For the First Time, the Source of a Strange Quantum Sense Is Discovered in an Actual Migratory Bird
When you are as small as a European robin, traversing the continent for the winter is no easy task. We now understand how it maintains its course across vast distances – an intrinsic capacity to harness the strangeness at the heart of quantum physics.
Long suspected as a way for animals to detect the tug of the Earth’s weak magnetic field, a non-classical reaction to light has been seen within a protein expressed in the eyes of a night-migratory songbird.
The cryptochrome protein complex of the small bird was put through its paces by a cooperation of researchers from institutions around the world to determine how it responded to being illuminated constantly and in bursts of blue light, both inside and outside of a modest magnetic field.
While the discovery falls short of establishing that the little birds rely on a quantum quirk of chemistry to navigate across Europe, it gives critical support for the notion of magnetoreception’s function in navigation.
Earlier this year, researchers at the University of Tokyo discovered that a similar protein found in humans can respond differently to blue light depending on the strength of a neighboring magnetic field.
Certain atoms in the protein with a single electron swinging about in its outer shell may form what is known as a radical pair, effectively entangling their properties.
A magnetic field can have an effect on the nature of this connection. When a radical pair is exposed to a precise dose of energy in the form of blue light, they glow differently depending on their state of entanglement.
In other words, the quantum nature of the interaction between two electrons in the correct protein structure enables light to communicate the intensity of a magnetic field, even one as feeble as the Earth’s.
This was a very remarkable discovery, one that clearly hinted there was more to biochemistry than conventional physics alone could explain.
Additionally, it held the potential to explain how certain species, such as migrating birds, would be able to’see’ the alignment of field lines separating the planet’s magnetic compass points, a capability that could be useful for navigation.
There was only one issue — the cryptochrome was human, originating from human cells. What this means for our own biology is unknown, but the potential for cryptochrome’s influence on other creatures has remained a point of contention.
The debate has been significantly narrowed, however, by the discovery that a cryptochrome purified from the genome of the European robin (Erithacus rubecula) – an animal that migrates occasionally from frigid Russia to warmer habitats in western and southern Europe – exhibits the same magnetically induced quantum behavior.
The researchers compared the robin’s cryptochrome to a comparable protein complex derived from chickens (Gallus gallus), a species not known for undertaking difficult treks beyond crossing the occasional road.
Additionally, the researchers studied cryptochromes extracted from domestic pigeons (Columba livia). Although pigeons are well-known for their ability to navigate great distances, they are not strictly migratory, which leads the scientists to assume that its own cryptochrome did not evolve under the same stresses as the robin’s.
Laboratory investigations indicate that robins’ cryptochromes are capable of perceiving the modest influence of the Earth’s magnetic field, more so than those of chickens and pigeons.
Future investigations on live people will need to be conducted in a humane and ethical manner if we are to confirm that the quantum operations of cryptochrome are indeed what tell robins which direction to head for a warm winter rest.
As for what the tiny bird’sees’ when it detects a magnetic field, we can only speculate.
Perhaps a stronger reactivity in one direction to blues in the environment? Perhaps it sees nothing – only a vague sense that one method is preferable to the other?
There are some secrets that not even quantum strangeness can uncover.
This study was published in the journal Nature.