Continuity of microblade technology in the Indian Subcontinent since 45 ka: implications for the dispersal of modern humans

Abstract

We extend the continuity of microblade technology in the Indian Subcontinent to 45 ka, on the basis of optical dating of microblade assemblages from the site of Mehtakheri, (22° 13' 44″ N Lat 76° 01' 36″ E Long) in Madhya Pradesh, India. Microblade technology in the Indian Subcontinent is continuously present from its first appearance until the Iron Age (~3 ka), making its association with modern humans undisputed. It has been suggested that microblade technology in the Indian Subcontinent was developed locally by modern humans after 35 ka. The dates reported here from Mehtakheri show this inference to be untenable and suggest alternatively that this technology arrived in the Indian Subcontinent with the earliest modern humans. It also shows that modern humans in Indian Subcontinent and SE Asia were associated with differing technologies and this calls into question the "southern dispersal" route of modern humans from Africa through India to SE Asia and then to Australia. We suggest that modern humans dispersed from Africa in two stages coinciding with the warmer interglacial conditions of MIS 5 and MIS 3. Competitive interactions between African modern humans and Indian archaics who shared an adaptation to tropical environments differed from that between modern humans and archaics like Neanderthals and Denisovans, who were adapted to temperate environments. Thus, while modern humans expanded into temperate regions during warmer climates, their expansion into tropical regions, like the Indian Subcontinent, in competition with similarly adapted populations, occurred during arid climates. Thus modern humans probably entered the Indian Subcontinent during the arid climate of MIS 4 coinciding with their disappearance from the Middle East and Northern Africa. The out of phase expansion of modern humans into tropical versus temperate regions has been one of the factors affecting the dispersal of modern humans from Africa during the period 200-40 ka.

Figure 1. Radiocarbon dated microblade sites in the Nimar region of Madhya Pradesh in the Indian Subcontinent.

Figure 2

1. MIS 6 : Modern humans and possibly other archaics in Africa. Neanderthals in Europe and Denisovans in Central and Eastern Asia, Indian archaics in the Indian Subcontinent and Sundaland. Equatorial forest zone of SE Asia might not be occupied by hominins. 2. MIS 5: Expansion of modern humans throughout the Tropical and Subtropical zone. Indian archaics retreat from Sundaland which is mostly submerged due to higher sea level. 3. MIS 4: Neanderthal expansion into Middle East at the expense of modern humans and possibly to west. Denisovans might have become extinct at this time. Desert zone of Africa and Asia abandoned by hominins. Archaic Indians disappear with the entry of modern humans into the Indian Subcontinent. 4. MIS 3: Indian Subcontinent a major source for expanding modern humans. Archaic populations disappear with some admixture with modern humans.

Figure 3. Location of sections at Mehtakheri.

Figure 4. Mehtakheri excavation 2009 showing layers 1-26.

Unit 2, containing the artifacts is layers 18-26. Erosional contact between Unit 1 and 2 marked by sand layer above layer 18.

Figure 5. Mehtakheri excavation 2009 showing further excavation exposing Unit 3.

Position of dated samples MHK 10-14: were sampled can be seen. Boundary between Unit 2 and 3 marked by change in colour due to reduced calcrete in unit 3.

Figure 6. Stratigraphy and position of dated samples and artefacts in Sections 1 and 2.

Artefact frequency is shown to the left of the sections.

Figure 7. Section 3 showing the position of the dated samples.

Boundaries between individual beds are shown.

Figure 8. Decay curve for one of the sample.

Figure 9. Growth curve for MHK-09-09 sample.

Figure 10. Microblade industry from Mehtakheri: M 25and F 1: Microblade cores; J4, XX4, A 1: backed blades; M 18: crested guiding ridge flake, E 15 and M 13 blades; G 5 & C 26 broken blades.

XX4 is a complete example of J4. J4 is from the excavation while XX4 is from surface collection close to the excavated section.

Figure 11. D3, F1, M25, J15 and M23 are microblade cores.

J39 is a trimmed nodule. J2 is is a retouched flake on multicoloured chert and M9 is a perforator made on a platform rejuvenation flake. J44, D107, A42 and I41 are hammerstones of various sizes. C26, D26, D78, C3 are broken flakes and M22 and M13 complete flakes. K1 and M2 are from the initial stages of core reduction showing the much larger initial size of the cores. M 2 also retains a part of the crested guiding ridge.

Figure 12. Size distribution of broken and complete blades from Mehtakheri 2009.

Figure 13. Size distribution for flakes from Mehtakheri 2009.