As mentioned, dance may have been one of the first ways that early people expressed themselves, perhaps dancing through the events of the day by some prehistoric fire in the evening. If so, then it seems that dance may be fundamental to social cohesion and one of the earliest examples of culture we have as a species. Archaeological evidence demonstrates that people have danced for at least 9,000 years and probably more. In written testimony, dancing was mentioned as far back as the times of Ancient Greek writers like Plato and Aristotle. As theatre began to take off, so movements became more formalised, leading to the classical forms of dance we are more familiar with today. Folk dancing appears to have developed entirely separately within communities, however.