One does not need to track a surname too far back in time to find that it frequently becomes unimportant, or at least ambiguous. If the surname you track is Swedish, you find that in the "old country" the surname changed with each generation. If you are a Johnson, its probably because it was John's son who got up the courage to leave Sweden for America. If he had stayed in Sweden, his son's last name would not have been Johnson, unless the father was named John Johnson. Some Swedes even ended up with un-Swedish sounding names while living in Sweden. In these cases, its a good clue that an ancestor probably served in the Swedish army and was arbitrarily given a new surname to simply make record keeping easier.
In one of my ancestral lines, the Williamson family added a slightly different twist. The surname of these Swedes that left in 1850 who were destined to become my ancestors was actually Olofson (Olson).This is the name shown on the ship's passenger manifest when it arrived in New York harbor. The Williamson family of Wataga actually didn't become Williamson until after they arrived in Illinois. After the death of the father from a chronic illness, the eldest son took over the paternal responsibilities for the family. In response, the family took the name "Williamson" honoring the surrogate father, the eldest son, i.e. William Olofson (Olson). In such a situation, the surname "Williamson" becomes relatively insignificant. Instead, it is the history of those bloodline that becomes important.
Probably a more common example of the surname gone astray is the impact of illiteracy in early America. Our ancestors knew their names, but many could neither read nor write. An "X", with a notation "his mark" is not at all uncommon in Civil War records. As a result, brothers and sisters, parents and children, often had different spellings for names that sound the same, depending upon the whim and the amount of education of the scribe that was recording the name. After all, if you can' t read, one spelling looks about as good as another. "Hogan" can be found as Hoggin, Hogin, and Hoggan. Many of these surname variations may come from a relatively recent common ancestor. Another example I found was on my "wife's side." There is a Pate surname that while in Virginia in the early 1700's was also written as Payte, and Paite, all relating to the same bloodline.
Another common event was the taking of new names on coming to American In some cases, it was simply converting the name literally to English. The surname "Greathouse" appearing to be most likely English, turned out to be German. Greathouse was 'Groethausen" when it left Germany in the early 1700s and first settled in Pennsylvania.
A more difficult situation occurred when the new arrivals either adopted or were given new surnames that had no real connection with the name that they left the old country with. This can really foul up the family tree. I suspect that it has brought many genealogical searches to a dead end.
For blacks in America, many of the surnames were simply those of the former owner. This often was apparently an action of convenience and reflected no bloodline relationship. In other cases, it can be inferred that there may have been bloodline relationships that accompanied the surname use. Looking at Kentucky census records following the end of the Civil War, I encountered several examples of same surname in adjacent or nearby dwellings. Beyond the black or white category on the census records that might suggest former slaves continuing to live nearby their former owners, the records also show mulattos. In one specific case there was a elderly white male head of household having substantial property. Living in a nearby dwelling was a younger, married mulatto male, having little property, but carrying the same first and last name of his wealthier, white neighbor. Although this is not conclusive evidence, it is certainly suggestive.
After a while, the obvious becomes apparent- the name is merely a label. Of course, this is precisely what names were. Surnames evolved from applied tags to distinguish one individual from another as the population in an area grew . This may have been done to accommodate business or gossip or both. Surnames sometimes were based on vocation, location, or kinship.
The bottom line for the genealogist: If your surname is "Rose" also search "Rowes." and "Rows" as spellings tended to evolve in early America. After all, "...a rose by any other name..."
*from William Shakespeare's Romeo and Juliet