Few records date that far back. Of course that doesn't stop many from making claims, but that's where the genealogists come by their duty to demand credible documents. Evaluating documents is tricky business. Sometimes it requires a bit of backbone on the part of genealogists who must question the work of others, often a beloved aunt or uncle. Many accept on faith whatever connections family genealogists have made.
Faith has little place in genealogy.
Documentation is the stan dard - birth certificates, marriage records, death certificates, obituaries, wills, deeds, passports and census records. These and many other documents are the foundation of genealogical research. Recently, someone told me they were confident of a family tree they'd unearthed because it connected to royalty. Coward that I am, I bit my tongue. When you stop and think about it, there's more cause to suspect and check out connections to royalty than probably any other type of connection.