The sixth sense: can humans detect the magnetic field of the Earth? | Science

Fruit flies do it. The tiny trout of the north do it. Even salmon in the seas do it. All navigate using the Earth's magnetic field.

In fact, hundreds of animals migrate in this way, some over long distances. But a species has always been excluded from this electromagnetic orientation club: Homo sapiens. Researchers have insisted that men and women show no evidence of internal compbades.

But now this point of view is being challenged. On a paper in the magazine. eNeuro, scientists at the California Institute of Technology report evidence that the brains of men and women respond to changes in magnetic fields and these alternations could allow them to differentiate from north to south and navigate without compbades.

"We have found evidence that humans have a definitive sixth sense: magnetism," said project leader Professor Joseph Kirschvink. "This sensory modality is real. It could explain why some people have better directions of direction than others, for example. It might even be possible someday to restore our ancestral capacity to use magnetic fields to navigate. "

The claims are controversial, however. Other researchers say that Kirschvink's experiments may have shown that the brain responds to changes in magnetic fields, but that does not mean that they represent the actions of an internal magnetic sense. "If I had to put my head in a microwave and turn it on, I would see the effects on my brain waves," said a biophysicist, Thorsten Ritz of the University of California, Irvine. Science. "That does not mean it has a microwave sense."

It is a controversial issue, and on April 12 it will be discussed at a conference on animal migration held by the Royal Institute of Navigation in Egham, near London. Kirschvink will attend. "I hope the sparks fly," he told the Observer.

In his experiments, Kirschvink, working with colleagues in the USA. UU And Japan, placed volunteers inside six-sided aluminum cages that could protect them from Earth's magnetic field. The brain waves of the participants were measured while different magnetic fields were artificially induced inside the cages.

A total of 34 men and women participated, and the team discovered that certain orientations they induced in the magnetic fields caused their alpha brain waves to decrease significantly. Such changes usually occur when the brain is processing information. "Essentially, their brains were going crazy in response to changes in magnetic fields," Kirschvink said.

Other scientists are more cautious. "This is a very interesting research, but it needs to be replicated before we can think of backing up claims that humans can detect and exploit magnetic fields," said Professor Peter Hore of the University of Oxford.

In addition, the results produced by Kirschvink volunteers are modest compared to the types of responses to magnetic fields achieved by other species, such as the northern wheat bird, which regularly travels from Alaska to Kenya on return trips of approximately 19,000. miles

"We have studied northern wheat in the laboratory and we know that they respond to changes in magnetic fields, so it is hard not to believe that they are doing the same in nature," said Hore, who will also attend the meeting. week. "Of course, when they approach their destinations they probably use other senses and clues: their sense of smell, and the sun and the stars, for example. However, it is clear that northern wheat has a remarkable power when it comes to detecting magnetic fields. "

Regarding the mechanism exploited by the wheat to navigate, Hore said he believed that birds used photosensitive molecules that can be converted into one of two different chemical states according to the direction of a magnetic field like Earth's. "These chemicals, called cryptochromes, are in the retinas of birds' eyes and act as internal compbades," Hore said.

Kirschvink has a different vision. He says his research points to an alternative explanation: the existence of special cells that contain iron-based crystals. These rotate like the needle of a compbad, opening or closing pores in the cells and altering the signals sent to the brain. "They have to be there," he says.

As for why we do not see people using internal compbades to navigate today, modern life may have destroyed their relatively weak operation in humans, it is argued.

For example, Kirschvink points to studies on Asian and Australian people who speak languages ​​that are fundamentally different from European languages. These differences could influence our abilities to respond to weak signals from our "internal compbades".

"These people do not have words for the front or back or to their right, instead they talk about looking north or turning east, these are languages ​​of geographic reference and are still spoken by the aborigines."

Such languages ​​would be better suited to respond to internal compbades, Kirschvink added, and would help men and women think in a way that keeps them tuned to their innate navigational skills. "European languages, which have an egocentric frame of reference, may now be blocking our ability to use our brains in this way," he added.

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