Animals have certain advantages that humans lack—the ability to sense the Earth's magnetic field is among them. But a new study from California Institute of Technology (Caltech) offer a surprising challenge to widely accepted wisdom. Under the right conditions, the paper says, a select few humans can detect the Earth's magnetic field.
In an experiment biophysicist Joe Kirschvink and his team hooked up 34 participants to an electroencephalography (EEG) machine while recording brain activity monitored from electrodes attached to their scalps. But the set-up, which already calls to mind classic science fiction, gets more unusual.
Kirschvink had his volunteers sit inside an aluminum box without light, known as a . The purpose of a Faraday cage is to block out all electronic signals, including radio waves.
In this unique design (a similar study was done in 2002, Krischvink says there was not enough power), researchers created a magnetic field that imitated part of Earth's, especially around the northern hemisphere. There, the magnetic field slopes downward in steep, dramatic fashion. With a field established, scientists began to rotate, as would happen if a person would turn their head.
In four of the 34 participants, when the field rotated counterclockwise, something happened.
In the four, rotating the field effected their brain's alpha frequency, known as an . The change, which was a drop in waves, was indicative of a brain that is awake but resting.
As with other animals, the cause of the shifting brainwaves was ultimately mysterious. ary MacLean, a neuroscientist at the University of California (UC), Santa Barbara not involved in the work, Science that “I’m convinced that something in the brain is responding to a magnetic field in a particular way. I just have no idea … what mechanism that really represents.”
“Magnetoreception is a normal sensory system in animals, just like vision, hearing, touch, taste, smell, gravity, temperature, and many others,” Kirschvink Gizmodo. “All of these systems have specific cells that detect the photon, sound wave, or whatever, and send signals from them to the brain, as does a microphone or video camera connected to a computer. But without the software in the computer, the microphone or video camera will not work. We are saying that human neurophysiology evolved with a magnetometer—most likely based on magnetite—and the brain has extensive software to process the signals.”
is one of the few common factors that tie together. A rock mineral that also occurs biologically, it appears within the beaks of birds and the snouts of fish. It also occurs within the human brain.
It's too early to say what the detection could mean—possibly nothing, a simple harmless anomaly in the brains of a few. The chances that these four will be able to develop their magnetic brains into their own superpower is very small. But if nothing else, the study shows that the line between animal and human is often smaller than first thought.