All family lines eventually end even if you have one that "goes back to Adam" which, by the way, cannot be supported by any currently available contemporary sources. For some researchers, these end-of-line people beckon them like climbing Mt. Everest or going into Outer Space. Some of those who are beckoned end up obsessed with the goal. I regularly hear accounts from researchers about their efforts to find the elusive ancestor. Some researchers have spent years of effort and probably a significant amount of money pursuing their quixotic dream.
Here is an example of what I am talking about. This is a 5 generation fan chart of one of my ancestors.
Just as the total number of your ancestors increases exponentially, so does the available number of ends-of-lines. One thing you could learn from this rather simple fact is that pursuing any one of your end-of-line ancestors for a long time just means you are ignoring all of the others. If you finally break through and find the next generation, you have just added two more end-of-line situations.
But wait, it might be a good idea to think about why these end-of-line situations exist. Here is a list of possible reasons.
1. You have gotten so far back in time that you have run out of records.
2. You are looking for the wrong person in the wrong time period in the wrong place.
3. The recorded research in the more recent generations is faulty or inaccurate.
4. The end-of-line person was an orphan or a foundling and there is no record of his/her parents.
5. For some reason the person did not want to be found and the names, dates, or places have been changed or misrepresented.
Well, the list could go on but I hope you get the point. There is probably a good reason why the records for some people and almost all end-of-line people seem to evaporate.
Let's suppose that you are the first person in your family to start to record your genealogy and begin a family tree. You begin by entering your own personal information and then that of your immediate family including parents and grandparents. If you don't know the identity of your biological parents, they are your "end-of-line. There are no limitations on the people you can add as parents. They can be biological parents, step-parents, adopted parents, guardianship parents, in short, about any possible parental relationship that can exist. Of course, the nature of the relationship does not make the end-of-line people either appear or disappear. By the way, if you are missing parents or grandparents, you really should get one or more DNA tests on the major family tree programs, which will give you a chance at finding some relatives assuming you want to find your biological parents.
Now you could start calling the end-of-line ancestor a brick wall but that just describes your attitude, not the real question or issue. Some of my ancestors worked on specific family lines for years. I have accumulated genealogy that reflects more than a hundred years of research and notwithstanding the amount of time and energy that has gone into the research, two of my ancestral lines end in the sixth generation both in the 1700s. Breaking through that kind of an end-of-line can be satisfying but you need to be able to admit that there just are not enough records to find some people.
Over time, more and more records will be digitized and available online. Today, while doing some research on an end-of-line for a patron from the Brigham Young University Family History Library, I found a long list of documents that need to be researched to see if the information he needs is available. Unfortunately, many of those records are only available in the state where they are located far away from me. Given the pandemic and my inability to access the BYU Family History Library or even travel, my options are very limited. But over time, given the fact that these documents do exist, it is possible that future researchers will find time to review this same end-of-line and find a clue or even the entire solution to the challenge.