London, June 18 (IANS): Researchers have stumbled upon evidence of early prehistoric 'balanced' diet as well as the presence of respiratory irritants such as charcoal, during excavation of Qesem Cave in Israel.

The researchers from Tel Aviv University, in collaboration with scholars from Spain, England and Australia, have uncovered evidence of food entrapped in the dental plaque of 400,000-year-old teeth at Qesem Cave near Tel Aviv, the site of many major discoveries from the late Lower Palaeolithic period.

The research provides direct evidence of what early Palaeolithic people ate and the quality of the air they breathed inside Qesem Cave.

Possible respiratory irritants, including traces of charcoal - manmade environmental pollution - found in the dental calculus may have resulted from smoke inhalation from indoor fires used for roasting meat on a daily basis.

This earliest direct evidence for inhaled environmental pollution may well have had a damaging effect on the health of these early humans.

"This is the first evidence that world's first indoor BBQs had health-related consequences. People who lived in Qesem not only enjoyed the benefits of fire -- roasting their meat indoors -- but they also had to find a way of controlling the fire -- of living with it," said professor Ran Barkai from TAU.

"This is one of the first, if not the first, cases of manmade pollution on the planet. Progress has a price -- and we find possibly the first evidence of this at Qesem Cave 400,000 years ago."

The researchers also found minute traces of essential fatty acids, possibly from nuts or seeds and small particles of starch in the analysed calculus.

"We know that the cave dwellers ate animals and exploited them entirely. We know that they hunted them, butchered them, roasted them, broke their bones to extract their marrow and even used the butchered bones as hammers to shape flint tools," Barkai said.

"Now we have direct evidence of a tiny piece of the plant-based part of their diet, in addition to the animal meat and fat they consumed. We have come full circle in our understanding of their diet and hunting and gathering practices."

The study was published in the journal Quaternary International.