Copying is not research. That is why we have sources. We have sources with our records so we can tell if what we are looking at is reliable. But we also have sources so we can see where the information came from. Take my Tanner family as an example. There are a series of surname books dating back to the 1800s that talk about my ancestors. Guess what? Everything after the original books is nothing more than a copy of the previous books. Do you think any one of the authors would have thought to include a source or attribution? It did not happen. At the beginning of the first book in the series, the author mentions searching records in Rhode Island and names a few records, but none of the information in the book is cited to any particular source. Later authors omitted the references to the Rhode Island records entirely.
But I digress. The issue this post addresses is the concept of what is genealogical research and are there limits? If I find a marvelous book published about one of the people or lines in my pedigree, shouldn't I just copy the information and consider that line done? Do I as a genealogist have any obligation, moral or otherwise, to reasonably verify information that has no sources listed? If there are sources listed, do I have any obligation to make sure the sources are valid? So, what if I find a book like Gatfield, George. Guide to Printed Books and Manuscripts Relating to English and Foreign Heraldry and Genealogy; Being a Classified Catalogue of Works of Those Branches of Literature. London: Mitchell and Hughes, 1892 and through that source, I find a book on my surname published back in the 1800s. Wait, I think a quote from Donald Lines Jacobus is appropriate, "In a field where professional genealogists so often show their ineptitude, the amateur is a lost lamb. In fact, amateurs are responsible for many of the erroneous royal lines that have appeared in print; and once they have originated, they have been copied and reprinted by the type of professional incompetent who believes that the printed word can never lie."
It is my opinion, whatever that is worth, that genealogy without verified sources is nothing more than fiction in pedigree format. Do I have to verify my parents' birth dates? Am I to doubt my own origins? Do you have any idea how many people find that the dates given for near ancestors, including parents, are wrongly recorded? I have two different dates for my parents' wedding? Which is correct? What if I have documents showing both dates?
If dates in close proximity can be erroneous, then how much more should we doubt those going back into antiquity? Let's get a definition going here. A brick wall in genealogy is the inability to establish a relationship, name or date where records should and can exist. A genealogical limit is the inability to continue research because of lack of any records at all or at a time before records became available. If you would like to read an interesting perspective on extending lines back into the past, published 8 August 2010 by Martin Hollick, the Slovak Yankee, read Royal Lines, Medieval Genealogy and Ancient Lineages.
So let's discuss a little more about the availability of records. The Patroligia Latina is an enormous collection of the writings ecclesiastical writers published by Jacques-Paul Migne between 1844 and 1855. In that book, which is essentially a bibliography, there is a demonstrated decline in the number of extant volumes in the collection in the 7th, 8th and 10th centuries. In other words, very few manuscripts were written during that time period. Those that do exist have been mostly exhaustively studied. See Wikipedia. So by about the 10th Century, you will begin to run out, not only of genealogy, but books altogether.
Let me repeat, I am not discussing whether or not you or anyone else can prove a royal lineage. I do not doubt that a great deal of competent history has gone into research a few of these lines, but my question is, do you accept that research or is there some obligation to verify your own lines? And if there is an obligation, how far back can you practically go? By the way, if you interested in answering questions on royal lines, try looking for books on royal lines in the Family History Archives. They have digitized many of the early books on that subject online.
Genealogy is really history and history has its limits. A real lack of sources, not an inability to find what is there, imposes a practical end to research. There are few people who are willing to spend the time and effort necessary to become competent researchers in very old records. Very long an ancient pedigrees are possible but are hardly unique and have a high degree of uncertainty. Copying a royal line or any ancestral line you find in a book without doing your own independent research to verify sources, may be personally satisfying but is hardly believable and not genealogy.