Published in The Hindu on April 3, 2012
Latest evidence indicates that humans may have used fire as early as one million years ago. This is about 3 lakh years earlier than previously suggested by other studies. The ability to control fire was a turning point in human evolution.
The results published today (April 3) in the Proceedings of National Academy of Sciences are based on studies conducted on burned sediments and bone fragments collected from the Wonderwerk Cave in Northern Cape province, South Africa. The team was led by researchers from the University of Toronto and Hebrew University.
Excellent preservation of plant ash material and angular-shaped bone fragments provide unequivocal evidence that these were not transported to the cave either by wind or water but deposited at the very place where the burning took place (in situ deposition).
The researchers used micromorphology and molecular analytical technique to study the samples. The latter technique is particularly “well suited for identifying heat-related transformation in materials of different nature such as clay minerals and bones.”
Analysis suggests that some of the bone fragments were heated up to 500 degree C. Bone fragments collected from another location in the cave show some degree of discolouration (black, grey, and white fragments) “indicative of bone mineral heated to more than 400 degree C.” This discolouration in the form of darkening is typical of “charring and calcinations” caused by burning. About 47 per cent of bones and teeth samples show such discolouration.
The researchers found that the bones did not show complete removal of the carbonates. This indicates that the temperatures did not exceed 700 degree C. However, the clay minerals sticking to some of the grey bone fragments suggest that they were heated to temperatures ranging between 400 and 700 degree C. This “again supports the hypothesis of in situ burning of sediments during the Acheulean in this are of the cave,” the authors write.
The temperature measurements indicate that leaves, bushes and grass would have been used as fuel. The likelihood of repeated wildfires is “minimised” as the entire stratum of the deposit, which contained the plant ash, and burned bone fragments and sediments, show evidence of combustion.