Sri Lanka is an island off the southern tip of India. There is secure evidence of settlements in Sri Lanka by 130,000 years ago, probably by 300,000 BP and possibly by 500,000 BP or earlier. Palaeo-environmental investigations indicate that interglacials correlated with increased atmospheric activity over the island - which was manifested in correspondingly increased rainfall on the windward aspect of the central mountains and increased desiccation on the leeward side due to the drying foehn effect of katabatic winds. This model has been transposed to the eight major ecozones of the country with their respective prehistoric carrying capacities fluctuating in phase with climatic shifts. Population densities in these ecozones have been estimated for the Quaternary on the basis of ethnographic analogy. Subsistence strategy has also been assessed through archaeological evidence against a backdrop of ethnographic analogy and postulated biotic resources that would have been available for exploitation by Quaternary foragers.
At the commencement of the 1st millennium BC, there are indications of a rapid transition from a geometric microlith-using Mesolithic culture to the Early Iron Age, with horse, cattle, pottery and paddy cultivation. It is proposed that with iron technology (for clearing hitherto intractable equatorial rainforest) a greatly enhanced food production capability increased carrying capacity several-fold, thus attracting long distance links with India. The latter possibly involved migrations, of which the Indo-Aryan Sinhalese language (which was in use in Sri Lanka since at least 500 BC) could be but one manifestation.