[tspike]

You could replace the word "advanced" with "unsustainable" and the thought still holds.

[kragen]

No, unsustainable societies like the Lykov family or the Tasmanians were also often unspecialized. I suspect that specialization improves sustainability in general, at least up to a point. But it depends on how it's structured. The Khwarezmian empire had a high degree of specialization for the time, but one bad decision by the emperor made it unsustainable.