when it was found it was believed to be something like 600 years old, but carbon dating a few years ago put the age at thousands of years old.
So my question is, I’m assuming they are able to date the wood to be thousands of years old. But can they date the carving? I mean if someone found a 2000 year old hunk of wood and carved it 20 years ago, it would date thousands of years old, but it was only carved decades ago. Besides pantina, how can you possibly date when a person carved an artifact?
For carbon dating, the date is usually for when the organic material it was made from stopped living, and thus the percentage of C14 out of the total Carbon was fixed and was not going to increase from interchanging carbon from its body and the atmosphere. C14 is constantly being created due to cosmic rays, but the rate of replenishment doesn’t necessarily equal the rate of decay, and so there are calibration curves based on having carbon dated artifacts with a known (or at least highly suspected) date to take into account the relative difference in the presumed atmospheric C14 percentage.
I suppose you could carve your name into dinosaur bones but that doesn’t make you 65 million years old. But realistically, if a piece of wood is with other burial objects the chances are good they haven’t held onto it for thousands of years only to bury it with that guy.
My deck is chemically treated and painted and that fucker needs replacement regularly.
Old wood effect / problem is one of archaeology’s ABC’s. Carbon dating tells when organic matter died, not when it was used. There is always a possibility that really old wood was used to craft a wooden item, but it’s not probable. Old wood (in the OP’s 2 000 year range) is exceedingly rare in most environs, and practically always inferior in strength and workability to recently (meaning decades at most) cut wood. The vast majority of wood used for carving, in the past or present, is young enough when utilized to fall within the +/- range of the carbon date in question.
Contextual and stylistic dating usually helps heaps to put a suspect C14-dated item into a realistic age range. But as per the question in the OP: strictly speaking, carbon dating dates neither the item nor when it was created. It dates the death of the raw material.
Context is everything. While you are dating the death of the wood, as has been discussed, its the find context, how it was used and deposited that tells archaeologists the likelihood of that piece of wood was cut up and used last week, last year or last century. In many places where timber preserves well, such as desert and dry country, timber is scarce so old wood is conserved and re-used where possible.
Another circumstance is bog wood, which can be preserved in anaerobic conditions for centuries, and may be desirable for some uses. That could throw you right out.
For archaeologists, the carving or final form may be of a style specific to a time and place, which is an independent check against radiometric dating. In some circumstances dendro-chronology [counting and analysing tree-ring sequences] provides another independent check against C14 dating, and this was used to create the calibration curves mentioned above.
This is 100% true and why it is absolutely critical for an archeologist to properly excavate an undisturbed site.
That way they get context clues from the where the artefact is found (depth) and what else is around it that can help date it, i.e: pottery jewellery etc.
If they found the wooden carving sitting on the top of the sand it tells them nothing except that the wood was 2000 years old. If they found the wooden carving buried under 6 feet of sand next to 2000 year old pottery (they can usually date pottery fairly accurately based on stylistic elements and the materials it was made from) that would give them strong evidence that it was carved 2000 years ago.
I’m a big fan of the British TV show “Time Team”. Every episode they hammering home the importance of context. BTW - If you like this topic, I highly recommend the show.
Does xylem continue exchanging carbon after it’s laid down in its ring? Plenty of trees can live for a thousand years or more-- Will the inner rings carbon-date the same as the outer rings?
Carbon dating is extremely sensitive and introducing a few atoms may change the dating significantly. It is important that the collector doesn’t contaminate the sample.
If the wood carver uses some plant derived material like oils (to soak the wood) or lacquers, that will also effect the dating.
“ When radiocarbon dating a piece of wood or charcoal, the event dated is the growth of the tree ring. Trees grow by the addition of rings, and these rings stop exchanging carbon with the biosphere once they are laid down. Thus, the radiocarbon age of a single tree’s heartwood and sapwood will not be the same with the innermost heartwood being significantly older than the sapwood.”
The thing is, a large percentage of ancient wood artefacts come from wetland sites with little to no context to work with. This is illustrated by the fact that numerous bog finds have proven to be of a very different age than their find context (the turf layer). This is explained by the ancient practice of burying items into bogs, for practical and ritual reasons.
Stray finds with nothing but a direct date contradicting the find layer date are business as usual here. I say this as a field archaeologist working in Northern Europe, awash with wood-preserving bogs.
ETA: dendrochronology is usually inapplicable to wood items smaller than building structures. There needs to be a long series of wood rings in the artefact for the method to work. Weapons, tools and ornaments rarely have enough rings in them.
Another dating problem is mollusk shells, since they incorporate a significant amount of carbon from the ground rather than the air, so they are much more carbon-14 deficient than a plant that lived at the same time.
Sure, different areas of the tree will likely have finished exchanging carbon at different times, but it’s not like it’s going to matter on the grand scheme of dating something given the inherent lack of precision of carbon dating. How often are people going to be using the inner wood from trees over a hundred years old? Radiocarbon dating is useful more for providing a very rough guideline when nothing else is known of its age.
All very true (and doubtless frustrating if that’s the norm). Abundant water-logged wooden objects is thankfully not my regular nightmare, but any surface finds and cumulative deposits where stuff just collects over millenia may have a much higher wow factor than actual useful info to easily give up.
Getting a date on a piece of wood that has been skittering around the landscape and eventually fallen into a bog or been grown over does not tell you much with any certainty about the date of any of the other things it was found with.
Given that radiocarbon or any form of dating costs money, archaeologists think hard about what objects give them the most info value and prefer, when possible, to get material that was reliably created in situ, like charcoal from a fire. Even then the question ‘is it old wood’ should be asked.
Charcoal from a fire is actually where the old wood problem is most pertinent. Historically, and by projection, prehistorically, it was common to use old, dead standing trees for firewood - already dry(ish), easy to break wood at hand in the wild.
For instance in the area I do field work in, there are pine trees that were 400 years old when they died, and then spent the next 100 - 200 years standing. Picture a piece of charcoal that came from the inner heartwood of such a pine tree (heartwood is dead wood, even in a living tree). That piece of charcoal will potentially date half a millennium older than the fireplace we are interested in giving an age.
Consequently, it is far better to date a piece of burnt bone from the fireplace than the coals. Present-day AMS technique allows for tiny samples to be dated.