The Pleistocene spans a period from around 2.5 million years ago to just over 12,000 years ago, and it was an epoch of enormous change on Earth, mainly characterized by climate changes involving fluctuations between periods of extreme heat and long periods of glaciation. This period is commonly known as the Ice Age, despite the fact there were actually a number of separate periods of cold.

Along with the climate challenges, this was also the period that saw the development of modern humans. The origin of our ancient ancestors is still a matter of debate amongst paleontologists, and classification systems for early hominoids are constantly being updated as new discoveries are made. What is generally agreed upon is the species Homo sapiens belong to the order primates and the sub-order anthropoids. Within the anthropoids sub-order, humans belong to the family hominids, which also includes other animals such as the orangutan and the great apes. Drilling down even further, humans belong to a sub-group of hominids known as hominin. The sub-group hominin includes humans, as well as chimpanzees and gorillas.

Discoveries have revealed more than 20 species of the genus Homo, all of which appeared during the Pleistocene Epoch, and all but Homo sapiens became extinct during the same period. The challenge is understanding which of these groups are predecessors to Homo sapiens, and which are separate groups that died out leaving no current representation. Not knowing this information makes it difficult to determine neat classification and establish precisely when hominins separated from the rest of the non-hominin primates.

The cold Pleistocene temperatures lowered water levels across the planet, exposing land that was not there before or after the period. At the same time, significant regions of the planet were very different during the Pleistocene, including Southeast Asia, particularly the modern islands of Bali, Borneo, Sumatra, and the Malay Peninsula, roughly equivalent to parts of Indonesia, Malaysia, Myanmar, and Thailand. This region, which modern scholars refer to as Sunda or Sundaland, was unique because all of it was connected by land, meaning today’s islands were once part of a contiguous subcontinent, and in terms of the people, flora, and fauna, it was very different than it is today. If a modern traveler could somehow transport back to the Pleistocene, Sundaland would look nothing like modern Southeast Asia, and would resemble as much of a lost world as something out of a science fiction novel.

Although much is still unknown about Sundaland, researchers have uncovered plenty of evidence bringing this lost world to life. As anthropologists and archaeologists developed new models and discovered ancient material culture, they learned that Sundaland played a significant role in the development of Neolithic Southeast Asia in many ways. The rise of the ocean spurred Sundaland’s inhabitants to find new, innovative ways to survive, ultimately laying the groundwork for the population of another ancient subcontinent known as Sahulland or Sahul. Sahul is the modern name for the subcontinent, including Australia and New Guinea, which, like the lands in Sunda, were connected due to the lower sea levels. When the first inhabitants from Sunda arrived in Sahul about 50,000 years ago, it was the equivalent of the Apollo 11 flight, the Vikings’ settlement of Vinland, or Christopher Columbus’s maiden voyage to the Western Hemisphere. Although they did not know the repercussions of their voyages, the first migrants from Sundaland to Sahulland helped propel humanity from the Paleolithic Period into the Neolithic.