Planet Earth possesses several remarkable traits. Not only is it home to the only confirmed life in the universe, but Earth is also a giant magnet, and although they are likely unaware of it, many of the organisms which reside here rely on our planet’s magnetic properties to orient themselves with their environment.
While several different species are known to rely on this unique capability during migration and other functions, how it works remains mysterious, and some studies may even indicate that humans could exhibit such abilities.
Much of our understanding of magnetoreception stems from the seminal work of Cornell University professor William Keeton, whose many students that flocked into his lectures referred to his biology class simply as “The Keeton course.” However, it was his 1970 paper, "Magnets Interfere with Pigeon Homing", which became a landmark in studying how animals orient themselves according to the planet’s magnetic field.
Keeton found that when homing pigeons became acclimated to lab conditions in a different time zone from that which they normally reside, they had difficulty orienting themselves correctly in clear, sunny weather, while on overcast days they seemed to have less trouble. Keeton devised the theory that these birds would rely on magnetic fields for their orientation and travel under certain conditions. This led to experiments where magnets were attached to the backs of some of the birds, which seemed to help confirm that magnetic interference disrupted their natural ability to orient themselves using the planet’s magnetic field as a guide.
There are a few ways that have been proposed that may explain how magnetoreception is believed to work, although the two main hypotheses involve a sort of “chemical compass” that relies on what is called a radical pair (a very quick reaction where a pair of radicals are formed in tandem with antiparallel electron spins), and the other proposing that magnetite particles could explain the phenomenon.
A so-called “magnetic molecule” was proposed in 2000 which might naturally house radical pairs. Known as cryptochrome, this molecule is a flavoprotein that can be found in the eyes of many animal species and remains the only known protein capable of producing radical pairs in animals through the process of photoinduction, particularly during exposure to blue light. With the weakness of the Earth’s magnetic field, the radical pair mechanism is largely viewed as the only way that chemical changes could actually be affected by it.
Birds aren’t the only animals that appear to possess such capabilities. In addition to birds, a range of marine animals from porpoises, to sharks and sea turtles appear to rely on the Earth’s magnetic field to orient themselves. Even some snails appear to possess the use of a natural magnetic “compass.”
With its prevalence in nature, it seems reasonable to ask whether humans might also possess the ability to navigate with help from the Earth’s magnetic field.
Beginning in the 1970s, English scientist Robin R. Baker began to conduct experiments involving the degree to which humans appeared to display magneto-receptive capabilities. In Baker’s experiments, several test subjects were blindfolded and then asked to attempt to “sense” the location of their homes, as well as to find north. Even despite traveling long distances from their place of residence, some of Baker's subjects still seemed to be able to accurately determine what direction they came from. Also intriguing was that while blindfolded, many subjects appeared to perform better than they did when they were able to rely on sight to help orient themselves.
Perhaps even more intriguing than the visual element had been that when magnets were attached to these subjects as Keeton had done with his homing pigeons, they appeared to experience interference with their magnetic sense. As a control, brass weights were used with some subjects who, despite believing magnets were attached, appeared to experience little or no interference with their ability to sense directions correctly, and also detect which direction their homes were.
Additional research throughout the decades has shown that cryptochrome, the so-called “magnetic molecule” found in many animals, is also present in the human eye. If this molecule and its chemical properties do indeed lay at the heart of the mystery of magnetic reception in animals, should it necessarily seem so unlikely that at least some humans could possess this trait as well?