1) Was there available access to significant quantities of high-quality, fine-grained stone for tool production in these areas east of the Movius Line? Obviously, blade technology is quite dependent on fine-grained stone such as flint, chert, obsidian etc. Furthermore, did hominin populations rely on locally-sourced materials, such as wood or bamboo, for tool manufacture.

2) What are the specific functions for this stone tool technology? For instance, if the initial colonisation followed a costal route, then these technologies may have needed to adapt for the exploitation of coastal resources.

3) Lastly, there are the issues of demography and the potential role of serial founder effects as relatively small population units migrated eastward. Do we see instances where serial founder effects not only operate on the genetic features of populations, but in addition leads to a loss in the complexity and diversity of cultural and technological patterns as the result of an increasing distance from the demographic point of origin?

As for the point about those Flores hominids: I don’t know enough about them to really make an informed comment. For the moment though, I’d say that having a small population is not the only factor. If they had a sufficient level of density, then this may have led to stronger and more regular instances of social interconnectedness. So, as the probability of encountering increases, so does the ability to maintain certain forms of technology.

It’s been said that the lack of raw materials and low quality of the material was a restraining factor on Levallois, but I guess the only progress in this field is actually dependent on findings of another field, genetics, which can at least in theory let us know which way(s) modern and prehistoric populations arrived into East Asia, either via Central Asia which seems to have Levallois or via the southern coastal route which seems to have forgotten it.

“particularly since they should derive some or most of their ancestry from Africa/West Asia.”
Only some? I agree that shoveled incisors are perhaps a trait “Mongoloids” got from erectus, but the erectus component overall should be very low based on what we know from genetics. Not one phylogenetically-distant sample of mtDNA and Y-Chromosome have been discovered yet. All fall into a sub-set of East African/Eurasian lineages.
My theory on how the above seemingly contradictory situation can happen is this:

1. The erectus admixture must’ve occurred in a very small population.
2. The uniparental markers died out in this bottleneck but the autosomal genes remain.
3. The shovelling trait was selected in severe ecological conditions.
4. This “Mongoloid” population at some point started to expand exponentially.

It’s interesting how population genetics has moved the orthodoxy in a less politically correct direction toward the fundamental division being sub-Saharan Africans vs. Eurasians.

The question is, if there’s some optimum, why don’t people make the same tools everywhere? And you’ve got four possible answers:

(1) Different optima; different ecological contexts or raw material availability require different tools.

(2) Transmission is too hard to keep going in these populations.

(3) Path-dependence: slightly different starting points may lead to very different technical developments.

(4) Relative neutrality: It just doesn’t matter very much which tools you use.

Path-dependence is probably the most common explanation for why Levallois is rare in China — the idea being that you don’t develop prepared cores easily if you aren’t starting from a large cutting tool tradition. What isn’t easily explained is why sites after 50,000 years ago should be susceptible to this same path-dependence — particularly since they should derive some or most of their ancestry from Africa/West Asia.

Personally, I keep coming back to ecology. For two traditions relatively late in the record and possibly synchronous (although I hesitate to assume this until a better chronology emerges), I tend to go with Binford — they’re probably doing different things.

Oh, and there are those Flores hominids, making tools for hundreds of thousands of years in a tiny population, and Java periodically cut off from SE Asia. Toolmaking seems like it wasn’t very easy to lose.