Population increase and environmental deterioration correspond with microlithic innovations in South Asia ca. 35,000 years ago

Abstract

Genetic studies of South Asia's population history have led to postulations of a significant and early population expansion in the subcontinent, dating to sometime in the Late Pleistocene. We evaluate this argument, based on new mtDNA analyses, and find evidence for significant demographic transition in the subcontinent, dating to 35-28 ka. We then examine the paleoenvironmental and, particularly, archaeological records for this time period and note that this putative demographic event coincides with a period of ecological and technological change in South Asia. We document the development of a new diminutive stone blade (microlithic) technology beginning at 35-30 ka, the first time that the precocity of this transition has been recognized across the subcontinent. We argue that the transition to microlithic technology may relate to changes in subsistence practices, as increasingly large and probably fragmented populations exploited resources in contracting favorable ecological zones just before the onset of full glacial conditions.

Fig. 1.

Distribution of Indian haplogroup (hg) M subclades age estimates (bar graph), with a peak 35–28 ka ago indicating a locally derived demographic event at this time. A second, larger population expansion is seen following the Last Glacial Maximum and continuing into the Holocene. Also shown are the regional hg M coalescence times for India, East Asia, and Oceania, with means (circles) and standard error range. The Indian coalescence date is anomalously young, as a result of the later significant deviations from a random demographic expansion history.

Fig. 2.

South Asia, showing reconstructed vegetation zones for ca. 30 ka ago and location of microlithic sites. Sites indicated by letters are as follows: A, Jurreru Valley; B, Patne; C, Sri Lanka caves, from north to south Beli-lena Kitulgala, Batadomba-lena and Fa Hien; and D, Sri Lanka coastal sites 49 and 50. Vegetation zones indicated by numbers are as follows: 1, desert and semidesert (Caligonum-Salvadora-Prosopis-Acacia and scattered grasses); 2, savannah and tropical dry deciduous woodland mosaic (Acacia-Anogeissus-Terminalia, Hardwickia in some localities, abundant gatherable grasses and legumes); 3, dry deciduous woodlands, including teak; 4, dry deciduous woodlands, including Shorea-Hopea; 5, deciduous Shorea-Hopea woodland and grassland/marsh mosaic; 6, moist deciduous and scattered evergreen taxa; 7, Tropical evergreen and semievergreen forest refugia; 8, tropical/subtropical mountain forests.

Fig. 3.

Lithic technology in the Jurreru Valley. Note the major technological change between 38 and 34 ka from single and multiplatform cores with scrapers, blades, and burins to an assemblage dominated by microblades, microblade cores, and backed artifacts (indicating systematic microlith production). Percentages are proportions in relation to the total artifact assemblage in strata (Locality 9) or in above-ash contexts (Localities 3, 21, and 23).

Fig. 4.

Stone artifacts from the Jurreru Valley. (A) Middle Paleolithic artifacts from Locality 23. (B) Microlithic cores and artifacts from Locality 9, with other artifact forms from the site. All scales are in cm.