New method for dating pottery
Researchers at the University of Bristol (England) have developed the first direct method of dating ancient pottery, through analysis of animal fats preserved inside the ceramic walls. The new technique will allow more accurate determination of the age of pottery and, by extension, the age of associated artefacts and sites.
Although chemical analysis has, in the past, been used on residues found on the surface of pottery and shards, contact with the soil was always likely to produce corrupt data. Now research carried out by Richard Evershed, Ph.D and colleagues from the University has discovered that lipids (animal fats) are preserved through absorption into the material, in large enough quantities to allow radiocarbon dating. “Lipids are absorbed because most interesting pottery of any respectable age is unglazed,” says Evershed. “We’re taking a piece of pot and grinding it to a powder, and then extracting lipid that’s penetrated right down into the fabric.” A technique called capillary gas chromatography isolates the lipids. Purified compounds are then radiocarbon dated using an accelerator mass spectrometer at the Oxford University Radiocarbon Accelerator Unit.
Pottery is essential for dating archaeological sites. Although organic material can be dated by radiocarbon techniques, the results are not always reliable. Wood, for instance, can decompose over time; and animals often move bones around a site. Ceramics, on the other hand, have a long and stable lifespan. Later pottery can be easily dated by typology, but earlier ceramic material can be much harder because of its crude appearance. In the earlier research that led to the development of the new technique, Evershed’s team found the first direct evidence that people were dairy farming in Britain as long as 6,000 years ago. The prominence of fats in material from Neolithic, Bronze and Iron Age sites is consistent with their wide range of uses in the ancient world: lubricants, waterproofing agents, cosmetics, ointments, perfumes, varnishes, etc.
The researchers have now analyzed 15 pieces of pottery ranging in age from 4000 BCe to the 15th Century AD. These were blind-dated using the new method and then compared with verified dates. In all cases there was good correspondence of blind and validated dates. Evershed and his colleagues now plan to study mummies. “A lot of mummies were exported out of Egypt by the Victorians, and they often applied modern treatments to preserve them.” The researchers hope to distinguish between modern treatment and the original embalming agent.
According to Evershed, his method could be used to date any material that has preserved organic compounds. “You could even isolate individual amino acids by this preparative GC approach, but no one’s tried that. That’s the next step.” Evershed’s findings were featured ‘Analytical Chemistry’, the journal of the American Chemical Society.
Source: American Chemical Society (29 September 2003)
Dingoes descended from domestic dogs
New genetic research has shown that Australia’s wild dingoes are descended from domestic dogs introduced from South East Asia some 5,000 years ago. Additionally, the new analysis reveals only small mitochondrial DNA differences in a sample of 200 dingoes from all over Australia, suggesting that that all living dingoes are descended from very few ancestors – possibly just one breeding pair.
Until now the ancestry of the dingo has been much debated: time of arrival, region of origin, wild or domestic. “There hasn’t been a lot of evidence, so everything has been speculation,” says Alan Wilton, of the University of New South Wales. Wilton, with colleagues including Peter Savolainen at Stockholm’s Royal Institute of Technology, studied a highly variable portion of mtDNA from dingoes, dogs from all continents, and wolves. They also compared their results with mtDNA sequences of dogs and wolves published by Savolainen in ‘Science’ in 2002. “And we found that dingoes fall right into the main domestic dog clade,” says Wilton.
The earliest archaeological evidence for dingoes dates back 3,500 years. Wilton says that the new date of 5,000 years derived from his analysis is consistent with this, and with the expansion of Austronesian culture into the islands of SE Asia, 6,000 years ago. Dingo ancestors may have been brought by Malaccan trading boats, most likely as a food source, and quickly took to the wild. ”It’s not hard to imagine that as soon as they got here, some would run off and spread rapidly throughout the country.”
Source: New Scientist (29 September 2003)
