I have a question: I am not sure how this works here – how can someone who is not related at all enhance my ancestors ? Even if it is open to the public.
Thank you very much.
Welcome to the "Community.FamilySearch' Forum.
I am just another 'lowly' User/Patron ...
You never know ...
Short Answer: In fact, they MAY actually be "Related" to you, somewhere along your "Ancestral" Lines.
Well, of course, they not actually be "Related" to you; but, that said, for whatever reason, they may just be "Working" (eg. on behalf of another User/Patron), somewhere along your "Ancestral" Lines.
There were just a couple of Users/Patrons, that both, my Wife; and, I, DID NOT recognise, the "Contact Name" of (ie. we had never seen them before, while working on our "Ancestral" Lines), when we check our Lists of "Highest Contributors"; but, only one or two - we knew most.
IF, a User/Patron, appears, on one's List, of "Highest Contributors"; THEN, for whatever reason, they WILL / MUST be "Working", somewhere along one's "Ancestral" Lines - that is for certain.
As an aside ...
They may even be, a NEW, (and, as of yet, "Unknown") "Extended" Family member (eg. Distant Relative) ...
IF, you like; THEN, send them a "Message', in "User Messaging", in 'FamilySearch', strike up a conversation ...
[or, NOT, the choice is yours ... ]
Nothing ventured, nothing gained ...
It could be the start of a wonderful "Collaboration" ...
Just my thoughts.
I hope that this helps/assists. somewhat.
The "how" of your question is easy to answer. FamilySearch Family Tree is a wiki-style, open edit database in which all users have equal access to all entries (except Private individuals and Read-Only individuals). The entire design is based on the philosophy of collaborative research and that any researcher should have equal ability to add or edit any record, with all the great advantages and potential horrors this implies.
To stress this vital difference between Family Tree and basically all other on-line family tree services: There is only one tree and we are all working together in the same tree.
"Even if it is open to the public" on Ancestry, My Heritage and such means the public can view it. "Even if it is open to the public" on FamilySearch means we take part in maintaining a section of the one, huge, tree that is Family Tree along with everyone else with any interest in that section.
The implied "and why would they?" in your question has probably as many reasons as there are researchers. I'll just mention three.
1) Collaborative Research
Many families have a designated or self-appointed family historian. Since Family Tree is collaborative, there is no reason for each person in a family to independently do all the research. Usually there are a couple of people in the family who are very interested in family history and become very skilled in genealogy that take over all the work in Family Tree while the others are just thrilled to not have to. For example, DHarolden might be the designated researcher for his nearest family and might be the sibling of the spouse of a cousin of yours. If DHaroldsen is doing all work in Family Tree under his or her own account, even all the work on his or her sibling's spouse's family, a relationship would not show since you are only related to your cousin, not your cousin's brother- or sister-in-law.
2) Erroneous Merge Prevention
Say, for example, you are related to Mary Smith, born 1889 in New York, DHaroldsen is related to Mary Smith, born 1889 in New York, I am related to Mary Smith, born 1889 in New York, and someone else is related to Mary Smith born 1889 in New York and that someone else, not us of course, merged these four different Mary Smith's into one person. DHaroldsen may have run across this mess and unmerged everyone then did enough research on all four of these Mary Smiths to add vital information, add sources, add additional family members, in short, done everything possible to make it so obvious that these are four different Mary Smiths that no one would ever merge them again. You would show no relationship to DHarold because you are related to your Mary Smith and he or she is related to his or her Mary Smith.
3) Cluster Research
My wife's father was born on an island on the west coast of Norway with a population in the 1900 census of 2,424. In order to make sure that we are not missing any of my wife's family, we are doing cluster research, which looks at all people surrounding a family to find connections and other family members. I am going through line by line in the parish register for that island creating or improving the Family Tree record for every single child born between 1878 and 1910. I use all the parish records, census records, and other resources to research and completely document in Family Tree each child, both parents, all siblings, all grandparents, and all aunts and uncles. I'm finding that about 90% of the time, by the time I get to the grandparents I have hooked into an existing collateral line for my wife and the child is between a 4th to 12th cousin of some remove.
The other 10% are not related to her but I do just as careful and extensive research for that 10% as well. I'm right there. I have the expertise. And the only way to show they are not related to my wife is to complete the research on the grandparents. However, occasionally when I have gotten all the information in on a child, a duplicate will pop up that will have just enough information to know it is definitely the same person but will only have sources for the person's life in America. Clearly whoever was working on his or her immigrant ancestor hit a road block and was not able to make the jump from the US to Norway. So I add emigration records and sufficient documentation to prove the two entries are the same and merge them, adding at least two generations or sometimes several more to the family line of someone my wife has no relationship to. I do it because I can and to help them out.