In addition, the presence of two different genetic lineages in the same ancient grave suggests that the population of Ice-Age Alaska was more diverse than previously believed. It also appears to support the idea that migrants across the Bering Strait remained in the local region (Beringia) for some 10,000 years before moving southwards—a theory known as the Beringian Standstill hypothesis. According to this version of events, humans were able to thrive in Beringia even at the height of the Ice Age, as the region remained tundra with sparse vegetation. Glaciers blocked access to the rest of the Americas, however, until around 15,000 years ago, when their melting put an end to the standstill.