British researchers have discovered an Amazonian tribe that has no concept of time or dates.
The Amowanda people of Brazil do not even have words for 'time', 'week', 'month' or 'year', said Chris Sinha of the University of Portsmouth.
He argues that it is the first time scientists have been able to prove that time is not a deeply entrenched universal human concept.
The professor reported his findings in the Journal of Language and Cognition, writing: 'For the Amondawa, time does not exist in the same way as it does for us.
'We can now say without doubt that there is at least one language and culture which does not have a concept of time as something that can be measured, counted or talked about in the abstract.
'This doesn't mean that the Amondawa are "people outside time", but they live in a world of events, rather than seeing events as being embedded in time.'
Team members, including linguist Wany Sampaio and anthropologist Vera da Silva Sinha, spent eight weeks with the Amondawa researching how their language conveys concepts like 'next week' or 'last year'.
There were no words for such concepts, only divisions of day and night and rainy and dry seasons. They also found nobody in the community had an age.
For example, a little child will give up their name to a newborn sibling and take on a new one.
Professor Sinha said: 'We have so many metaphors for time and its passing - we think of time as a "thing" - we say "the weekend is nearly gone", "she's coming up to her exams", "I haven't got the time", and so on, and we think such statements are objective, but they aren't.
'We've created these metaphors and they have become the way we think.
'The Amondawa don't talk like this and don't think like this, unless they learn another language.
'For these fortunate people time isn't money, they aren't racing against the clock to complete anything, and nobody is discussing next week or next year; they don't even have words for "week", "month" or "year".
'You could say they enjoy a certain freedom.'
The Amondawa continue their traditional way of life, hunting, fishing and growing crops.
But now, along with modern trappings such as electricity and television, they have gained the Portuguese language, putting their own language under threat of extinction.
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