In the early days of Egyptology, the compilation of regnal periods was also hampered by a profound biblical bias on the part of Egyptologists. This was most pervasive before the mid 19th century, when Manetho's figures were recognized as conflicting with biblical chronology, based on Old Testament references to Egypt (see Pharaohs in the Bible). In the 20th century, such biblical bias has mostly been confined to alternative chronologies outside the scholarly mainstream.