For years, archaeologists studying Southeast Asia have been puzzled by the “missing millennium”, which took place between 6,000 and 4,000 years ago, with little sign of human settlement. According to a study published in the journal Nature Communications, archaeologist Joyce White believes the settlements may have disappeared because a drought forced people to look elsewhere for water.
To recreate the climate of that era, White and colleagues surveyed stalagmites in a cave in northern Laos. By analyzing the rock content of this slow deposition, the researchers were able to measure not only its age, but also how wet it was at the time.
The researchers found that rainfall in caves was relatively stable for more than 4,000 years, and then suddenly declined about 5,100 to 3,500 years ago. This suggests that the region may have experienced a prolonged drought that lasted more than 1,000 years.