The demographic history of Scotland includes all aspects of population history in what is now Scotland. Scotland may have been first occupied in the last interglacial period (130,000–70,000 BC), but the earliest surviving archaeological evidence of human settlement is of Mesolithic hunter-gatherer encampments. These suggest a highly mobile boat-using people, probably with a very low density of population. Neolithic farming brought permanent settlements dating from 3500 BC, and greater concentrations of population. Evidence of hillforts and other buildings suggest a growing settled population. Changes in the scale of woodland indicates that the Roman invasions from the first century AD had a negative impact on the native population.