The demographic history of Scotland includes all aspects of population history in what is now Scotland. 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 extent of woodland indicates that the Roman invasions from the first century AD had a negative impact on the native population.

There are almost no written sources from which to reconstruct the demography of early medieval Scotland. This was probably a high fertility, high mortality society, similar to developing countries in the modern world. The population may have grown from half a million to a million by the mid-fourteenth century when the Black Death reached the country. It may then have fallen to as low as half a million by the end of the fifteenth century. Roughly half lived north of the River Tay and perhaps 10 per cent in the burghs that grew up in the later medieval period. Inflation in prices, indicating greater demand, suggests that the population continued to grow until the late sixteenth century, when it probably levelled off. It began to grow again in the relative stability of the late seventeenth century. The earliest reliable evidence suggests a population of 1.2 million in 1681. This was probably reduced by the "seven ill years" of the 1690s, which caused severe famine and depopulation, particularly in the north. The first national census was conducted in 1755, and showed the population of Scotland as 1,265,380. By then four towns had populations of over 10,000, with the capital, Edinburgh, the largest with 57,000 inhabitants.

Overall the population of Scotland grew rapidly in the late eighteenth and nineteenth centuries. Whilst the Lowland Clearances caused depopulation in the affected areas, only local net population reductions occurred in the Highlands during the Highland Clearances. By 1801, Scotland's population had reached 1,608,420 and it grew to 2,889,000 in 1851 and 4,472,000 in 1901. By the beginning of the twentieth century, one in three lived in the four cities of Glasgow, Edinburgh, Dundee and Aberdeen. Glasgow emerged as the largest city, with a population of 762,000 by 1901, making it "the Second City of the Empire". Despite industrial expansion there were insufficient jobs and between the mid-nineteenth century and the Great Depression from 1929-39 about two million Scots emigrated to North America and Australia, and another 750,000 to England. The Scots were only 10 per cent of the British population but they provided 15 per cent of the national armed forces, and eventually accounted for 20 per cent of the dead in World War I (1914–18). With the end of mass migration, the population reached a peak of 5,240,800 in 1974. Thereafter it began to fall slowly, moving down to 5,062,940 in 2000. There was also a decrease in some urban populations as a result of policies of slum clearance, overspill and relocation to new towns, with the population of Glasgow falling from over one million in 1951 to 629,000 in 2001. Rural areas also saw a loss of population, particularly in the Highlands and Hebrides islands.

Prehistoric and Roman eras

At times during the last interglacial period (130,000– 70,000 BC) Europe had a climate warmer than today's, and early humans may have made their way to what is now Scotland, though archaeologists have found no traces of this. Glaciers then scoured their way across most of Britain, and only after the ice retreated did Scotland again become habitable, around 9600 BC.F. Pryor, Britain B.C.: Life in Britain and Ireland before the Romans (London: Harper Collins, 2003), , p. 99. Mesolithic hunter-gatherer encampments formed the first known settlements, and archaeologists have dated a site near Biggar to around 8500 BC. Numerous other sites found around Scotland build up a picture of highly mobile boat-using people making tools from bone, stone and antlers, probably with a very low density of population.P. J. Ashmore, Neolithic and Bronze Age Scotland: An Authoritative and Lively Account of an Enigmatic Period of Scottish Prehistory (London: Batsford, 2003), .

Neolithic farming brought permanent settlements, such as the stone house at Knap of Howar on Papa Westray dating from 3500 BC, and greater concentrations of population. Although the Roman geographer Ptolemy indicated that there were 19 "towns" in Caledonia, north of the Roman province of Britannia, no clear evidence of urban settlements has been found and these were probably hillforts.A. Moffat, Before Scotland: The Story of Scotland Before History (London: Thames and Hudson, 2005), , pp. 268–70. There is evidence of over 1,000 such forts, most south of the Clyde-Forth line, but the majority seem to have been abandoned in the Roman period.J-D. G. G. Lepage, British Fortifications Through the Reign of Richard III: An Illustrated History (McFarland, 2012), , pp. 25 and 31. There is also evidence of distinctive stone wheelhouses (a type of roundhouse, with a circle of stone piers resembling the spokes of a wheel)I. Crawford, "The wheelhouse" in B. B. Smith and I. Banks, eds, In the Shadow of the Brochs (Stroud: Tempus, 2002), , pp. 127–28. and over 400 small underground souterrains (underground galleries that may have been used to store food).R. Miket, "The souterrains of Skye" in B. B. Smith and I. Banks, eds, In the Shadow of the Brochs (Stroud: Tempus, 2002), , pp. 77–110. Extensive analyses of Black Loch in Fife indicate that arable land spread at the expense of forest from about 2000 BCuntil the time of the Roman advance into lowland Scotland in the first century AD, suggesting an expanding settled population. Thereafter, there was regrowth of birch, oak and hazel for some 500 years, suggesting that the Roman invasions had a negative impact on the native population.T. C. Smout, R. MacDonald and F. Watson, A History of the Native Woodlands of Scotland 1500–1920 (Edinburgh: Edinburgh University Press, 2nd edn., 2007), , p. 34.

