Original sentence: This has led to much speculation on less widely-respected theories such as that the tribe of Dan were the Danes, or the Tuatha Dé Danann of Ireland, based on the principle that the word Don and Dan appears in many names of rivers and places in Celtic, Scandinavian, and other areas
Edited sentence: This has lead to much speculation on more spurious theories such as that the tribe of Dan were the Danes, or the Tuatha Dé Danann of Ireland, based on the principle that the word Don and Dan appears in many names of rivers and places in Celtic, Scandinavian, and other areas