Study: Rising sea level 26,000 years ago prompted migration between South, Southeast Asia.

A new study found that early settlers in the region of Southeast Asia were forced to relocate to South Asia after sea levels began to rise, affecting the coastal landscape of the region some 26,000 years ago. This discovery was made possible by the findings of the study.

A group of researchers from Nanyang Technological University (NTU) in Singapore looked into historical evidence that suggested rising sea levels affected populations living in the Malay Peninsula, islands of Sumatra, Borneo, and Java, all of which were originally a part of a large landmass known as The Sundaland. Their findings were published on Saturday in the journal Nature.

In a press release, Kim Hie, an assistant professor at NTU's Asian School of the Environment and the principal investigator from the Singapore Center for Environmental Life Sciences Engineering, discussed how the findings underlined the effects of environmental changes on human history and migration.

Changes in the environment have had significant effects on the course of human history, including the migration, growth, and dispersion of populations. However, how changes in the environment can affect the genetic makeup of populations is a topic that receives less attention. Our research is the first time anyone has documented data that rising sea levels altered the genetic make-up of human populations in Southeast Asia, a legacy that continues to have an effect on contemporary populations.

According to the study, the group created paleogeographic maps of South and Southeast Asia by using sea level data ranging from 26,000 years ago to the present day. The data was used in the construction of the maps.

The scientists from NTU discovered, through the use of paleogeography, which is the study of historical physical landscapes, that the sea level in South and Southeast Asia rose to 130 meters (approximately 427 feet) between the period of the Last Glacial Maximum (which occurred about 26,000 to 20,000 years ago) and the mid-50 Holocene. This was approximately 427 feet higher than it is today (approximately 6,000 years ago).

In addition to the paleogeographic maps, the NTU team used population genetics in their research. The team used whole-genome sequence data that was produced by GenomeAsia 100K, a non-profit company that was founded in 2016 and is hosted by the university.

After that, the scientists studied genetic data of high quality from 59 different ethnic groups that were indigenous to South and Southeast Asia 50,000 years ago. Scientists from NTU were able to draw conclusions about the genetic origin and demographic history of the groupings by using the information provided, which included details such as the groups' location and population size.

NTU scientists were able to pinpoint two periods of rapid sea level rise using these methods. During these times, a portion of the region was submerged by water, and the landmass was divided into a number of smaller islands. This resulted in the population of Sundaland being split into a number of smaller groups.

The team also discovered that the temperature started to rise from the Last Glacial Maximum, which created an environment that was favorable for human population growth. This resulted in a population density surge in the Island Southeast Asia region that was at least eight times higher than it was during the time of the Last Glacial Maximum.

According to the research, the overpopulation that ensued as a direct consequence of the rising sea level and temperature compelled people to relocate their communities further inland, to mainland Southeast Asia and South Asia.