GRAHAM HANCOCK is breathless. He's telling me about his first hallucinogenic trip in the Amazon jungle, and he just can't get the words out fast enough. The former journalist and now bestselling science writer spent five weeks living with indigenous Indian shamans in Peru, where he ingested a sacred plant drug known as ayahuasca.
We pick up the story just after the shaman began the ritual ceremony by singing the icaros, ancient chants which draw the spirits around the circle. Hancock then took a sip of the drug, which he describes as a "vile-tasting liquid, so strong and bitter-sweet and salty, so dark and concentrated as to be repellent". His muscles involuntarily relax, he closes his eyes and then the visions begin.
"I had a very scary beginning to that trip," he says. "I saw incredible transformations of different animals and beings glowing with light that appeared directly in front of my field of vision. It was a typical scene which many describe as an alien abduction. They were very anthropic, and definitely wanted to communicate with me. It was rather like going to a strange new country, where I had to start learning the rules of communication."
Getting deeper into the experience, Hancock took another dose of the drug, but his body couldn't take it. The nausea came on strong and soon he was out in the dark, puking. Before long he was drenched in sweat with only dry heaves left. He sank to the ground and called an end to the trip because he was so afraid. He opened his eyes, and the visions left him. You could conclude from this account - detailed in Hancock's latest book, Supernatural - that Hancock is just another traveller keen to acquaint himself with the customs of new cultures. But there is a little more to this trip than meets the eye.
A reporter by trade, Hancock was born in Edinburgh before moving to India in his childhood. He returned to attend school and university in Durham, from where he graduated in 1973 with a degree in sociology. He went on to pursue a career in journalism, writing for The Times, The Sunday Times, The Independent and The Guardian.
But in the 1980s he gave up newspaper reporting to pursue his own passion - the lost civilisation of man. In the past 20 years, he's written several books including the best-selling Sign and Seal on the Ark of the Covenant - as well as filming documentaries about his research.
"Three years ago I decided to go back to the subject which fascinated me at university," he says. "I was interested in human origins, in what makes us different from the apes. I found that it wasn't the use of tools, as many people believe, but abstract thought and the ability to manipulate symbols." The answer was art. Cave paintings and writings which depicted thoughts and visions, none of which have ever been achieved by other species. In fact, even our human ancestors had no artistic capability. Or not until 40,000 years ago, at least.
"Previously, we were very uncreative and boring. We used the same tools continually without modifying them. Then, suddenly, a light switched on in our brain. Fossils from 40,000 years ago show that we began to explore spirituality, looked for signs of life after death and innovated specialised tools. And we began to paint. In France, Italy and South Africa and all over the world, they've discovered incredibly accomplished paintings, but no explanation for this burst of development."
This has been termed the "greatest riddle in archaeology", and many academics have devoted their career to its study. The reason behind the sudden transformation, the majority have concluded, is hallucinogenic plants. Magic mushrooms would be a relevant example, but all over the world, man stumbled across drugs which opened the possibility for spiritual, creative thought.
Professor David Lewis-Williams, of South Africa's Witwatersrand University, believes that is the end of the story. These visions - and therefore the art they produced - were universal because all of mankind has the same neurology. Our brains are wired in the same way, so when we take these drugs, our bodies have the same response. Indeed, at the University of New Mexico, researchers have found that volunteers given hallucinogenic drugs drew the same kinds of paintings as those found in the ancient caves. This, coupled with a wealth of other evidence, supports Lewis-Williams' theory that drugs are the answer.
For most people that explanation would suffice, but not for Hancock. He could not accept that the beginnings of human spirituality came down to brain chemistry. For him, there had to be more to it, and he decided to investigate, hence the first-hand research trip.
What he has found - and what forms the basis of his new hefty tome - is a theory that to many will sound absurd. He believes that when shamans and drug users experience these hallucinations, they are actually tapping into a parallel universe. The visions - be they of fairies, elves or aliens - are real, they exist all the time, and they want to communicate with us.
"Think of it as though the brain is like a TV receiver. In order to cope with everyday life, we have to tune into "Channel Normal" for the majority of the time. But if we retune our brains with these drugs, or alter our state of consciousness through rhythmic dancing and drums, we can see images of the parallel dimensions."
Hancock does not prescribe for a second to the idea that when people experience "alien abductions", they are seeing foreign creatures that may whisk them to another planet. What he does believe is that the spirits dwell in this other dimension, and if we let them, they will continue the teaching that they gave to our ancestors.
"I believe these hallucinogenic experiences are the basis for all modern-day religions. If you think about it, why would we ever have cause to imagine a spirit world? Our uncreative ancestors didn't, but then they found these drugs and saw for themselves the spirit world, and realised there was more to life. I think religion resulted from the need to explain these supernatural encounters."
A sceptic would maintain that, outwith the experience of those on drugs or in a trance, there is no evidence to support Hancock's theory. And many could take offence to his assertion that when Mohammed, Jesus Christ and St Paul thought they were experiencing God, they were, in fact, just accessing the parallel world. Part of the problem with accepting this higher plane comes in locating its origin. If these spirits are the "ancient teachers of mankind", as he says, where did they come from? In this instance, as with every other, Hancock points to science. Prepare for the most astonishing claim yet. "The secret could be in our DNA," he says. "When Francis Crick, the discoverer of DNA, died, it was revealed that his first vision of the helix module occurred while he was on LSD. Although he was an atheist, he then published a book which subscribed to the theory of intelligent design, that our universe was not simply the result of a series of chemical accidents.
"In brief, what he said was that after the Big Bang, life did not evolve first on Earth. At the far side of the universe, another civilisation developed, a highly advanced civilisation who surpassed the stage we have currently reached. He asserted that in some way their world became threatened - global warming, or some such catastrophic event - and so they devised a way to pass on their existence. They genetically-modified their DNA and sent it out from their planet on bacteria, with the hope that it would collide with another planet. It did, and that's why we're here." What Hancock goes onto explain is that the DNA was encoded with messages from that other civilisation.
They programmed the molecules so that when we reached a certain level of intelligence, we would be able to access their information, and they could therefore "teach" us about ourselves, and how to progress.
Of course, this talk of aliens sending off bacteria sounds like the ramblings of a deranged guest on a Jerry Springer show. But the astonishing thing is that Hancock is intelligent and articulate, and his writing is as expert as you would expect from an esteemed international correspondent.
Precisely because he is so credible, his idea will no doubt entice those looking for more conspiracy theories, and you need only look as far as Dan Brown to see the commercial success available.
But to give him credit, Hancock at no point claims these discoveries for himself, he always points to archaeologists and scientists who have been fascinated by similar concepts. Indeed, all that he asks for is that people more qualified than himself, investigate the questions he raises.
"I know [this] sounds preposterous and pointless to anyone committed to objective science. The more closely I pursued these questions, however, the more convinced I became that they point towards matters of extraordinary substance, and that science has done us an immense disfavour by its policy of ridiculing and discouraging all rational inquiry in this area."
Supernatural by Graham Hancock 20 published by Century. Graham Hancock will be appearing at Borders, Glasgow on 18 October at 6pm. Tickets available on 0141 222 7700.