T. M. Devine's definition of the term), whilst the "farming" south and east Highlands contained 121,224 people. Causes Agriculture in the Highlands had always been marginal, with famine a recurrent risk for pre-clearance communities. Nevertheless, population levels increased steadily through the 18th and early 19th centuries. This increase continued through nearly all of the time of the clearances, peaking in 1851, at around 300,000. Emigration was part of Highland history before and during the clearances, and reached its highest level after them. During the first phase of the clearances, emigration could be considered a form of resistance to the loss of status being imposed by a landlord's social engineering. Different landowners decided to introduce the improvements that required clearance at different times and for different reasons. The common drivers of clearance are as follows: Economic changes Replacement of the old-style peasant farming with a small number of well-capitalised sheep farmers allowed land to be let at much higher rents. It also had the advantage, for the landowner, that there were fewer tenants to collect rent from, thus reducing the administrative burden of the estate. In some areas, land remained in arable use after clearance but was farmed with more intensive modern methods. Some of the earliest clearances had been to introduce large-scale cattle production. Some later clearances replaced agriculture with sporting estates stocked with deer. There were instances of an estate being first cleared for sheep and later being cleared again for deer. The major transition, however, was to pastoral agriculture based on sheep. The most productive sheep were the Cheviot, allowing their owners to pay twice as much rent as if they had stocked with Blackfaces. The Cheviot's disadvantage was that it was less hardy and needed low-level land on which to overwinter. This was usually the old arable land of the evicted population, so the choice of sheep breed dictated the totality of clearance in any particular Highland location. Social engineering Some of those carrying out clearances believed that this was for the benefit of those affected. Patrick Sellar, the factor (agent) of the Countess of Sutherland, was descended from a paternal grandfather who had been a cottar in Banffshire and had been cleared by an improving landlord. For the Sellars, this initiated a process of upward mobility (Patrick Sellar was a lawyer and a graduate of Edinburgh University), which Sellar took to be a moral tale that