Documentation in Genealogy

L. David Roper (

One often reads comments that one must have a document to support every purported fact in genealogy. That is an impossible feat and it is not correct. I will argue herein that documents are very often wrong about some facts and that consistency and logic applied to facts is as important as having documents. Finally, I will conclude that the ultimate documents about genetic connections are the DNA of the persons to be connected.

Types of documentation in genealogy

Genealogy is not a science! Imperfect documents, as almost all documents are, are not the holy grail of truth in genealogy. Documents must be combined with consistency and logic to arrive at the best approximations of genealogical truth.

There are many kinds of documents that are used in genealogy. Such documents often have dates, names, places and events errors. Sometimes those "errors" are purposeful by the persons who provided the information for the documents.

Some of the types of documents are:

Choosing Between Contradictory Documents

Given that any two documents are often contradictory about one or more events, how does one decide which document to believe? Here is the most logical way to procede:

Compare the contradictory "facts" of the two documents with the "facts" as already recorded from many other documents and make logical consistency judgements about which document is more likely to be correct. (Some times previous documents are judged to be more correct than the two new documents.) If such a judgement appears impossible, list both facts as possible facts. This is an iterative process: as new documents are discovered, their consistency with all other relevant documents must be judged in deciding what is the best approximation of the truth. One must always be open to the possibility of a document being incorrect about some of its "facts."

Using Consistency of Collected Data

Look not only at a new document, but also at the huge bulk of data that has been collected (by using data from many other documents) that impinge on the facts of the new document. A good genealogical program has various tools to aid in this process. For example, in a large genealogical data base, a given person may occur more than once; a search on names can reveal this and often allow connections to be made for which the documents disagree or do not even show. Thus, the entire data base serves as the "document," not a specific piece of paper or electronically recorded fact.

I have had much experience at using such data consistency in physics (Search for "Roper Resonance" using any Internet search engine.) Applying similar data-consistency techniques in genealogy has been very fruitful.

Genetic Testing as the Ultimate "Document"

Genealogy is a term that means genetic connections of many people. The ultimate arbiter of genetic connections is DNA. I have been using Y-chromosome testing for male lines in genealogy for since July 2001. (Unfortunately, mtDNA testing for female lines is not very helpful in genealgy. However, there are instances where it can be helpful; see Benjamin Franklin's DNA)

I have had many cases where apparently excellent paper documentation disagreed with the Y tests. Using the data I had collected before the Y tests, I have been able to make connections between families that no paper documentation can do.

In the near future full chromosomal DNA testing will become affordable, greatly expanding the possible use of DNA in genealogy.

Of course, DNA testing is not absolutely perfect. Mistakes can be made in the testing and in reporting the results of the testing. But such mistakes can be kept very small in number by vigilance.

Ultimate Truth in Genealogy

There is no such thing! One gets much closer to it using DNA than using imperfect documents and data consistency, but it will never be achieved.

Finally, I should mention that I am not interested in providing documentation for persons to join some social organization. I am only interested in getting as close to the truth as possible with regard to genetic connections.