In part 1 of this series, I explained various studies involving magnetoreception in trout, pigeons, sea turtles, and other creatures. Amazingly, the data suggest that some animals possess sensitive magnetoreceptors that read and interpret small variations in Earth’s magnetic field, and also possess inborn, internal navigation maps. But how did these animals obtain such traits?
An article from Current Opinion in Neurobiology speculates about an evolutionary pathway: “The widespread distribution of organisms…that are magnetoreceptive argues that this sensory modality evolved prior to the radiation of the animal phyla.” The authors “suggest that magnetoreception has evolved through the process of ‘exaptation,’” which involves the elaboration of a biological system as an ancillary survival tool.1
Fair enough, but what does this mean in practice? The article seems to be saying that, although most animals are magnetoreceptive, only some creatures discovered that they had this capability and applied it. Animals so endowed would meet the “survival of the fittest” criteria; perhaps it led them to fertile grazing and/or hunting areas more efficiently. The probability of this occurring through small evolutionary steps seems intuitively daunting in the mere 500 million years since the emergence of modern fauna, but let us concede that point for sake of argument and move on.
Magnetoreceptor systems in animals can be extremely complicated. For instance, a 2008 article in the Journal of Comparative Physiology A reported, “light is indeed required for magnetic compass orientation in birds and salamanders.”2 The researchers noted that when young homing pigeons were placed in total darkness, they seemed to be disoriented. Although light is electromagnetic, there is no magnetism associated with a beam of light; so it has no obvious relationship to magnetoreception except perhaps as a trigger. Furthermore, “a wavelength-dependency of magnetic compass orientation was reported for salamanders, passerine birds, and homing pigeons.”3 In other words, only certain frequencies of light trigger magnetoreception!
Presumably, if animal brains can evolve complex “computer” systems to determine location based on the Earth’s magnetic field, there isn’t any reason why these systems couldn’t evolve so that they would turn on and off due to light and/or different wavelengths of light. That these two features would evolve together seems increasingly improbable, but for the sake of argument, let’s concede these evolutionary steps.
The internal navigation map seems the most difficult feature to explain by gradual neo-Darwinian evolution. How could it evolve by trial-and-error? How many pied flycatchers perished crossing the Alps, the Mediterranean Sea, or the central Sahara over how many millennia before a lucky pair emerged with an internal map that allowed them to migrate safely around these obstacles—and passed this trait on to their offspring? How did the species even survive this process? And how many swallows died—unable to fly south for the winter and return north for the summer—until, finally, one fortunate pair evolved an internal magnetic map that returned them to Capistrano every March 19? Building such a map seems an incredibly complex process with an incalculable number of variables and a vanishingly low probability verging on the impossible.
Yet one additional feature must be added to the internal magnetic map: a trigger, perhaps unrelated to magnetism, that tells the animals when to migrate. Migratory birds are well dispersed in the summer, but they migrate together in huge flocks in the fall. Either there is a bird hierarchy that communicates the need to migrate, or the birds have an internal inborn alarm that tells them when to go—and such an alarm adds another trait which increases the difficulty of justifying the gradual evolution explanation.
Moreover, why did such evolution only occur in lower animals? Why didn’t humans evolve a brain function to utilize our internal magnetoreceptors? A PNAS article reports that cattle and deer are affected by the Earth’s magnetic field.4 Wouldn’t this have benefitted early human hunter-gatherers? Those who evolved magnetoreception would surely be among the “fittest,” able to return to the best food-producing areas in season. If magnetoreception is due to natural selection, why did it pass us by?
All this illustrates the problem with the evolutionary model. The first step is spontaneous evolution of a magnetoreception system, but that alone is not sufficient. Migratory animals must also evolve a magnetic “map” to and from the correct destinations, preprogrammed into the brain, apparently from birth. And as a final step, they must also evolve some kind of a seasonal trigger to tell them when to migrate. All this seems totally improbable—impossible even—within any reasonable evolutionary timeframe. To the contrary, well-designed, preprogrammed magnetoreception systems seem much more probable within a creation model.
Dr. Hugh Henry, PhD
Dr. Hugh Henry received his PhD in Physics from the University of Virginia in 1971, retired after 26 years at Varian Medical Systems, and currently serves as Lecturer in physics at Northern Kentucky University in Highland Heights, KY.