Fish-based diets can cause headaches for archaeologists
To get a radiocarbon date, one measures the amount of remaining Carbon-14 atoms in a sample. The less Carbon-14 left, the older the sample.
“Hard water contains less Carbon-14 than the atmosphere, because dissolved carbonates are Carbon-14 free. A fish caught in hard water has thus a higher Carbon-14 age than contemporaneous terrestrial samples. If such a fish is then cooked in a ceramic pot, the radiocarbon age of the food crust will be higher than if a terrestrial animal was cooked in the pot,” PastHorizonsPR.com said.
It said this is called the “reservoir effect” because “the fish’s carbon actually comes from another ‘reservoir’ than the carbon in terrestrial animals from the surrounding area.”
Hmmmmmm. My first thought was to wonder how this might affect dates on people who consumed the fish as well. There’s a mini-lecture on C14 reservoir effects at the link as well.
The latest issue of New Scientist has an article summarizing findings from a paper in the journal Science, discussing how lake sediments in Japan may provide a new way of calibrating C14 dates.
It is hoped that the sediments will provide accurate calibration back to 60,000 years ago (current calibration techniques only extend back c. 12,500 years).
The article also has, in typical New Scientist fashion, a helpful couple of lines explaining what radiocarbon dating is all about.
There’s also a longer summary of the paper on the EurekAlert website and another version on the Nature website.
Journal reference: Science, DOI: 10.1126/science.1226660
Archaeologist Ashley White has found artifacts on his property in Marion County, Florida, that strongly indicate that he has found the site of Potano, visited by De Soto in 1539. Temporal and cultural identification of the artifacts comes from the minting date of a Spanish coin found at the site, and the technological attributes of the chain mail (manufactured by methods that went out of favor by the 1600s). They also found a domesticated (European-introduced) pig jaw at the site, and glass beads found there are consistent with the date and cultural affiliation. I love it when dating can be done without expenive radiometric procedures, and I also love it when zooarchaeology can come to the rescue. Personally, I have been fascinated with the De Soto’s travels in what is now the U.S. for several years (especially the descriptions of the Yazoo area), and the more I learn about DeSoto, the weirder his life story seems to be. It wasn’t until 1997 that I learned he died in Arkansas and it wasn’t until 2003 (I’m just slow) that I realized that he also traveled to South America and was one of the first Europeans to interact with the Inca (whether you consider that to mean “Inca people,” “Inca empire,” or “Inca/King” — it works for any of the meanings of that word).
I am totally convinced by the evidence that this is a De Soto site, and here’s the clincher: Jerald Milanich is quoted saying:
There is absolutely no doubt that is a De Soto contact site, and I am 99.99 percent sure this is the town of Potano
For more links (text and some maps & photos):
I am currently waiting for my radiocarbon dating results so that I can make plans on how to date the rest of my sediments. I took a 143-cm long core at an archaeological site. I was hoping to get at least a 3,700 year sediment record, but I am thinking what I got was only recent/historic sediments. There are ways of checking, and I am thinking of using 137Cs (which is an unstable isotope of Cesium with a short half-life of only about 30 years ) or using 210Pb (which is also short lived, in the archaeological sense, with a half life of 22.3 years) to get chronological control on my relatively young sequence. As they say, archaeologists will do almost anything for a date (but we hate waiting or getting bad results) …
Spanish Cave Paintings’ Age Questioned by Archaeologist
Cave paintings in Spain need to be analyzed further before the works can be confirmed as the oldest known examples in the world, an archaeologist said, casting doubt over a paper published in the journal Science.
A team led by Alistair Pike of the University of Bristol in England said in the paper that paintings at El Castillo cave date back at least 40,800 years. That would make them about 4,000 years older than those at the Chauvet cave in France, meaning the Spanish works could be the only cave art ever found to have been painted by Neanderthals, according to Pike.
This site was mentioned in the link below.
Archaeology: Date with history
Most of the thousands of carbon dates from archaeological sites from the Middle-to-Upper Palaeolithic era are wrong, say scientists, perhaps even as many as 90%. As a result, archaeologists can agree on the history of this era only in the broadest of brushstrokes.
Tom found himself drawn to the quantitative side of archaeology to help fill in those details. His father had counselled that if he wanted a future in the field, Tom ought to join the push to make it a more rigorous science, emphasizing testable theory, experiment and statistics. So, at his father’s urging, Tom applied for and completed a PhD at the University of Waikato’s Radiocarbon Dating Laboratory in Hamilton, then did a postdoc there. And when a faculty position became available at a better-funded lab at the University of Oxford in 2000, he moved back to his birth country.
Any idea that archaeology hasn’t gone in the direction that Charles predicted is dispelled by a visit to his son’s workplace. Its centrepiece is a giant £2.5-million (US$4-million) particle accelerator, which is used to tot up the number of radioactive carbon molecules in a sample.
Good article (doesn’t he look like Bob Geldof in that photo?) Nature also has a special Peopling the Planet issue, though I don’t know how much is open to the public online.
