For thousands to millions of years, tiny marine plankton called foraminifera, or forams, have built spiral shells that twist either to the left or the right. These microscopic organisms are found in vast numbers in the world’s oceans, and their shells are crucial for understanding Earth's past climate and environments. However, fossil records reveal that these creatures have occasionally changed the direction in which their shells spiral, switching back and forth over time. Scientists have been studying this phenomenon since the 1950s, when they first noticed these changes in layers of seafloor sediments. Some species of forams show a strong preference for one spiral direction, with up to 97% of individuals in a species coiling in the same way. Occasionally, a new coiling direction becomes dominant across the oceans at the same time. In the 1950s, David Ericson observed that the species Neogloboquadrina pachyderma coiled to the left in cold climates during ice ages and to the right in warmer periods. However, later genetic research revealed that this species is actually made up of two distinct species, each with its own preferred coiling direction. This finding challenged the earlier idea that temperature was the main driver of these changes. In 2013, Yurika Ujiié found that the direction in which different foram species coiled their shells did not match up with temperature patterns, further disproving the earlier hypothesis. More recent studies suggest that the flipping of shell coiling directions might be an accidental sign of major evolutionary events, where a new trait spreads across vast ocean basins. Bridget Wade and her team examined coiling patterns in several planktonic foraminifera species over the past 56 million years and found evidence of flipping across multiple ocean basins and climate zones. For example, Paragloborotalia siakensis changed from having a mix of coiling directions to being almost entirely left-handed 15 million years ago. Another species, Globorotalia scitula, flipped its coiling direction twice over the same period. One species, Pulleniatina obliquiloculata, has an unusually detailed fossil record showing that it has coiled almost exclusively to the right for the past 860,000 years. Before that, it experienced rapid, global changes in shell coiling direction every few thousand years. These shifts were too sudden and widespread to be explained by slow, gradual evolution. Scientists are now considering the possibility that a hidden or "cryptic" species, which may have a significant adaptive advantage, could have spread globally. This species might have been carried by ocean currents and its own success, leading to one coiling direction becoming dominant. Some researchers, like Kate Darling, suggest that these flipped forams might represent a new species or a genetic variant that outcompeted others. Julie Meilland, who studies reproduction in live forams, noted that the ratios of coiling directions in her laboratory cultures do not always match what is found in the fossil record. This suggests that the factors influencing coiling direction could be complex, involving not just genes and evolution, but also the environment and even chance. While the near-simultaneous global shifts in foram coiling might seem mysterious, some researchers suggest that what appears instantaneous in the fossil record could actually take place over thousands of years. During this time, ocean currents circulate around the globe, potentially speeding up the spread of a new genetic variant across the planet.