  In this work, we introduce a quantitative methodology to define what is the
main trunk and what are the significant branches of a minimum spanning tree
(MST). We apply it to the pulsar tree, i.e. the MST of the pulsar population
constructed upon a Euclidean distance over the pulsar's intrinsic properties.
Our method makes use of the betweenness centrality estimator, as well as of
non-parametric tests to establish the distinct character of the defined
branches. Armed with these concepts, we study how the pulsar population has
evolved throughout history, and analyze how to judge whether a new class of
pulsars appears in new data, future surveys, or new incarnations of pulsar
catalogs.
