Some Humans Can Detect Earth's Magnetic Field, After All
Human brainwaves in magnetic fields
Long ago, scientists believed animal magnetoreception wasn't possible, and as they began to learn how birds and other animals used magnetoreception to navigate the world, this skepticism moved inward to exclude humans.
After all, the idea of humans sensing magnetic fields sounds like fantasy.
But this assumption has since lost ground to an experiment in 2019 — previously reported by Gizmodo — wherein researchers built a specially equipped Faraday cage. In it, the scientists arranged coils that — when active — generate a magnetic field. The scientists could switch to coils into a "sham mode;" without a magnetic field. But it still seemed to work.
Inside the cage, skeptical test subjects relaxed in a dim, silent space. "During experiments, participants sat with their eyes closed in total darkness. Participants were blind to active versus sham modes, trial sequences, and trial onset timings. The experimental chamber was dark, quiet and isolated from the control room during runs," said the researchers, according to Popular Mechanics.
Magnetic fields make brainwaves
Within the dark, quiet room, all test subjects faced the same way to eliminate directional bias from the magnetic field. Then they were immersed in magnetic forces while researchers recorded subjects' brain waves.
"Our results indicate that human brains are indeed collecting and selectively processing directional input from magnetic field receptors," concluded the scientists. "Such neural activity is a necessary prerequisite for any subsequent behavioral expression of magnetoreception, and it represents a starting point for testing whether such an expression exists."
The researchers' full results expand on how scientists have known that animals experience magnetoreceptivity as a direct biological signal — it's how birds navigate during seasonal migration, and how sea turtles assess the dangers of waterways. And they do this despite subliminal cues from local magnetic fields generated by the environment itself, superimposed on the planet's general magnetosphere.
Volcanoes often generate local magnetic fields, and "an animal moving through magnetic features of this sort will receive a series of warning signals against using the magnetic field for long-range navigation."
Porting magnetic sensitivity to humans
Researchers found the same differentiating capability in humans. "the selectivity of the response favored ecologically valid stimuli, distinguishing between rotations of otherwise equal speeds and magnitudes. This indicates that the effect is due to a biologically tuned mechanism rather than some generic physical influence," they said, reports Popular Mechanics.
This means humans in the study showed brainwave activity that reacted only to mimicry of the global magnetic field of the Earth, without sensitivity to local magnetism flukes. For the researchers, this means humans may have developed their own magnetoreception in the same way animals did: via continued use and long-term incentive.
If we can detect magnetic fields, it's an ability we've actively used, and not because of environmental coincidence. Whether we inherited magnetoreceptive abilities from bygone days of the hunter-gatherer is still unknown, but researchers have high hopes about experiments to come: "The full extent of this inheritance remains to be discovered."