A clear statement description of the way that human consciousness has changed throughout recorded history (and inferred from pre-history) is something I associate with Rudolf Steiner and his later follower Owen Barfield; who both explained it in terms of each human being having undergone multiple reincarnations. The changing nature of consciousness was therefore assumed to be caused by the accumulated experience and learning - hence maturity - of the reincarnating spirit.
Ultimately, the underlying cause of these assumed multi-reincarnational changes was tacitly assumed to be the divine will; which sought to provide multiple and additive experiences to spirits.
This was supposed to operate by a process that starts with pure (immaterial) spirit beings, leads down into denser and denser incarnations (such as ourselves), and ultimately (as its highest goal) leads back up to purely spiritual existence.
But I do not share these assumptions about reincarnation.
More importantly I regard Jesus Christ as having provided Man with the opportunity of resurrected human life in Heaven - which is a permanent state of embodied incarnation.
In short: as of 2025 (and for nearly 2000 years) God does not want us to reincarnate after death - but instead to follow Jesus Christ to resurrected eternal life in heaven.
Thus, for me, the objective of spiritual development is not a "spiritual being"; but instead a resurrected and embodied Man, of which the model was the resurrected Jesus.
However, since I regard the evolutionary development of Mankind as a reality, but reject the Steiner/ Barfield explanation; I feel a need to explain this in terms of causality. I believe that there are several interacting causes, working at different levels. What follows is my current understanding.
1. God's plan
At the deepest level of causation; I believe that God (our Heavenly Parents) desires that divine creation should lead first to divine children, and then towards the idea of "divine adults" - God seeks to encourage childlike children to develop into grown-up friends.
(Much as it is usual (but with significant exceptions) to expect and hope that our own mortal children will not remain immature and childlike; but will grow-up to make the choice to become "best friends" with their parents.)
In other words; divine creation is structured towards the generation of God's children - such as we now are; and that we children should be enabled and encouraged to "grow up" further, in order to mature towards becoming beings of the same kind and level as our Heavenly Parents.
In yet other words; God desires that we would (through time) choose to develop towards becoming fully divine, fully loving, creators - and then to participate in the eternal work of divine creation. It was Jesus Christ who first achieved this, and who made it possible for others to follow Him in this.
The goal is that our Heavenly Parents should cease to be the only beings at their level of divinity, but should build a continually growing family of grown-up children of God (together with the extended family of those beloved children who - whether by spiritual nature or current-choice - remain spiritually "immature": i.e. not full-creators.
2. Incarnation of progressively more mature spirits
One of the ways that God influences the direction of creation, is through the nature of pre-mortal spirits that are incarnated into mortal life on earth.
My impression is that when the earliest-known Men were first incarnated, their consciousness was more like that of young children. And incrementally throughout history, progressively more-grown-up spirits were incarnated; who tended to mature towards what we would now recognize as more adult modes of consciousness.
So, at present and overall, spirits are incarnated that spontaneously mature to a kind of spiritual adolescence - beyond which further maturation depends on various individual factors, including personal will and choices.
(I suspect that while spiritual maturation from childhood to adolescence is mostly spontaneous and involuntary; maturation beyond spiritual adolescence can only ever be attained by active alignment with God's nature and creative will, and by personal choice - the choice to live only by love.)
Maturity is most obviously revealed in terms of thinking and self-awareness... Modern Men are aware of our-selves and the distinction from the world and others; and we live subjectively in our stream of conscious thoughts - in ways that did not happen (or only in rare individuals) in the past.
3. Metaphysical assumptions and ideology
Due to the nature of the human society into-which modern humans are born (which is partly a consequence of past and present choices by other people; under the influence of demonic beings) - modern Men assume that ultimate reality is dead (unalive), material (not spiritual); and operates solely by physical-mechanical causes or non-causally/ chaotically (ie. "randomly").
I believe that these bottom-line assumptions concerning reality have a profound and malign effect on modern Man's consciousness.
What this typical modern metaphysics does to our consciousness; is to transform self-awareness into a false conviction of inescapable existential alienation - the implicit yet wrong belief that we are alone in our thinking, which is merely subjective: detached from reality.
And this leads onto the typically modern mind-set of existential despair; variously countered by the attempt to overwhelm it with hedonism, and/or to obliterate thinking by such means as constant distraction by powerful stimuli, strong emotions, intoxication, and the like.
In sum: an element in the changing of consciousness is the prevalent ideology of our times. And in more general terms, it would be expected that metaphysics, theology, and ideology would often (although not necessarily) tend to shape human consciousness in particular directions - which is, of course, exploited as much as possible by the purposive powers of supernatural evil.
4. Direct spiritual contact between people, and other beings
I believe that there is potentially a direct (mind-to-mind, as it were) contact between living people, between the living and some of those who have died, and other beings.
Insofar as this happens (for instance, among those people in mutually-loving relationships) among people whose consciousness's are changing for the reasons described above; this is the basis for shaping, perhaps amplifying or instead reversing, changes in consciousness that may be directional through time.
Put differently; we each inhabit a very selective thought-world - one that changes throughout our lives, and includes new, different, other-minds (alive, dead, or potentially not human).
This, then, is another reason for changes in consciousness.
5. The comfort and guidance of the Holy Ghost
The Holy Ghost is a potential source of comfort and guidance for those who follow Jesus, and this contact naturally affects a human consciousness and its development through time.
Such interaction with the Holy Ghost has the nature of a chosen, mutual, and specific relationship between one spiritual Being and another.
Which means that I disagree with those who conceptualize the Holy Ghost as providing some kind of blanket effect on Mankind, or any particular group of people.
(I also disagree with those who regard the evolution of consciousness as driven by any kind of quasi-physics-like influence on the planet and its inhabitants... I mean those who see the maturation of consciousness as driven by an externally-applied influence - such as increasing frequency or vibrational level; or some kind of transformation of spiritual force, or an increase in spiritual energy; or indeed by astrological change.)
As a general comment - I think it is probably necessary to emphasize (to myself, if not other others!) that the causal mechanisms that contribute to the developmental evolution of human consciousness, are all aimed at the individual human spirit.
I am increasingly sure that God does not, and never has, operated primarily at the level of human groups.
We ought therefore to try and stop thinking habitually about Men In The Mass; when it comes to understanding fundamental spiritual matters.
The false-impression that God is concerned primarily with the salvation of particular tribes or particular churches; was I think an (inevitable) artefact of an earlier stage of human consciousness; among Men who (inevitably - but with some few exceptions) experienced reality in this groupish way.
That is to say: The earlier we go in history, the more groupish was human consciousness - and individuals were not, and did not feel nor aspire to be, detached from the "group mind".
But as of Now - things are very different. From adolescence onward, modern people are spontaneously detached from the group mind, and must therefore be influence and controlled ("micro-managed") by multiple and constantly-applied external and perceptual inputs - laws, rules, propaganda etc.)
Nowadays, such groupishness in considering Christian theology is simply an error - but no longer an inevitable error; being instead the consequence of (for example) false metaphysics, wishful thinking, despair, dreadful fear - or a simple paucity of alternative ideas.
Therefore; we should understand the evolution of consciousness as the averaged outcome of our innate (inborn) spiritual-nature; with a multitude of individual human choices; concerning the outcomes of individually-tailored ("bespoke") interactions between each individual person with God and the Holy Ghost.