While agro-pastoralism has been introduced in northern Europe – southern Scandinavia from 4000 BC, a hunting and gathering culture – the Pitted Ware (3300–2300 BC) – reappeared in this Neolithic context and left a central question: why it did not adopt agriculture despite contacts during one millennium with its neighbouring farming communities? We provide an explanation based on an economic mechanism related to trade between foragers and farmers. We demonstrate that the terms of trade of raw materials (mainly seal oil) extracted and sold by foragers have a tendency to decline in the long term in relation to the resources produced and sold by farmers. Neolithisation of northern Europe can therefore be viewed as the outcome of a long-term process based on trade in which hunter–gatherers get voluntarily involved without forecasting that it will, in the end, constraint most of them to give up their way of life.