Everyone knows birds navigate using magnetoreception, finding their way over huge distances by aligning themselves with Earth’s magnetic field as they undertake their epic annual migrations. However, some scientists believe that the ability to detect the planet’s magnetism may in fact be present in all animals – including humans.

Among the biggest proponents of this idea is geophysicist Joe Kirschvink of the California Institute of Technology, who, at a conference in London in April, presented the results of a small study that he believes proves that people do indeed possess the ability to detect magnetic fields. In an email to Science shortly after giving his presentation, he triumphantly claimed that his research had “nailed it,” providing clear evidence that “humans have functioning magnetoreceptors.”

Magnetoreception has been observed in a wide range of organisms, including some very basic bacteria, which align themselves with the poles of magnets when placed nearby. This has led Kirschvink to suspect that the majority of modern mammals have probably retained this ability from their earliest ancestors.Dogs, for instance, are thought to align themselves along the planet’s north-south axis when pooping. However, since humans don’t regularly use magnetoreception, we’ve sort of forgotten how to do it.

The biggest problem facing Kirschvink and others working in this field is that no one knows how magnetoreception works, as researchers have failed to find any biological components that could function as magnetoreptors, even in animals that are unequivocally known to possess this “sixth sense.” Therefore, while Kirschvink remains convinced that humans do indeed retain this ability, he has no idea what organ might be responsible for it, saying “the receptors could be in your left toe.”

Yet that hasn’t deterred him from investigating. In his latest experiments, researchers passed rotating magnetic fields through participants while measuring their brainwaves. In doing so, they found that when the magnetic field was rotated anti-clockwise, certain neurons responded to this change, generating a spike in electrical activity.

Since the only changing variable was the direction of the magnetic field, the researchers are confident that this activity could only have been in response to this, and therefore conclude that humans are indeed capable of magnetoreception. However, while Kirschvink insists that this experiment proves the presence of magnetoreceptors in humans, it does not reveal where in the body these receptors are located or how they work.