Original vs. Derivative Sources

 

Original vs. Derivative Sources: Why It Matters

You find your ancestor's birth date in a published county history book from 1910. You find the same birth date on the original church baptismal register from 1847. Both say the same thing. Both are sources. But they are not equal — and understanding why can save you from building your research on a foundation that crumbles.

What Makes a Source Original?

An original source is the first recording of a piece of information. The church register where the priest wrote the baptismal entry on the day of the ceremony is an original source. The census form the enumerator filled out as he stood on the doorstep is an original source. The will the testator signed in front of witnesses is an original source.

The defining characteristic of an original source is that it was created at the time and place of the event it records, or as close to it as the process allowed. Nobody copied it from somewhere else. It is the starting point — the first place the information was written down.

What Makes a Source Derivative?

A derivative source is anything created from an original source — a copy, a transcription, an abstract, an index, or a compilation. The county history book that published baptismal records was compiled decades later from the original registers. The Ancestry.com index entry for a census record was created by a modern indexer reading a digital image of a microfilm copy of the original census form. Each step in that chain introduces the possibility of error.

This does not mean derivative sources are useless. They are often how you find records in the first place — you search an index, find a name, and then go look at the original. The problem arises when you treat the derivative as though it were the original and never check.

Every time information is copied, transcribed, abstracted, or indexed, errors can be introduced. A derivative source is only as good as the person who created it — and even careful copyists make mistakes. Always go back to the original when you can.

The Chain of Copying

Consider what happens between a census record and the search result you see on Ancestry.com. The enumerator wrote the information on a paper form in 1880. That form was stored in Washington. Decades later, it was microfilmed — a photograph of the original. That microfilm was later digitised — a scan of the photograph. Then an indexer looked at the digital image and typed what they thought they saw into a database. You search that database and find your ancestor.

At every stage, something can go wrong. The microfilm might be blurry. The digital scan might be dark. The indexer might misread the handwriting. Your ancestor might be indexed as "Murply" instead of "Murphy" or "Jno." might not be recognised as "John." The search result is a derivative of a derivative of a derivative. If you accept the index entry without looking at the image, you may be accepting an error.

When the Original No Longer Exists

Sometimes the original source has been destroyed and only derivatives survive. The 1890 census was largely destroyed by fire — but some information from it survives in transcriptions, abstracts, and published extracts made before the fire. Many colonial church registers have been lost, but published transcriptions survive in genealogical society journals.

In these cases, the derivative is the best you have, and you use it — but you note in your citation that it is a derivative. You acknowledge that errors may have been introduced in the copying process. And you look for other sources that can corroborate the information independently.

Rule of thumbIf you can view the original or a direct image of it (photograph, scan, microfilm), do so. If you can only find a transcription, abstract, or index, use it as a finding aid to locate the original — and note in your citation that you are working from a derivative source if you cannot access the original.

Images Are Not Always Originals

A common misunderstanding is that looking at a digital image means you are looking at the original. You are not. You are looking at a photograph of the original. In most cases, this is close enough — a clear image of a census page is essentially as good as holding the original. But images can be cropped, misfiled, or out of focus. Pages can be missing from a microfilm roll. An image labelled as page 14 might actually be page 15 because of a scanning error.

The practical lesson: when you cite a source, be specific about what you actually looked at. Did you look at the original document in a courthouse? Did you look at a digital image on Ancestry? Did you look at a transcription in a published book? Your citation should reflect exactly what you consulted, so that someone following your research knows what they are working from.