London, Dec 2 (ANI): Archaeological evidence has shown that Peruvian foraging societies were already chewing coca leaves 8,000 years ago.
Ruins beneath house floors in the northwestern Peru showed evidence of chewed coca and calcium-rich rocks.
Such rocks would have been burned to create lime, chewed with coca to release more of its active chemicals.
An international team said the discovery pushed back the first known coca use by at least 3,000 years.
Coca leaves contain a range of chemical compounds known as alkaloids. In modern times, the most notable among them is cocaine, extracted and purified by complex chemical means.
But the chewing of coca leaves for medicinal purposes has long been known to be a pastime at least as old as the Inca civilisation.
Other alkaloids within the leaves have mildly stimulating effects, can reduce hunger and aid digestion, and can mitigate the effects of high-altitude, low-oxygen environments.
Evidence of the chewing of the leaves has been found from around 3,000 years ago, but the addition of calcium-rich substances - which draw out far more of the alkaloids - was seen to be a much more recent development.
Now, Tom Dillehay of Vanderbilt University in the US and his colleagues have discovered evidence both of chewed leaves and calcium-rich rocks that were burned and scraped to supply ash for chewing.
The evidence was found beneath the buried floors of the homes of foraging peoples from northwestern Peru, where the conditions were favourable to preserve what is normally a fleeting, organic remnant of a bygone civilisation.
The samples were dated to about 8,000 years, but Dr Dillehay said that a further surprise was the distribution of the finds.
"We found it not so much in a household context, as if it was something that was heavily used by a lot of people, but rather... restricted to certain households of individuals and produced in a sort of public context - not individualised," the BBC quoted him as saying.
"The evidence we have suggests that unlike in Western societies - where if you've got the economic means you can have access to medicinal plants - that seems not to be the case back then," he added.
The study appears in the journal Antiquity. (ANI)