Although it would seem logical that an older genealogy would always be less valuable than a newer one, as we would assume that the author of the newer work had access to more and better resources and modern genealogical methodology, that is not always so.
The biggest advantage that really old genealogies have is the author’s personal and family knowledge. If the genealogy was published in 1857 by an author who was born in 1800 and contains information on his immediate family in his lifetime, one could have more confidence that he knew what he was writing about.
Typically, information from extended family was collected through written correspondence, although rarely do these old genealogies identify exactly who reported what. In some cases a genealogist’s papers may be preserved in a library archive – NEHGS has a wide collection – and a researcher might be able to find the original letter or other source, which I have done. If not, then one needs to consider when the event took place in relation to the author’s lifetime. Were there older living relatives who could have passed on information from their own lifetimes first hand? That doesn’t, of course, mean the author got her information from such relatives, but she “could have.” It also, of course, doesn’t mean the relatives remembered correctly.
“Methodology” is the fancy term used to describe the methods used in researching a genealogy.
An old genealogy may have been carefully researched even if it lacks citations to sources. If wills or deeds are abstracted or at least mentioned, then there is a likelihood that the author accessed the originals. More detail usually indicates more complete research – quotes from an obituary giving locations, occupations, and relatives, for example, rather than just “Joe moved West.”
On the other end of the stick, while newer genealogies should be expected to improve on the old ones, a strange phenomenon appears instead. Authors are still copying the first several generations out of the old book, often verbatim and without critical analysis, because the old books are “there,” and the author is not versed in modern methodology and usually more concerned with identifying hundreds of descendants who did not make it into the first book.
“Methodology” is the fancy term used to describe the methods used in researching a genealogy. Researchers gathering information for their own publications today need to fully understand modern definitions of “proof” and how to apply standards to everything that they include in their own books. Otherwise you are just “passing” the old stuff forward and probably not being helpful. If you are serious about your contribution to family history, here are two more books you should have on your bookshelves:
Thomas W. Jones, Mastering Genealogical Proof, National Genealogical Society Special Topics Series Number 107 (Arlington, Va., 2013), available from the NGS store.
Robert Charles Anderson, FASG, Elements of Genealogical Analysis, How to Maximize Your Research Using the Great Migration Study Project Method (e-book edition also available), at the NEHGS online store.
While you are shopping, check both stores for many more useful works – perhaps a list of suggestions for your birthday and holiday gifts from the family?