The Mathematics Genealogy Project is a vast family tree connecting mathematicians to their dissertation advisors, going back in some lines to the 15th century.   It can be a compelling toy- after I mentioned Georg Christoph Lichtenberg in a post Thursday, I looked up a math professor who works across the street from me and traced his lineage back to Lichtenberg.  That’s pretty easy to do- of about 130,000 mathematicians indexed, 23,522 are descendants of one or the other of Lichtenberg’s two advisees, Heinrich Brandes and Bernhard Thibault.  So you have about a 1/5 chance that any living mathematician you choose will be a descendant of Lichtenberg.  

I don’t know anything about how mathematics works as a field, but I do know enough of certain other fields to say that a reference tool like this would be of great value to them.  For example, the research careers of most classical scholars are largely defined by their dissertations, so it would be natural to sort classicists into families defined by dissertation advisor.  Efforts have been made to copy the Mathematics Genealogy Project in some other fields; here for example is “The Philosophy Family Tree.”