Beginning with William & Annester, our ancestors were like many of that period and were illiterate. The written language prior to 1830 was primarily phonetically based. The U.S. did not establish a formal and approved form of writing the English language until the 1820/30 period where it was taught in school. This meant that our ancestors relied on the scribes interpretation of their spoken language. This reliance resulted in a multitude of spellings of our surname.
Our Y-DNA points to our Celtic roots and is believed to be indigenous to the British Isles and primarily Scotland. It is found in small segments in Ireland and Wales. The early Celtic clan consisted of a people of the period before and after the last glacier maximum moving across and settling in Iberia which is the area now known as Spain, Portugal, and other areas. Members migrated to various areas and our particular line appears to have continued on to a land mass that later became cut off from the main body of land and is now known as the United Kingdom.
Recently, those male descendants of William & Annester who tested Y-DNA, matched a "McGowan" whose relatives are from Scotland, having been there for a long time. The period of time to most recent common ancestor between those from our family who tested and this McGowan seems to strongly suggest that our own surname was most likely "McGowan" at one time and must have dropped the "Mc" over time.
The illiteracy of our ancestors has made it difficult for us to navigate through those who are not related to us but carry a variant of the surname. It has also created challenges within our family line research because of the need to follow the many variants. Today, the ancestors of William & Annester have maintained a few of these variants. This means that you may run into someone with one of the variants and not think you are related!
Because our Y-DNA is somewhat rare, it may be challenging to find a variant of our surname that currently lives in the U.K. or in Ireland or Wales. The desire to find your roots and participate in Y-DNA or DNA research is not as strong as it is in the U.S. Although it does occur, they are less likely to provide Y-DNA. If you already have a rare Y-DNA and need a larger sample size to participate in order to find the few who may match, it doesn't bode well for us at the moment. The "McGowan" person who matched us distantly is our first opportunity and the ability to match others may take years.
So, when you are trying to decide which surname spelling to apply to our ancestors, just know that they probably carried one of 6-8 different variants at one time or another and often even within the same legal document! Regardless of your surname variant today or your choice for assignment to your ancestor in the past, we are all related and should be proud of our heritage.