It has been noticed for more than a century that there is a broad correlation between ontogeny and phylogeny. Ontogeny is the development of an organism through its lifespan, while phylogeny refers to the sequence of forms leading from earlier to later members of the same presumed evolutionary lineage.
In terms of the evolutionary-development of conscience something analogous (and perhaps homologous - i.e. from the same causes) is seen in the change of consciousness during a human lifespan, and throughout human history.
In other words, the sequential development of consciousness from early through late childhood, into adolescence and adulthood; is similar to the sequence of human cultural conscience from the hunter-gatherer nomadic (analogous to early childhood); agrarian/ classical-medieval (older childhood); modern (adolescence) -- and the human society of 'adulthood' lies in the future (if enough people choose that path) and corresponds to whatever emerges from the first glimpses of what I have termed Primary Thinking, heart-thinking, or the state of Final Participation.
Why should this be? Why should our lifespan development correspond to the characteristic evolution of consciousness throughout history?
The explanation given by Rudolf Steiner and Owen Barfield is a version of reincarnation: that each modern individual has been incarnated multiple times in historical societies through history; so that the eternal 'self' (which persist between incarnations) undergoes cumulative linear transformation as a result of experience and learning.
In other words, modern people are more mature and developed than in the past, as a consequence of having incarnated many times before, in many types of society.
But I regard reincarnation as having been (whether wholly or mostly) ended by the work of Jesus Christ; such that since the time of Christ's death, Men have (pretty much) ceased to reincarnate; but instead make a choice between accepting or rejecting resurrected eternal life in Heaven.
(I think that there may be exceptions when some of those who reject Heaven may be allowed further reincarnation; when the souls desire and may benefit from this in terms of coming later to embrace resurrection due to further experience.)
Therefore I find myself advocating much the same scheme of evolutionary-development of consciousness - but without reincarnation as the explanation. What then is my explanation for (on average) 'more mature' souls being reincarnated in modern than in hunter-gatherer times?
(Note: 'More mature' does not correspond to 'better' in terms of more-Good or more likely to attain salvation. It just means more-mature. Plenty of adults are worse people than most children; many people get worse as they grow-up; and probably more modern children would choose salvation than modern adults. Nonetheless adults are indeed, on-average, more mature in consciousness than children.)
My answer to this relationship between ontogeny and phylogeny is to focus on the experiences we accumulate in pre-mortal life.
Following Mormon theology, I believe that we all had an (eternal) pre-mortal existence as immaterial spirits. In other words; before we incarnated into mortal bodies we were immortal spirits; and resurrected-incarnated immortality must be preceded by phases of spirit immortality and incarnated mortality.
The immortal pre-mortal spirits are each unique in terms of their original disposition and the differences due to different experience as spirits.
I don't think all pre-mortal spirits do the same thing (i.e. they have different 'jobs' or functions); but some at least are 'angels' - messengers and workers for the will of God.
(Other 'angels' are resurrected Men - so there are two types of angel: pre-mortal spirit, and post-mortal incarnate.)
Some of these spirit angels are apparently closely concerned with life on earth: some are what is termed 'guardian angels', that work very closely with incarnated mortal humans.
As the name implies, pre-mortal spirit angels do not have as much agency (or free will) as us mortal incarnates - they function more as intermediaries between God and mortal Men, conduits of God's will - they are, nonetheless, individuals, each an early step in Man's potential development.
(Potential development, because some pre-mortal spirits may choose to remain at that stage indefinitely. Mortal incarnation is optional, chosen.)
For instance, pre-mortal angels may be a link Men to God's presence, God's will, and a spiritual between Men. They may also perform miracles, under direction of God. They are agents in making early Man more naturally and spontaneously spiritual than modern Man.
In other words, an abundance of pre-mortal angels working closely with incarnate mortal Men may help account for the characteristics of Original Participation. Furthermore, these angels are building-up experience through living (spiritually) in close association with many of the various earlier forms of human society.
Later in history, after the time of Jesus Christ; at various points some of these angels are incarnated as mortal Men; and bring into mortal life the same maturity they have developed as pre-mortal angels.
Therefore, the evolution of consciousness through history is due to the greater maturity of more experienced incarnated souls; due to their having themselves lived-through much of previous human history - not incarnated, but in the form of spirits.
Part of this maturity is the 'spiritual adolescence' that rejects the spiritual influence of pre-mortal angels; rather as teenagers reject influence-by and association-with children.
One consequence of this scheme is that many of the pre-mortal spirit-angels live more like learners than helpers.
Thus 'guardian angels' may actually be more concerned with their own learning than with providing irreplaceable 'services'.
(Interestingly, this corresponds with the view of 'learner angels in some popular depictions - for what that is worth).
The above implies that some of us who are currently incarnated have probably been around and closely involved with human society and individuals at several or many times and places in human history - perhaps as pre-Christ reincarnates, and/or as post-Christ spirit-angels.
Why, then, do most people not remember something of this?
Well, some people do! And others have an implicit memory - like the memory of a dream (because spirit life has dream like qualities); but a dream than affects waking life.
Or even more like the implicit memories of very early childhood - mostly unrecalled, but affecting us in many ways.
If that is something like the way that these things work; then maybe many of us do have some kind of memories of this sort - perhaps evident in some of our innate aptitudes and preferences - as well as our varying degrees of innate, accumulated spiritual maturity