Their analysis revealed that the average human life is split up by four pivotal 'turning points' between five key stages - childhood, adolescence, adulthood, early ageing, and late ageing. If you're in your early 30s and still don't feel like a proper adult, you're not wrong, as scientists say the 'adolescent' period lasts until age 32. 'The brain goes through a natural transition around the time puberty begins, which extends until the early 30s,' lead researcher Dr Alexa Mousley told the Daily Mail. 'This age window exceeds what many consider "adolescence".'