Dated my first historic artifact, that is. Well, maybe not the first, I’m fairly certain that I’ve done something similar with some odd objects or other in the past, but this one was actually recovered on an archaeological project — monitoring anyway — and, without the date actually being stamped on the thing, I have assigned a secure date for its manufacture. To wit:
It’s got a makers mark of an overlaid diamond and ‘O’ (see here) with a 20 to the left and a 2 to the right. It’s also got “Duraglas” stamped into the side. I found that this was an Owens-Illinois Glass Co. bottle and their Duraglass product was not produced until 1940. The 20 represents its Oakland CA plant — 20 had been used until 1940 for it Backinridge, PA plant also — and the ‘2′ represents 1942. . . .hmmmm. Something doesn’t make sense. Before 1940, the date digit was supposed to represent the last digit of the year — 0 for 1931, 1 for 1931, etc. — but after 1940 they either added a period to indicate 1940+ or two digits — 4. or 44 = 1944 — but this has no period, but if Duraglas wasn’t used until 1940. . . . .a quandary. Maybe I’m not as certain as I thought. Well, needs more study, I think. Seems to be a beer bottle as well, since I have read that the stipling it has was used in conjunction with the script ‘Duraglas’ for beer bottles. Well, at any rate, I was quite thrilled at at least begin to pin a date on something. Hopefully, I can resolve the discrepancies at some point.
Smithsonian develops technique to date silk items
Conservation scientists have developed a new technique to authenticate and determine the age of silk artifacts held in museums and collections, the Smithsonian Institution announced Monday.
Carbon dating is too destructive for most silk items, scientists said. The new method uses the natural deterioration of silk’s amino acids to determine its age by calculating that change over time — a process known as racemization. Archaeologists and forensic anthropologists have used this process for years to date bones, shells and teeth.
I was wondering why C14 wasn’t an option, but of course its destructive although AAR is also destructive. . . .admittedly, I haven’t really studied the method very much, although from what I remember it’s been generally thought of as being potentially inaccurate due to the environmental influences on the reaction.
Carl sent me a notice (actually it was more like a berating) of its publication and it is, so far, open access so y’all can go read it yourselves: High-precision radiocarbon dating shows recent and rapid initial human colonization of East Polynesia (Janet M. Wilmshurst, Terry L. Hunt, Carl P. Lipo, and Atholl J. Anderson)
The 15 archipelagos of East Polynesia, including New Zealand, Hawaii, and Rapa Nui, were the last habitable places on earth colonized by prehistoric humans. The timing and pattern of this colonization event has been poorly resolved, with chronologies varying by >1000 y, precluding understanding of cultural change and ecological impacts on these pristine ecosystems. In a meta-analysis of 1,434 radiocarbon dates from the region, reliable short-lived samples reveal that the colonization of East Polynesia occurred in two distinct phases: earliest in the Society Islands A.D. ∼1025–1120, four centuries later than previously assumed; then after 70–265 y, dispersal continued in one major pulse to all remaining islands A.D. ∼1190–1290. We show that previously supported longer chronologies have relied upon radiocarbon-dated materials with large sources of error, making them unsuitable for precise dating of recent events. Our empirically based and dramatically shortened chronology for the colonization of East Polynesia resolves longstanding paradoxes and offers a robust explanation for the remarkable uniformity of East Polynesian culture, human biology, and language. Models of human colonization, ecological change and historical linguistics for the region now require substantial revision.
The link is to a PDF and if it doesn’t work, just go to the PNAS web site and do a search on the authors. Only 6 pages so not a major challenge to work through it and there’s a lot of good stuff in there, especially on the requirements of carbon dating.
I need to revise my area of specialization as the south Pacific seems vastly preferable to Egypt.
by someone doing everyday things. This time, someone was putting in a driveway on their private property when, BIG bones came up. It turned out to be the Wenas Mammoth Site, currently under investigation by folks at Central Washington University. Now is it archaeological, or just an Ice age paleontological site? Further analysis will be needed to answer whether humans were involved — a possible flake (artifact) was found near the mammoth bones. Why would this be important? We do have other mammoth sites, but this one is radiocarbon dated to 16,000 years ago. Human involvement would make this an unexpectedly and exceptionally OLD site. Currently, the oldest accepted site in North America is Paisley Caves, Oregon, with a human presence dated to about 14,000 years ago. (If you haven’t read about Paisley Caves, oh, you are in for a treat).
One of the things that makes this special, besides the possible involvement of ancient humans, is that this mammoth actually lived and died in eastern Washington. Most mammoths found in eastern Washington came from Idaho. They got caught in one of the most massive floods in history – the Spokane Flood (released from glacial lake Missoula). Imagine the scene of tumbling water, boulders, elephants, etc. Incredible! This mammoth, from Wenas, however, was found above the flood deposits, so it was a local beastie. Another thing to note from the news story on the site: only portions of the site were excavated — the rest is being left/conserved for the future. Cool! (Okay, the Ice Age is inherently cool). What is also cool is that I once got to unpack an extinct giant short faced bear skull from Wenas (also Ice Age).