Division of labour in a society, and the corresponding tying down
 of individuals to a particular calling, develops itself, just as does the
 division of labour in manufacture, from opposite starting-points. Within
 a family, [26] and after further development within
 a tribe, there springs up naturally a division of labour, caused by differences
 of sex and age, a division that is consequently based on a purely physiological
 foundation, which division enlarges its materials by the expansion of the
 community, by the increase of population, and more especially, by the conflicts
 between different tribes, and the subjugation of one tribe by another.
 On the other hand, as I have before remarked, the exchange of products
 springs up at the points where different families, tribes, communities,
 come in contact; for, in the beginning of civilisation, it is not private
 individuals but families, tribes, &c., that meet on an independent
 footing. Different communities find different means of production, and
 different means of subsistence in their natural environment. Hence, their
 modes of production, and of living, and their products are different. It
 is this spontaneously developed difference which, when different communities
 come in contact, calls forth the mutual exchange of products, and the consequent
 gradual conversion of those products into commodities. Exchange does not
 create the differences between the spheres of production, but brings what
 are already different into relation, and thus converts them into more or
 less inter-dependent branches of the collective production of an enlarged
 society. In the latter case, the social division of labour arises from
 the exchange between spheres of production, that are originally distinct
 and independent of one another. In the former, where the physiological333
 division of labour is the starting-point, the particular organs of a compact
 whole grow loose, and break off, principally owing to the exchange of commodities
 with foreign communities, and then isolate themselves so far, that the
 sole bond, still connecting the various kinds of work, is the exchange
 of the products as commodities. In the one case, it is the making dependent
 what was before independent; in the other case, the making independent
 what was before dependent.