Science, being a field that runs on the lifeblood of its researchers and fact-finders, doesn’t always hit its mark on its first time around the bend. As the fields that comprise it run on the common ground of truths accepted by its individual experts or governing bodies—proven and tested through rigorous, repeated experiments and tests—new studies that reveal new truths about the world often come under intense scrutiny to either prove or disprove its claims. Such is especially the case when studies attempt to answer science’s greatest questions.
One particular question of such a type is the origins of avian magnetoreception, or how birds sense the Earth’s magnetic field. Migratory birds employ different tools to help them cover the vast distances they fly yearly during their great migrations, one of which being their ability to “sense” magnetic fields to let them know where they’re going. It’s pretty much been a mystery to scientists ever since it was first described; a particularly long migration on record was by an Arctic tern that traveled nearly 22,000 km (14,000 mi) to travel from the Fame Islands, off the east coast of Britain, to Melbourne, Australia. Currently there are two famous hypotheses as to how birds manage to do this feat: either by the reaction of magnetite particles somewhere within their bodies, or by a “chemical compass” based on a radical pair mechanism.
A radical pair mechanism, in the context of avian magnetoreception, attempts to explain birds’ “magnetic sense” as a result of them being capable of detecting how these magnetic fields react to the correlated “spins” of unpaired electrons on a pair of radicals. These radicals are formed by proteins in their eyes that are sensitive to light, such that they change into their radical forms and “pair” with another protein that underwent a similar process through exposure to light. Researchers from the University of Oxford and the University of Oldenburg seem to have demonstrated this effect by isolating a protein called cryptochrome 4 (Cry4), gathered from the eyes of migratory European robins (Erithacus rubecula). The study was published in Nature.
In it, the scientists isolated the protein in question and performed several analyses, including computer simulations and spectroscopic tests. These tests and simulations show that Cry4 does, indeed, form radical pairs in a light-dependent reaction that were sensitive to magnetic fields; they even tested the same protein gathered from nonmigratory birds like chickens and pigeons, and showed that the pairs formed from these particular Cry4 proteins weren’t as sensitive as those from the robins, further adding to their hypothesis that the robin Cry4 was “particularly specialized for magnetoreception.”
Several scientists weren’t so immediately warm to their findings, though. Some of them point out that the study in question omits some context for its findings, and that their results don’t necessarily show Cry4 as the answer they’ve been looking for for their magnetoreception problem. According to magnetoreception researcher Rachel Muheim, from Lund University and unrelated to the study in question, there are a number of results from previous experiments that “can’t be explained” by the mechanism that the researchers of the new study proposed. A particular point of contention is the fact that the radical pair mechanism described in the new study is known not to work under green light, despite previous studies reporting from behavioral experiments that robins and other birds can orient themselves just fine under green light. Ultimately, further research is needed to confirm—or deny—the results proposed by this study.
Ultimately, while the study has provided valuable data about how Cry4 functions in birds, researchers must take everything with a grain of salt. As is often the case with new scientific discoveries, new results necessitate testing and scrutiny. Scrutiny leads to further investigation, which calls into question the integrity of the methodology performed. This is why scientific discoveries often take so long to actually be announced: it’s not a matter of finding it the first time—it’s a matter of finding the same result, every single time, when done in the same way. The reproducibility of a scientific experiment is what lends it credibility, and pushes it forward towards scientific consensus. This avian study, much like every other study in any field, must push through this rigorous screening process before being accepted by the researchers’ peers. It’s this unbroken chain of repeated testing and reproduction of results that lead to theories and laws that end up in school lectures and textbooks today. And if, just like this study, we wish to find out more about the world around us, we need more than one look into its inner workings in order to truly figure things out.
Bibliography
- Offord, C. (2021, June 23). New Study Fuels Debate About Source of Birds’ Magnetic Sense. The Scientist. Retrieved August 30, 2021, from https://www.the-scientist.com/news-opinion/new-study-fuels-debate-about-source-of-birds-magnetic-sense-68917
- Xu, J., Jarocha, L., Zollitsch, T., Konowalczyk, M., Henbest, K., Richert, S., … & Hore, P. (2021). Magnetic sensitivity of cryptochrome 4 from a migratory songbird. Nature.
