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Fruit flies do it. The tiny northern wheat do it. Even salmon in the sea does it. All sail using the Earth's magnetic field.
In fact, hundreds of animals migrate this way, some over long distances. But one species has always been excluded from this club of electromagnetic orientation: Homo sapiens. Men and women show no evidence of internal compass possession, the researchers insisted.
But now this view is disputed. In a newspaper in the newspaper in EuroScientists at the California Institute of Technology report evidence that the brains of men and women are responding to changes in magnetic fields and that these alternations could allow them to differentiate from north to south and navigate without a compass.
"We have found evidence that humans have a definitive sixth sense – magnetism," said Professor Joseph Kirschvink, project leader. "This sensory modality is real. This could explain why some people have a better sense of direction than others, for example. It may even be possible one day to restore our ancestral ability to use magnetic fields to navigate. "
The claims, however, are controversial. Other researchers believe that Kirschvink's experiments may have shown that the brain reacts to changes in magnetic fields, but that does not mean that they represent the actions of an internal magnetic sense. "If I put my head in a microwave and lit it, I would see effects on my brainwaves," said biophysicist Thorsten Ritz of the University of California at Irvine, to the newspaper. Science. "It does not mean that I have a microwave sense."
This is a controversial issue and on April 12, it will be the subject of a debate at a conference on animal migration organized by the Royal Institute of Navigation in Egham , near London. Kirschvink will be present. "I'm waiting for sparks to fly," he said. Observer.
In his experiments, Kirschvink – working with colleagues in the United States and Japan – placed volunteers in six-sided aluminum cages that could protect them from the earth's magnetic field. The brainwaves 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 some of the orientations they induced in magnetic fields resulted in a significant fall in alpha brain waves. Such changes normally occur when the brain processes information. "Essentially, their brains were panicking 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 claims that humans can detect and exploit magnetic fields," said Professor Peter Hore of Oxford University.
In addition, the results obtained by Kirschvink volunteers are modest compared to the types of magnetic field responses obtained by other species, such as the Northern Wheat Bird, which regularly travels from Alaska to Kenya for short trips. returns over 30,000 km.
"We have studied northern wheat in the lab and we know that they react to changes in magnetic fields, so it's hard not to believe they're doing the same thing in nature," Hore added. who will also attend this week's meeting. "Of course, when they approach their destination, they probably use other meanings and clues: their sense of smell, the sun and the stars, for example. Nevertheless, it is clear that northern wheat has remarkable power in detecting magnetic fields. "
With respect to the mechanism used by Whearsear to navigate, Dr. Hore believed that the birds used photosensitive molecules that could be transformed into one of two different chemical states depending on the direction of a field. magnetic like that of the Earth. "These chemicals, called cryptochromes, are found in the retina of the bird's eyes and act like an internal compass," said Hore.
Kirschvink takes a different point of view. He claims that his research suggests another explanation: the existence of special cells containing iron-based crystals. These turn a bit like the needle of a compass, opening or closing pores in the cells and modifying the signals sent to the brain. "They must be here," he says.
To explain why we do not see people using the internal compass to navigate, modern life may have wiped out their relatively weak operation in humans, argues one.
For example, Kirschvink cites studies of Asians and Australians who speak the fundamentally different languages of European languages. These differences could affect our ability to respond to weak signals from our "internal compasses".
"These people do not have words for the front, the back or the right. Instead, they talk about looking in a direction to the north or turning to the east. They are geographical reference languages and they are still spoken by the natives. "
Kirschvink added that such languages would be better suited to respond to internal compasses and would help men and women think in ways that keep them in touch with their innate abilities to navigate. "European languages, which have an egocentric repository, could now block our ability to use our brain in this way," he added.
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