Fire: Home is where the hearth is

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  • Published: Feb 1, 2014
  • Author: David Bradley
  • Channels: Infrared Spectroscopy
thumbnail image: Fire: Home is where the hearth is

Rolling back the years

Humans began using fire probably around 1 billion years ago, but new infrared spectroscopic work by an Israeli team suggests that we built our first hearths to give us more control over fire about 300,000 years ago.

Humans began using fire probably around 1 million years ago, but new infrared spectroscopic work by an Israeli team suggests that we built our first hearths to give us more control over fire about 300,000 years ago. Infrared spectroscopy of grey sediments at the Qesem Cave, an archaeological site near present-day Rosh Ha'ayin in the Central District of Israel, have revealed the dominant material in those sediments to be calcite, the main mineral present in wood ash.

As a species, we probably used fire a million years ago. But, archaeologists suspect that our taming of fire, the time when we first sat around an open hearth, a campfire, if you will, was much more recent. When did we really begin to control fire and use it for our daily needs? It is a question central to understanding the advent of our species as a technological creature and is the subject of heated debate and online flame wars. Now, a team in Israel has pushed back the earliest "hearth" to a time around 300,000 years ago, the time humans were using the Qesem Cave. Their unequivocal evidence suggests repeated fire building over a continuous period at this site and hints at the people who lived here as having a highly advanced social structure and intellectual capacity.

A hearth act to follow

Excavations in Qesem Cave have been ongoing since 2000 with Avi Gopher and Ran Barkai of Tel Aviv University, Ruth Shahack-Gross of the Kimmel Center for Archeological Science at the Weizmann Institute of Science involved in research there since the beginning. Shahack-Gross's expertise lies in the identification of archaeological materials. She used IR spectroscopy to analyse samples of ash and identified not only wood ash but also bone that had been exposed to the very high temperatures one might measure in a large hearth. "My colleague and co-author, Francesco Berna of Simon Fraser University in Canada, conducted micro-FTIR analyses which supported the findings and added information on presence of burnt soil aggregates," Shahack-Gross told us.

Shahack-Gross has also tested the micro-morphology of the ash by extracting a cubic chunk of sediment from the hearth and hardening it in the lab. Thin slices under the microscope reveal unequivocal evidence for the presence of wood ash crystals as well as the processes that the samples had undergone and showed many layers, micro-strata, within, suggested that the same samples had been heated in the hearth repeatedly over time. The team published details of their findings in the Journal of Archaeological Science.

"Infrared spectroscopy and micro-spectroscopy of black and white-coloured bones, as well as clay minerals from soil aggregates, all associated with the ash - revealed the bones and clay minerals were burnt at temperatures well above 500 Celsius," Shahack-Gross told SpectroscopyNOW, important evidence that points to repeated use of a hearth.

Coming home to a real fire

Of course, additional evidence hinting at the increasing sophistication of the prehistoric cave users is the presence of a large number of flint tools that were apparently used for cutting meat. Other flint tools found a few metres had a different shape and presumably some other use. The presence of large numbers of burnt animal bones suggests that the cave users were not vegetarians and used the fire repeatedly to cook meat. Indeed, the evidence points strongly to this site being a "household" with clear demarcation between areas for particular activities. The cave may well have been a base camp to which the users returned again and again…their home one might suggest.

"These findings help us to fix an important turning point in the development of human culture – that in which humans first began to regularly use fire both for cooking meat and as a focal point – a sort of campfire – for social gatherings," she says. "They also tell us something about the impressive levels of social and cognitive development of humans living some 300,000 years ago." The researchers think that these findings, along with others, are signs of substantial changes in human behaviour and biology that commenced with the appearance in the region of new forms of culture - and indeed a new human species - about 400,000 years ago.
The illustration shows the contribution of micro-FTIR spectroscopy to the study: At top, one can see a scan of a micromorphology thin section with yellow, brown and black bone fragments embedded in sediment. The upper spectrum illustrates in black the spectrum of unheated clay minerals while in red is the spectrum of heated (dehydroxylated) clay. lower spectrum is of a burnt bone, indicated by the presence of absorbance bands at 628 and 1092 cm-1 (bands that do not appear in unburnt bone mineral).

Related Links

J Archeol Sci, 2014, online: "Evidence for the repeated use of a central hearth at Middle Pleistocene (300 ky ago) Qesem Cave, Israel"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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