Chemists Help Archaeologists to Probe Biblical History Collaboration Establishes a New Approach for Teasing out Clues Hidden in the Soil

nEWs in Focus brary.com I ol T o H rnold Travel/P rnold a ar/Jon H H. Isac H.

Was Tel Megiddo in Israel a regional centre of power in the fabled kingdom of David and Solomon?

arcHaeology Chemists help archaeologists to probe biblical history Collaboration establishes a new approach for teasing out clues hidden in the soil.

By Haim Watzman in tel megiddo working shoulder-to-shoulder at Tel Megiddo should become the norm for archaeology. and several other important Israeli sites. “In the “It’s definitely where archaeology is headed,” abled as a site of biblical battles and past, all too often, archaeologists and scientists says Ran Boytner of the University of Califor- spectacular palaces, Tel Megiddo today worked together, but it was two parallel lines,” nia, Los Angeles, an archaeologist who works is a dusty mound overlooking Israel’s says archaeologist Aren Maeir of Bar-Ilan in South America. “This is partly to do with the FJezreel valley. It is also host to one of the hottest University in Ramat Gan, Israel. It could take miniaturization of analytical tools and the low- debates in archaeology — a controversy over months or even years before finds were sent ering of costs, as well as a revival of interest in the historical truth of the Bible’s account of the away to the lab, he says, with results taking just archaeology, especially among senior scientists first united Kingdom of Israel. as long to come back. “On top of that, some- who are eager to get out of the lab.” Ancient Megiddo is said to have been a key times the samples weren’t taken correctly.” administrative and military centre in the king- The Tel Megiddo dig is different. Chemists ChemiCal Clues dom ruled by King David and his son Solomon make up half of the two dozen excavators on Archaeologists are trained to use their eyes to during the eleventh and tenth centuries bc. But the team, which is being led by Finkelstein and identify a stratum — a buried layer represent- the biblical narrative is challenged by archaeol- Steve Weiner, a structural biologist specializing ing a particular period of habitation. A black ogists such as Israel Finkelstein of Tel Aviv Uni- in mineralized tissues who is director of the stripe, for example, might be a burn layer — versity, who believe that David and Solomon Kimmel Center for Archaeological Science evidence of a hearth, or of the ransacking of a did not rule over an Iron Age empire. Instead, at the Weizmann Institute in Rehovot, Israel. city, depending on its size. Artefacts and pottery they suggest, David and Solomon commanded Funded by a European Research Council embedded in strata can also serve as markers for a small and not terribly influential kingdom, grant worth €3 million (US$4 million) over defining and dating them. But chemical analysis and Megiddo’s peak came nearly a century five years, the pair hope can add many more details to the picture. after the united kingdom had divided. Nature.Com that their work at Tel When Nature visited Tel Megiddo in October, Important evidence relating to this debate For more stories on Megiddo and elsewhere excavators were working with brushes, tweez- is being unearthed by a unique collaboration archaeology see: will show that this model ers and teaspoons to gather sediment samples between archaeologists and natural scientists, go.nature.com/8sigjq of close collaboration into small plastic vials before taking them to an

infrared spectrometer set up on a folding table at grains of wheat. After carefully photograph- the edge of the site. The chemical clues yielded ing and noting the context of the find, he col- by the spectrometer gave immediate feedback to lected kernels in a vial so that they could be the diggers as they collected further samples. sent abroad to a particle-accelerator facility Chemical analysis can distinguish between for dating. Boaretto is currently shopping for soil layers that look identical to the naked eye, a particle accelerator for her lab at Weizmann. explains Weiner. In a paper published this The machine, expected to cost about $2 mil- month, for example, he and his colleagues show lion, should be ready for radiocarbon dating how infrared spectrometry can reveal the dis- work in 12–18 months. Having an accelerator tinctive origins of seemingly identical layers of near to local excavation sites will help to yield calcite, a form of calcium carbonate (L. Regev results much more quickly, says Boaretto, and et al. J. Archaeol. Sci. 37, 3022–3029; 2010). her team will be able to supervise samples at Wood burnt at above 500 °C produces calcite, every stage from the dig to the accelerator, pre- although the mineral can also come from lime- venting contamination that could otherwise stone slaked to make lime for construction, and cast doubt on the analysis. is found in the soil used to make mud bricks. Boaretto explains that she is on site because Each type of calcite has a distinctive infrared an understanding of precisely where samples signature, providing information that helps came from is key to getting the most accurate archaeologists to distinguish between a floor, a dating. For instance, wheat grains and pieces wall or a kiln. of charcoal are often In another part of Tel Megiddo, Weiner Chemical used to date pottery points out a layer rich in a form of silica (SiO2) analysis can shards found in the that accreted in and around the cells of plants. distinguish same spot. But with- These ‘phytolith’ layers mark locations where between soil out seeing the stratig- vegetation grew or was stored. Weiner and his layers that look raphy, it is all too easy team have calculated that the layer, now just identical to the to miss evidence that 3–5 centimetres thick, was originally a metre or naked eye. the grains or chunks so deep. Their first assumption, based on similar of burnt wood found findings in other locations, was that the area had in a particular layer actually originated else- been used as an animal enclosure. But an analy- where, making them useless for dating neigh- sis of the phytoliths showed that they all came bouring samples. And if the carbon sample from domesticated grasses. Because the dung of removed for analysis actually contains material grazing animals would be expected to contain a from more than one source, it can throw the high proportion of wild plants, it seems possible dating off completely. that the phytoliths are evidence that animal fod- Having scientists on site can help archaeolo- der or grains were stockpiled at the site. gists to make faster decisions about where to Experts in radiocarbon dating, who usually excavate and what samples to collect, and, ulti- stick close to their laboratories, are also getting mately, yield more useful analyses. “Scientists their hands dirty. Elisabetta Boaretto, a nuclear in the field may come up with different ques- physicist at the Weizmann Institute, is a regular tions than archaeologists,” says archaeologist participant in digs, where she can be seen on Joseph Maran at the University of Heidelberg, her hands and knees scraping up samples with Germany, who specializes in ancient Greek the rest of the team. “I’m one of the few, if not sites. “It’s different from having an archae- the only one, in my field who’s down in the pits ologist define the question and then call in a digging,” she says. “But it’s essential.” scientist to address that specific issue.” While digging in the southeastern area of Maran says that the practice of having sci- zman T Tel Megiddo, Boaretto’s PhD student Michael entists actually excavating with archaeologists

H. Wa H. Toffolo unearthed a pottery storage jar full of is, to the best of his knowledge, a uniquely Israeli phenomenon. As a small country rich in archaeological sites and with a strong science base, it may be much easier for Israel’s scientists to spend extended periods at excavations than for those in other countries, he says. But Weiner hopes that the collaborative approach will catch on elsewhere. Earlier this year, he published a book, Microarchaeology: Beyond the Visible Archaeological Record, about the union of archaeology and analytical science, which he hopes will inspire other digs. In the past, few scientists have been willing to spend a large amount of time in the field, Weiner says. The key to making the collaboration work, he says, is “matching the right analytical tool to the challenge of revealing A portable spectrometer allows researchers to the microscopic record without slowing the get a fuller picture of their samples during a dig. excavation down enormously”. ■