An Amazonian tribe has been discovered that has no concept of time or dates, scientists have said.
Professor Chris Sinha, of the University of Portsmouth, led the research which found that the Amondawa people of Brazil do not even have words for "time", "week", "month" or "year".
In his study, published in the journal Language and Cognition, he argues that it is the first time scientists have been able to prove time is not a deeply entrenched universal human concept, as previously thought.
Prof Sinha said: "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. Instead, they change their names to reflect their life stage and position within their society. For example a little child will give up their name to a newborn sibling and take on a new one.
Prof 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."
First contacted by the outside world in 1986, 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.