Middle Ages

There are almost no written sources from which to reconstruct the demography of early medieval Scotland. Estimates have been made of a population of 10,000 in Dál Riata and 80–100,000 for Pictland, which was probably the largest region.L. R. Laing, The Archaeology of Celtic Britain and Ireland, c. AD 400–1200 (Cambridge: Cambridge University Press, 2006), , pp. 21–2. It is likely that the fifth and sixth centuries saw higher mortality rates due to the appearance of bubonic plague, which may have reduced the population.P. Fouracre and R. McKitterick, eds, The New Cambridge Medieval History: c. 500-c. 700 (Cambridge: Cambridge University Press, 2005), , p. 234. The examination of burial sites for this period, such as that at Hallowhill, St Andrews, indicates a life expectancy at birth of only 26 to 29. The known conditions have been taken to suggest it was a high fertility, high mortality society, similar to developing countries in the modern world, with a relatively young demographic profile, and perhaps early childbearing, and large numbers of children born to each woman (although with high child mortality). This would have meant a relatively low ratio of available workers to the number of mouths to feed, which in turn would have made it difficult to produce a surplus that would allow demographic growth and the development of more complex societies.A. Woolf, From Pictland to Alba: 789 – 1070 (Edinburgh: Edinburgh University Press, 2007), , pp. 17–20.

From the formation of the Kingdom of Alba in the tenth century, to before the Black Death reached the country in 1349, estimates based on the amount of farmable land suggest that the population may have grown from half a million to a million.R. E. Tyson, "Population Patterns: 1. to 1770", in M. Lynch, ed., The Oxford Companion to Scottish History (New York, 2001), , pp. 487–9. Growth was probably punctuated by occasional crises, like the famines recorded in chronicles for 1154 and 1256. More significant was a series of poor harvests that affected Scotland and most of Europe in the early fourteenth century and widespread famines in 1315–16 and in the later 1330s.M. Lynch, Scotland: A New History (London: Pimlico, 1992), , p. 71.

Although there is no reliable documentation of the demographic impact of the Black Death in Scotland, there are some indications of the immediate effects of the plague. Walter Bower recorded that 24, about a third, of the canons of St. Andrews died during the outbreak.K. Jillings, Scotland's Black Death: The Foul Death of the English (Stroud: Tempus, 2007), , p. 95. There are also anecdotal references to abandoned land in the following decades. If the pattern followed that in England, then the population may have fallen to as low as half a million by the end of the fifteenth century.S. H. Rigby, ed., A Companion to Britain in the Later Middle Ages (Oxford: Wiley-Blackwell, 2003), , pp. 109–11. Compared with the distribution of population after the later Clearances and the Industrial Revolution, these numbers would have been relatively evenly spread over the kingdom, with roughly half living north of the River Tay.J. Wormald, Court, Kirk, and Community: Scotland, 1470–1625 (Edinburgh: Edinburgh University Press, 1991), , p. 61.

Early modern era

Price inflation, which generally reflects growing demand for food, suggests that the population was probably still expanding in the first half of the sixteenth century.R. Mitchison, A History of Scotland (London: Routledge, 3rd edn., 2002), , p. 145. Almost half the years in the second half of the sixteenth century saw local or national scarcity, necessitating the shipping of large quantities of grain from the Baltic. Distress was exacerbated by outbreaks of plague, with major epidemics in the periods 1584-8, 1595 and 1597–1609.Wormald, Court, Kirk, and Community, pp. 166–8. The population expansion probably levelled off after the famine of the 1590s, as prices were relatively stable in the early seventeenth century. Famine was common, with four periods of famine prices between 1620 and 1625. The invasions of the 1640s had a profound impact on the Scottish economy, with the destruction of crops and the disruption of markets resulting in some of the most rapid price rises of the century, but population probably expanded in the Lowlands in the period of stability that followed the Restoration in 1660.Mitchison, A History of Scotland, pp. 291–3. There is evidence that there was a different demographic regime operating in the Highlands, where growth probably continued from the early seventeenth century to the late eighteenth century.I. D. Whyte, "Population and mobility in early modern Scotland" in R. A. Houston and I. D. Whyte, eds, Scottish Society, 1500–1800 (Cambridge: Cambridge University Press, 2005), , p. 41.