Anton Petrov discusses the mystery of the Mid-Pleistocene Transition (MPT), which occurred about a million years ago and caused ice ages to become longer and more extreme. The source explains that the initial cycles of glaciation, lasting 41,000 years, were probably caused by Milankovic cycles, but later, around the MPT, the cycles lengthened to 100,000 years, and temperature fluctuations increased dramatically. Recent research suggests that this dramatic increase in the intensity of ice ages was not caused by a cosmic catastrophe, but by a gradual change in the North Atlantic seafloor that made the ice adhere more easily to the substrate. The hardening seafloor, a result of earlier glaciations, led to the formation of much larger glaciers, which then disrupted ocean currents, exacerbating global cooling. The material also mentions another possible cause of the planet's initial cooling some 2.5 million years ago, which could have been a nearby supernova.