How do ancestry websites work? Is it even possible to link back generations like that?

[sillyanswer592]

Ancestry websites work by people, such as yourself, submitting their family tree and by searchers photocopying public records and putting those on the site.

That's it: public records that have been copied and family trees that people upload.

Whether ancestry.com, the Mormons, or whomever, no effort is made to determine the validity of the trees or records.

But, of course, there is no way to determine the validity of the records; which is strange in itself, as people always assume that public records are 100% accurate. They aren't, but what can you do? That is why so many claim that no one can actually trace their ancestry even 200 years; public records are not accurate, and 10% - 20% of births are illegitimate.

As to how generations are linked, it is the same as when you say, "These are my parents". That's it: you know your parents, your parents knew their parents, and so on. Then someone puts in on the web.