  An active line of research has used on-line data to study the ways in which
discrete units of information---including messages, photos, product
recommendations, group invitations---spread through social networks. There is
relatively little understanding, however, of how on-line data might help in
studying the diffusion of more complex {\em practices}---roughly, routines or
styles of work that are generally handed down from one person to another
through collaboration or mentorship. In this work, we propose a framework
together with a novel type of data analysis that seeks to study the spread of
such practices by tracking their syntactic signatures in large document
collections. Central to this framework is the notion of an "inheritance graph"
that represents how people pass the practice on to others through
collaboration. Our analysis of these inheritance graphs demonstrates that we
can trace a significant number of practices over long time-spans, and we show
that the structure of these graphs can help in predicting the longevity of
collaborations within a field, as well as the fitness of the practices
themselves.
