“Seth material” search engine (Jane Roberts)

Large groups, however, simply left their cities, destroyed the force fields that had enclosed them, and joined the many groups of relatively uncivilized peoples, mating with them and bearing children. These Lumanians died quickly, for they could not bear violence nor react to it violently. They felt however, that their mutant children might have a resulting disinclination toward violence, but without the prohibiting nerve-control reactions with which they were endowed.

Their vast technology and their great civilization was largely underground. They were, in those terms, the original cavemen, and they came out from their cities through caves also. Caves were not just places of protection in which unskilled natives squatted. They were often doorways to and from the cities of the Lumanians. Long after the cities were deserted, the following natives, uncivilized, found these caves and the openings.

In the period that you now think of as the Stone Age, the men you think of as your ancestors, the cavemen, often found shelter not in rough naturally formed caves, but in mechanically created channels that reached behind them, and in the deserted cities in which once the Lumanians dwelled. Some of the tools fashioned by the cavemen were distorted versions of those they had found.