The　emergence　of　high-resolution　proxy　records　from　the　Asian　monsoon　region　suggests　that　the　monsoon　system　is　bistable　and　can　abruptly　transition　between　a　suppressed　and　active　state.　This　observation　is　critical　in　considering　how　the　monsoon　system　may　have　influenced　the　development　of　societies　across　South　and　East　Asia　during　the　Holocene.　Using　a　new　high-resolution　(similar　to　5　years/sample)　speleothem　stable　isotope　record　from　northeast　India　that　spans　the　early　and　mid-Holocene,　a　number　of　abrupt　changes　in　the　oxygen　isotopic　composition　of　precipitation　(delta　O-18(p))　are　documented.　The　most　dramatic　of　these　events　occurred　similar　to　4000　years　ago　when,　over　the　course　of　approximately　a　decade,　isotopic　values　abruptly　rose　above　any　seen　during　the　early　to　mid-Holocene　and　remained　at　this　anomalous　state　for　almost　two　centuries.　This　event　occurs　nearly　synchronously　with　climatic　changes　documented　in　a　number　of　proxy　records　across　North　Africa,　the　Middle　East,　the　Tibetan　Plateau,　southern　Europe,　and　North　America.　We　hypothesize　that　the　excursion　could　represent　a　shift　toward　an　earlier　Indian　Summer　Monsoon　withdrawal　or　a　general　decline　in　the　total　amount　of　monsoon　precipitation.　The　new　record　provides　a　very　significant　advance　with　respect　to　age　control　and　sample　resolution　of　terrestrial　climate　change　over　South　Asia　during　this　period　when　a　number　of　major　societal　changes　occurred.　While　evidence　of　a　causal　relationship　between　climate　and　the　reorganization　of　the　Indus　Valley　and　Old　Kingdom　Nile　civilizations　is　beyond　the　scope　of　this　study,　the　tight　age　constraints　of　the　record　show　with　a　high　degree　of　certainty　that　much　of　the　documented　deurbanization　of　the　Indus　Valley　at　3.9　kyr　B.　P.　occurred　after　multiple　decades　of　a　shift　in　the　monsoon＇s　character　but　before　the　monsoon　returned　to　its　previous　mid-Holocene　state.