Most people accept that homing pigeons have a sixth sense when it comes to navigation, but did we at some point, also have the same ability?
Scientists who investigate the world of magnetoreception are often labelled as mavericks. Why is it more appropriate in natural sciences, to study migratory birds, than devote your career to the discovery of our own expanded sensory range? It is now accepted as fact, that honey bees, frogs, toads, newts, fish and many other taxonomic groups all possess an internal compass that responds to the earth’s faint magnetic field lines. In recent years, researchers have discovered deer and cattle aligning themselves when grazing, and even more bizarrely, dogs facing North or South to urinate.
Up until now, most studies of magnetoreception have been based on behavioural changes in relation to an applied magnetic field, without discovering the underlying biological mechanism in control. Some scientists however, such as David Dickman, a neurobiologist at the Baylor College of Medicine in Houston, Texas, did manage to pinpoint activity in the neurons from the inner ears of pigeons when exposed to magnetic fields. With no definitive magnetic sense organ, discovering the seat of detection and corresponding reaction to magnetism could take many more years of research.
There are currently two rival theories regarding magnetoreception, both of which are proposals put forward by geophysicist, Joe Kirschvink, from Caltech in Pasadena, California. The first of his ideas, is that magnetic fields trigger quantum reactions in proteins called Cryptochromes. These proteins are found in retinal tissues, and oddly, also in the pineal gland seated inside the brain. Unfortunately, no one has determined how those proteins might control neural pathways.
Kirschvink favours his second theory, that suggests the presence of miniature needles within receptor cells of nerves sited behind the nose of an animal or inside the inner ear. He assumes that these needles are composed of magnetite, which then has an impact on the functioning of nerves. Why or how that is achieved remains a puzzle, but magnetite has been discovered in the sinus tissue of yellowfin tuna, the stomachs of honey bees and in the surface materials of some molluscan feeding plates. Some mud dwelling bacteria also use magnetite as a sensor, actively heading North in the northern hemisphere and south in antipodean locations.
Since humans also possess Cryptochromes, Michael Winklhofer, a biophysicist at Oldenburg University in Germany, suggests that we too, could retain the ability to sense magnetic field lines. Early studies of blind-folded student volunteers pointing to the direction of home, following a wandering journey, are universally discredited. Scientists are now directing their attention to less behavioural evidence, in favour of more neurological studies. With a generous grant, the Human Frontier Science Program, employing scientists such as Kirschvink, Shimojo and Matani, is attempting to analyse the neural activity of humans via EEG readings. Their study subjects volunteers to controlled magnetic fields within a shielded Faraday cage. This protocol may not reveal the presence of a magnetic receptor itself, but it will show the direct effects on human brainwaves.
Early indications show that when a magnetic field is rotated clockwise, there is a sharp drop in alpha waves in the subject. This is the equivalent of the volunteer looking to the right, and is associated with brain processing. With all other senses deprived of stimuli, the only conclusion that can be drawn is that the brain reacts to a magnetic field. A similar signal was also detected when the field was directed towards the floor. In brain terms, it was as if the subject looked upwards.
These are easily replicated findings, and the start of some very exciting studies. In my humble opinion, I feel that the same experimental rigor should be applied in relation to testing the Cryptochrome theory, since a new and controversial claim, put forward by Can Xie, a
biophysicist from Peking University, that complex magnetic iron structures, surrounded by cryptochrome proteins, have been discovered in the retinal tissue of fruit flies. Xie asserts that these complexes are the long sought after magnetoreceptors.
What if we too have these complexes, but science has yet to find them? After all, humans were navigating the planet long before the invention of sextants and compasses. As wonderful as the notion of a sixth magneto-sense is, I don’t think I will be relying on instincts to find my way home after a long journey. Thank the heavens for SAT-NAV. It is one of my favourite inventions.
Sam Nash is the author of the sci-fi conspiracy thriller, The Aurora Mandate. Release date TBA. You can find her at https://www.samnash.org or on Twitter @samnashauthor or Facebook.com/samnash.author.