Meaning in human existence?

Our civilisation is only about 8,000 years old; so I have read. It was reported to have commenced after the end of the alleged Ice Age about 12,000 years ago. However, it is now claimed by some that there was no ice age involved; that it was a series of cosmic catastrophes culminating about 13,000 years ago that led to the present civilisation replacing previous human societies.. (Refer Cataclysm: compelling evidence of a cosmic catastrophe in 9,500 BC by D.S. Allan and J.B. Delair).
The theory about an ice age ending about 12,000 years ago is apparently only an unsupported theory, contradicted by evidence indicating an alternative approach. The Ice Age theory seems to be associated with the theory of uniformitarianism. This theory asserts that geological and related changes are always very gradual. Contrarily, since the 1950s, catastrophism has challenged this approach.
There is apparently substantial evidence supporting catastrophism, occurring in tandem with gradual change at most times. This may be similar to suddenly experiencing a nightmare, when normally one has the usual run of dreams. An incomplete theory comparable to uniformitarianism theory might be that of evolution, since there is apparently no evidence of inter-species evolution. Indeed, some scientific theories seem to me to be more like beliefs (but the best explanation available).
Mankind is said to have progressed from a stone age, through a series of metal ages, to an atomic-fission, man-destroys-man in quite colossal numbers, age (even as the global population has grown to such unsustainable levels).
Yet, there are hints of earlier advanced societies which had engaged in what reads as a nuclear war; the descriptions are apparently congruent with the damage seen in relatively recent times. Refer the clairvoyant Edgar Cayce’s ‘chanelling’ of historical scenes involving the land referred to as Atlantis in the Atlantic; as well as scholarly writings about a vast drowned continent referred to as Lemuria in the Pacific; and the alleged consequential dispersal of LemurIans to (mainly) the west coasts of North and South America. The similarity of huge stone structures, and celebratory rituals in Italy (of all places), Egypt, and sundry other places is said to reflect this dispersal.
Were there earlier civilisations? There are strong claims which do not involve spacemen. If so, and if they were destroyed by geological and extraterrestrial forces, has Nature not listened to our Creator? Or, has the Creator allowed Nature to teach us a lesson from time to time for not looking after our fragile home and (thereby) ourselves?