I have been working on a little-known text, the Paraphrase of Shem, while doing research for an article I'm writing called "After the Gospel of Judas: Reassessing what we have known to be true about Cain and Judas." What has struck home for me about this text is just how "weird" it is to modern readers, myself included, yet how "advanced" it must have been at the time it was written.
This text is what I'm calling "wombic Gnosticism" since it relies on a mythology of three divine principles and a Womb which births everything - angels, demons, the cosmos. The text is very erotic, with sexual images everywhere, used to explain how this cosmos came into being.
What is so fascinating about this text is that its mythology is based on second century scientific knowledge about embryology. What the author is doing is taking the most advanced scientific knowledge about conception and the formation of embryos and he is using it to explain religious questions. This is a person who was on the cutting edge of science and religion in the second century.
So the Gnostics appear to me to be the ones who were trying to combine "secular" knowledge of the second century - whether it be middle Platonic philosophy or Soranus' embryology - with Judaism and Christianity. In sociological terms this is interesting because what it means is that they were not forming sects or cults. Rather they were taking a religious "sect" (i.e. Christianity) which was defining itself by removing itself from society's ways, and reforming it so that it was more friendly to society, so it fit in to society's ways. This is a tendency that sociologists track. Often sects and cults define themselves against society. But overtime, this erodes and there are people within the movement that want to belong to society again. So the movement is reformed. This appears to me to be what was happening with the ancient Gnostics.
At any rate, this is a topic that I am collecting evidence for to write another paper about the origins and growth of Gnosticism.