鳩の帰巣性に関する重要な科学の発展。

New scientific developments shed a new light on the long-standing mystery of a bird’s navigational ability.

I believe an important step has been taken last year towards gaining a truer understanding of the navigational ability of birds. Birds appear to have some sort of highly sensitive “compass” in their eyes’ retina, which is based on quantum phenomena.

Fanciers have long been sceptical about scientists trying to find an explanation for the way in which pigeons navigate. Do they follow a scent trail? This would mean that if a pigeon is released somewhere for the first time, it can already smell its home and that after only a few rounds, either in a group or individually, it would suddenly head for the right direction, even if they are a hundred or a thousand kilometres away from home? Could it be possible that they use highways to position themselves? But what if they have never been in a certain area? Experience has shown that none of these theories can explain the often very quick navigation of a pigeon in an unknown region.

Scientists have now demonstrated that a bird can maintain quantum entanglement of electrons between molecules in its retina much longer than in laboratory systems (Ritz et al.). Because of the longer duration of this quantum state and a change in direction relative to the earth’s magnetic field, birds can actually sense or see in what direction they are flying relative to the magnetic field.

What is quantum entanglement?

Einstein once called quantum entanglement of electrons “spooky action at a distance”, because information between two electrons that were once a pair, can be exchanged instantaneously, no matter how far apart the two electrons are. Instantaneously means faster than the speed of light – which, according to the theory of relativity, should not be possible, but experiments have shown otherwise – and irrespective of time and space. Quantum physicists call this phenomenon non-locality. This entanglement allows birds to sense even the slightest change in an electromagnetic field non-locally, through small chemical changes in their retina. It is remarkable that a field of 15 NanoTesla, which is less than one thousandth of the earth-magnetic field, seemed enough to influence their sense of orientation. This took as long as the quantum entanglement lasted. Apparently, the interaction between the molecules within a bird’s eye seems to give the bird a sense of direction. It had already been demonstrated that a bird’s beak contains magnetite that would be sensible to the earth’s magnetic field, although this was recently denied in an article in Nature magazine, and that pigeons can see polarised light (they can for instance see the sun through the clouds). Still, having a compass does not necessarily mean that you can  find your way home. A human person for example, needs both a compass and a map to find his way in unknown territory. At the moment, no scientist is able to explain how birds or other animals could gather the information that we get from a map. Learning processes as such have been demonstrated among certain species, but this cannot explain relevant orientational situations. The recent findings have also shown some sort of compass functions in birds, but as this study concerns quantum entanglement, it could also reveal something about how pigeons gather the information that we get from maps.

I believe that these new findings in the field of quantum phenomena are a step in the right direction. German researchers have already demonstrated the possibility of quantum coherence in biological systems, in for instance DNA (Gohler et al.). This might sound like science fiction but, take it from me, these are breakthroughs: when biologists enter the field of quantum physics, the strangest things could happen. And that is exactly what people say about a pigeon’s sense of orientation: “This is so strange, how do they do it?” We do not know, but these findings are promising.

Magnetic Compass of Birds Is Based on a Molecule with Optimal Directional Sensitivity
Thorsten Ritz, Roswitha Wiltschko, P.J. Hore, Christopher T. Rodgers, Katrin Stapput, Peter Thalau, Christiane R. Timmel  and Wolfgang Wiltschko
Department of Physics and Astronomy, University of California, Irvine, California
Fachbereich Biowissenschaften der J.W.Goethe-Universität, Frankfurt am Main, Germany
Department of Chemistry, University of Oxford, Oxford, United Kingdom

Spin Selectivity in Electron Transmission Through Self-Assembled Monolayers of Double-Stranded DNA. Science, 2011; 331 (6019): 894 DOI: 10.1126/science.1199339
B. Gohler, V. Hamelbeck, T. Z. Markus, M. Kettner, G. F. Hanne, Z. Vager, R. Naaman, H. Zacharias.