To any long term resident of the country, the fact of striking social change, both planned and unplanned, in Nepal is as obvious as a drive through the Kathmandu Valley or a walk through nearly any village. New roads, the extension of electric power, the building of factories and schools are the concrete manifestations of the Nepali government's development efforts since the end of the Rana era. Striking as these changes are, equally pervasive transformations have come to characterise the lives of Nepali people and these too, are easy to discover with a minimum of questioning. One finds increasing participation in wage labour work and in the mobility of village residents as they take advantage of new opportunities in the labour market for example. All of these trends have been widely documented for Nepal at both community and national levels. Less evident are the implications of these kinds of change for the relations between people and the social networks by which Nepalis have historically organised their lives. Increased schooling, certain forms of wage labour participation, and physical mobility are sometimes uncritically taken to be universal social goods. Yet these new activities are likely to have profound impacts on the historical practices which have proved adaptive for Nepali communities located in some of the world's toughest environments. Identifying and understanding these impacts are an essential element of sound development planning. In this paper, the authors try to analyse change in family-organised cooperative behaviours among the Tamang of a single Nepali village. They focus on the practice of husbands providing labour services to their wives' families after marriage. Such services have historically characterised a wide range of distinct ethnic groups in the Himalaya, notably but not solely those classified as Tibeto-Burman. As important components of social support networks, their transformation in response to the social changes mentioned above is an element of the future well-being of Nepal's people. The authors' analysis begins with the social theory that draws attention to these processes and relationships, but quickly moves into the empirical case of Timling in the upper Ankhu Khola. They discuss some of the implications of this analysis in their concluding remarks.