Photo by Erich Ferdinand. Creative Commons Attribution 2.0 Generic license.

Like a disowned half-brother the Neanderthals keep hammering on our door, forcing us to face inconvenient truths.

In the nineteenth century, fossil remains of powerful, thickset, short-necked human-like creatures with massive skulls and protruding brow ridges were found in Europe and recognized as belonging to an extinct species very closely related to us.

It turns out these "Neanderthals" (named after the German valley where the first examples were excavated) left the human homeland in Africa about 300,000 years ago. They migrated north into Europe and had sole possession of our continent for 250,000 years until people like you and I first arrived here, also from Africa, less than 50,000 years ago.

The two species lived side by side, without conflict, for the next 20,000 years — an amazing achievement — until suddenly, around 30,000 years ago, Neanderthals in eastern Europe began to die out. Whatever was killing them spread like a deadly curse. Soon none were left across the whole of Europe east of the Pyrenees. West of the Pyrenees, small populations clung on in isolated refuges in Spain but by 24,000 years ago these last Neanderthals, too, were extinct.

What caused the extinction? It's a great unsolved problem of science. But ever since we started finding the fossils we've been desperate to convince ourselves of one thing. It must have happened because of something inferior, something subhuman, about the Neanderthals themselves. Libraries full of scholarly books tell us they were slow-witted, with brains too simple to handle symbolism or intellectual gymnastics. We're told they had no art, couldn't speak, made inferior stone tools, possessed none of the finer feelings for which we humans pride ourselves and didn't even bury their dead.

So effective has this propaganda been that the word Neanderthal is synonymous for many with bestial, knuckle-dragging stupidity and has been elevated to a noun in wide general use meaning "an unenlightened and ignorant person."

But the picture is changing. We now know that Neanderthal brains were bigger and potentially more sophisticated than our own. There is new evidence that they used body paint, makeup and beads — sure signs of symbolic thinking — and that they did bury their dead, sometimes with flowers. The discovery in Slovenia of a Neanderthal flute carved 43,000 years ago from the femur of a cave bear means they had music after all. The notion that they couldn't speak has proved to be based on a misunderstanding of Neanderthal anatomy. And DNA studies have shown that the FOXP2 gene, linked to language in humans, was also present in Neanderthals.

But one old prejudice long remained unchallenged — the dogma that humans and Neanderthals never interbred. Now the latest DNA evidence, widely reported during 2010, has demonstrated that interbreeding did take place — and on a significant scale. As much as four per cent of our genes are thought to have come from Stone Age liaisons between Neanderthals and humans.

Why should we be surprised? Despite their robust, powerful physiques and their mastery of Ice Age Europe, the Neanderthals did not attack our ancestors when they first arrived as vulnerable new immigrants 50,000 years ago. On the contrary the two groups managed to live side by side in peace — and now we know in love — for 20,000 years.

I've placed the mystery of what happened next at the heart of Entangled, my first work of fiction. It's a fantasy-adventure, timeslip novel set part in the twenty-first century, part in the Stone Age. Brindle is a young Neanderthal man and Ria a young human woman living in northern Spain twenty-four thousand years ago at the time of the final extinction. They're caught up in a cosmic battle of good against evil, and supernatural forces bring them together with Leoni, a troubled teen in modern Los Angeles, to confront a demon who travels through time and seeks to destroy mankind.

I felt the essential humanity of the Neanderthals reaching out to me as I wrote, urging me to explore the possibility that they were highly evolved spiritual beings, pure innocence and love — perhaps less competent with material things than we are, but far ahead of us in matters of spirit. In my story their goodness is raw cosmic power that they use only for healing, to communicate telepathically with one another and to live in balance with the Earth. Beauty and truth shine forth from them but it is precisely these qualities that attract the demon's attention and make him seek their destruction. If he succeeds, the psychic charge he draws from their mass murder will allow him to manifest physically in the twenty-first century and weave the doom of all mankind.

We still don't know how or why the Neanderthals became extinct — although genocide at the hands of our ancestors remains the most likely explanation. We do know that when they were gone from the earth the long era of peace and harmony ended and the age of turmoil and tribulation in which we still live today began.

Perhaps the big question for the future is this. Are we about to weave our own doom and plunge our beautiful Earth forever into darkness? Or is there still time, now that we know the truth about our genes, to find the Neanderthal within ourselves and reconnect with spirit?