Graham Hancock is one of the most prominent writers of what we might call "Fringe History", which has a similar relation to scholarly history as the Daily Mail's Health Scares have to scientific medicine.
There are a number of themes in fringe history, which writers repeat and copy from one to another. A typical area is "Bermuda Triangle" where numerous writers cite each other's reports of incidents, none of which can be supported by real research. That is the most important feature - lack of scholarly methods.
Some of these fringe writers however have made up stories about things that can be solved with research. Thus, 50 years ago Plate Tectonics was largely unresearched. Hancock cites books by Charles Hapgood, a fairly respectable academic, who wondered whether the continents could have moved swiftly. The thing to note about Hapgood's thinking is that even according to Hancock's bibliography his first book on the subject was published in 1958 and last in 1970 - many years before the details of Plate Tectonics were worked out. People who continue to cite his work are ignoring the way science has moved on since then. Now we know exactly how fast continents move (the Atlantic has widened by the length of two football pitches since 1492), and in addition the mechanism of movement is known (convection currents deep in the crust).
Charles Hapgood - Wikipedia article
So at that time - the 1960s - these writers could postulate that a huge sudden movement of the axis of rotation of the earth had occurred, even during the time humans had been on earth. Modern scientific research, based on the body of observations and theory that make up the scientific process, show that this couldn't happen. Hancock and other writers continue to ignore the modern research and go on repeating the long discredited suppositions of the past - the very opposite of a scholarly attitude.
Another typical theme is based on such documents as the Pir i Rais map, allegedly showing the Antarctic without ice. Real research shows the age of the ice by means of drilling ice cores. There can be no doubt that there has never been a period while humans existed when the continent was free of ice. Which should we trust for information about the ice: actual measurements of ice cores, or a document of disputed provenance? The physical data should take precedence in believability.
Here is some detailed criticism of the Pir i Rais stories. Debunk of Piri Rais map
Another favourite theme is Templars. While it is certain that this organisation flourished during the time of the Crusades and shortly afterwards, the stories of "secret practices" and beliefs they held are entirely imaginary - in the sense that there is no reliable evidence about what their beliefs were, if indeed they differed from the Catholic mainstream. The excuse given for their suppression was that they were heretics, but it is clear this was only a form of words intended to justify the real reason for the French king's desire to abolish them - their riches, which he hoped to obtain as he owed them a great deal of money to pay for his wars. Thus the tales of their unorthodox beliefs show all the signs of being fabrications of the type used by Stalin's prosecutors in the Great Purge of the 1930s.
A study of the economic results of the Templars' activities would be more rewarding, as it can be argued, and has been, that the Templars contributed much to the growth of the economy in Europe simply by acting as a bank and by moving their produce under armed guard. More trade was one of the ways by which feudal anarchy came to an end. Far more interesting than their alleged religious and philosophical activity was their role as a multi-national economic organisation, covering the whole of Europe, answerable only to the Pope, and not paying taxes to the kings.
It is possible of course that their experiences in the Middle East brought them into contact with cultural forms different from those in Europe - something that is often attributed to the effects of the Crusades on European culture. It may even be that the Templars learned to be more tolerant of the other religions in the Middle East, even as far as talking to the Assassins (ancestors of the modern Ismaili community). There is some evidence for this in Usama ibn Munqidh's account of a Templar in the al Aqsa Mosque (see Anthology of Islamic Literature in Crusades). Tolerance in itself might have been seen as a heresy back home where there was an atmosphere of totalitarianism. If so, this was something they shared with the Norman rulers of Sicily who associated with Jews and Muslims. The career of the Holy Roman Emperor Frederick the second, king of Sicily as well as emperor, is a good example. He too was in bad odour with the Pope. He had Muslim ministers in Sicily and perhaps a Harem - and also founded educational institutions. The real cause of intellectual change was education - then as now - something religious fanatics oppose.
But absence of evidence doesn't prevent huge numbers of books being sold about their supposed beliefs, and even more unlikely descendants today. Sometimes the Freemasons are claimed to be descendants of the Templars, on rather dubious grounds. They themselves seem to know almost nothing about their origins, something that fringe writers feel able to describe in detail without the need for backing documents.
Rennes le Chateau and its numerous spinoffs
One spinoff has been the very profitable series of books by Dan Brown who worked it up into a lucrative fiction franchise.
There seems to be a psychological type that likes to deny consensus. For example, there is a group that denies that HIV causes AIDS - or even doesn't exist. This apparently harmless lunacy (often associated with right wing politics) is estimated to have caused the deaths of 350,000 people in South Africa, as their nonsense was taken up by former president Thabo Mbeki, who based his policy on the disastrous idea that AIDS was simply a disease of poverty.
Creationism and religious stories
The main effect of religious interpretations and distortions of history may come in the Middle East where the Palestine problem is complicated by laughable theories of "end times". The real history of the area may well be different from the various religious mythologies.
Book of Mormon
Once again, these beliefs can only be held by ignoring the body of knowledge made by using the scientific method.
Frances Yates - The Rosicrucian Enlightenment
A respectable academic historian looks at what people believed in the 16th century
David Aaronovitch - Voodoo Histories, the role of the Conspiracy theory in shaping modern history.
Charles Fair - The New Nonsense
The New Nonsense: The End of the Rational ConsensusA canter through some of the nonsensical things people believe these days.
Ron Fritze on Fake History
"As an editor at a major publishing company told a friend of mine several years ago, bunk sells, debunking doesn't."
His book Ronald Fritze - False History
Invented Knowledge: False History, Fake Science and Pseudo-religions
What do professional historians know about the Templars
The Templars - Manchester Mediaeval texts
The Templars: Selected Sources (Manchester Medieval Sources)
Malcolm Barber - the New Knighthood - History of the Templars
The New Knighthood: A History of the Order of the Temple (Canto)
Der Templerprozess. Das Ende des Ritterordens
Le Procès des Templiers
Michael Shermer - Why People believe Weird things
Why People Believe Weird Things: Pseudoscience, Superstition, and Other Confusions of Our Time
Marylin Hopkins - Rex Deus - the True story of Rennes le Chatateau
Rex Deus: The True Mystery of Rennes Le Chateau and the Dynasty of Jesus
Rex Deus : Le Véritable secret de la dynastie de Jésus
Michael Shermer - Denying History
Denying History: Who Says the Holocaust Never Happened and Why Do they Say It?