An interesting new paper extends continuity of microblade technologies in India to ~45ka, and hence makes it probable that these were introduced by AMH together with the UP colonization of the rest of Eurasia.
I am not sure that the authors' suggestion that early modern humans were "tropically adapted" is certain. Personally, my idea du jour is to derive them from the Saharo-Arabian belt. In any case, as an advocate of "early OOA" (in the sense of pre-UP/LSA), it makes sense to me that modern humans in Eurasia would be initially climate-limited and at a disadvantage vis a vis archaic Eurasians inhabiting regions for which they were maladapted. In my opinion, it was the technological revolution of ~50ka being responsible for the extension of their range at the expense of other Eurasians.
PLoS ONE 8(7): e69280. doi:10.1371/journal.pone.0069280
Continuity of Microblade Technology in the Indian Subcontinent Since 45 ka: Implications for the Dispersal of Modern Humans
Sheila Mishra et al.
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.