It sounds like a power to be boasted of by the X-Men, but researchers say humans might have the ability to pick up on Earth’s magnetic field.
Many animals, from pigeons to turtles, use it to navigate, while research has shown cattle prefer to align themselves with the field when standing in, well, a field. Even dogs make use of it – albeit when defecating.
But while debates continue about the mechanisms behind such phenomena, it has remained unclear whether humans also have the power of magnetoreception. Now scientists say there are signs that we do.
“We have not as a species lost the magnetic sensory system that our ancestors [millions of years ago] had,” said Prof Joseph Kirschvink, leader of the research from the California Institute of Technology. “We are part of Earth’s magnetic biosphere.”
Writing in the journal eNeuro, Kirschvink and colleagues in the US and Japan describe how they made their discovery after building a six-sided cage, the walls of which were made of aluminium to shield the setup from electromagnetic interference. These walls also contained coils through which currents were passed to produce magnetic fields of about the same strength as Earth’s.
Each participant was asked to enter the cage and sit still on a wooden chair in the dark, facing straight ahead towards the north. During the experiment, the team measured the participant’s brain waves using an electroencephalogram (EEG).
In some experiments the applied magnetic fields were fixed in one direction, while in others they were rotated. In still others the machines were turned on but no magnetic field was produced – meaning the participant was only exposed to Earth’s natural magnetic field. The participant was unaware which experiment was under way.
The results, gathered from 34 adult participants, revealed that certain scenarios triggered a drop in participants’ alpha brain waves – a change that is linked to the brain processing information. This occurred if the applied magnetic field was pointed north and then swept upwards or downwards, or directed down while pointing north and rotated anticlockwise. That is similar to a human in the northern hemisphere nodding their head, or turning their head to the right respectively.
Kirschvink said the responses are akin to the brain “freaking out” – in other words clocking an unexpected change in the environment. Crucially, he said, it means that humans must be able to detect such changes – although the strength of the response varied hugely among participants.
The team say the experiments offer clues as to what the human magnetoreception system might look like – noting that the results rule out electrical induction, or simply artefacts, as explanations.
One possible system that has has been mooted for other animals, particularly birds, is a “quantum compass” based on molecules with unpaired electrons that respond to Earth’s magnetic field. This would allow an animal to tell whether they are moving towards a pole or the equator, but not whether they are headed north or south.
But authors say the new research suggests the human system can tell north from south, supporting an alternative mechanism involving special cells containing iron-based crystals. These crystals are thought to rotate rather like the needle of a compass, opening or closing pores in the cells, thereby affecting signals being sent to the brain.
“We are specifically predicting [these cells’] existence – they have to be there,” said Kirschvink. As all of the participants came from the northern hemisphere, the idea goes that their cells might have become tuned to its magnetic field – hence the ability to tell the poles apart.
The team say modern environments would likely interfere with this “sense”, while there is no sign as yet that such a system is linked to human consciousness, or that it influences our behaviour – although the team say it remains a possibility, and are planning experiments to find out.
Prof Peter Hore, an expert on magnetoreception from the University of Oxford, welcomed the study but said the experiments need to be repeated, including on people from the southern hemisphere, to confirm the findings.
Prof Kenneth Lohmann, an expert in magnetoreception from the University of North Carolina at Chapel Hill, said the study was fascinating and provocative. “Given that a number of other animals can sense Earth’s magnetic field, it is certainly within the realm of possibility that humans can as well,” he said.
However he also urged caution. “It is one thing to find a subtle change in brain activity in response to a weak magnetic field, and another thing to show that people really detect and use magnetic field information in a meaningful way.”
