A protein in the retina of the human eye can perceive magnetic fields.
This was discovered by researchers at the Medical School of the University of Massachusetts, led by neuroscience and neurobiology professor Steven Reppert, who published their study in the journal Nature communications.
First of all, let’s talk about the Earth’s magnetic field.
How the magnetic field of Earth is created
What creates the magnetic field? Differences in temperature, pressure and composition within the outer core cause convection currents in the molten iron, because cool, dense matter sinks, while warm, less dense matter rises. This flow of liquid iron generates electric currents, which in turn produce magnetic fields.
Nowadays, there is an amount of data collected by satellites, which depict the contemporary magnetic field. This data reports something quite surprising. There is a part of the Earth, deep at the core-mantle boundary, somewhere beneath southern Africa, where polarity is reversed. In this region deep down the Earth, a compass, if we could actually place one down there, would point to the south.
This region is the basic reason that leads to the South Atlantic Anomaly. And simulation experiments have shown that such regions are observed right before magnetic reversals. Furthermore, it is known that such reversals have taken place before, and the last one known was 780.000 years ago. So scientists are trying to find out information about the past and in specific, before those 160 years.
Looking into the past with Archaeomagnetism
Archaeomagnetism constitutes a cooperation of archaeologists and geophysicists in order to find out information on the magnetic field of the past. Clay pottery can be used for instance, as clay contains magnetic minerals and when it is heated to make a utensil and cooled again, it records information on the magnetic field of the time. So, if the exact age and origin of the clay pot can be identified with the radiocarbon dating method, we have evidence concerning the magnetic field of the time.
Until now, there had been information only about the Northern Hemisphere and no data on the Southern, which is the region scientists need to analyze, to find out about the creation of the South Atlantic Anomaly. But luckily, Iron Age people that lived in South Africa between 2.000 and 1.500 years ago, used clay to build their huts and to mold grain bins. And as rainfall was quite important to them, they had certain rituals against drought, including burning their granaries. So the same way as heated and cooled pottery, the clay of these huts and bins offers scientists important information on the magnetic field of that period.
The new research on the magnetic sense of humans
The unexpected discovery opens once again a neglected chapter of the biology of consciousness that has to do with the so-called magnetic sense. In all the animals of our planet, the photosensitive chemical reactions involve an ancient protein, the flavoprotein (cryptochrome), which plays an important role in understanding the Earth’s magnetic field. Experiments on Drosophila flies have shown that these proteins function as light-dependent magnetic sensors.
The new research showed that the human cryptochrome protein hCRY2 provides a similar magnetic sensory ability. The researchers created a mutant fly, which, thanks to an added human gene, produced the corresponding human cryptochrome protein instead of producing its own flavoprotein. As it turned out, the fly still could perceive magnetic fields.
The experiment revealed that the human protein hCRY2has an inherent molecular ability to function as a magnetic sensory system, which can pave the way for further research of the unknown magnetic senses in human.
However, scientists have not managed yet to agree whether and at which degree people can sense the Earth’s magnetic field. But there are some indications that geomagnetism affects our visual system of light perception. But whether the human eye functions as a magnetic “compass” is still an enigma.