Rapid climatic shifts and its influence on ancient civilisations: Evidence from marine records

Abstract

The southwest (SW) monsoon system in the Arabian Sea exerts a strong influence upon the climatic conditions in South and Southeast Asia and the associated monsoon rainfall has a great impact on the socio-economic and agricultural development in the densely populated South Asian region. Studies on the variability of the SW monsoon for the last 19,000 years before present (BP) by using marine sediment records reveal that the SW monsoon started its intensification from 12,000 years BP after a weak phase during the last glacial period. During the Holocene period, the weakening of the SW monsoon stated from 5,000 years BP and the intensity of monsoon returned to glacial strength at 3,500 years BP coinciding with the onset of arid climate elsewhere in the tropics. The onset of weak phase of the monsoon and arid climate at 3,500 years BP appears to be a primary reason for the decline of the Indus Valley Civilisation, major changes in vegetation along the Western Ghats and decrease of river discharge from all major rivers during that period. Similarly, the Classic Maya Civilisation of Central America collapsed around AD 750-900 due to rapid climatic change during that period in Central America. These evidences suggest that climatic changes have a bearing on ancient civilisations and human heritage