The consciousness related feeling of being alive is shared by all living beings and every one of them responds to the external stimuli in a specific way on individual or community level. Experiments suggest that about forty percent of men recount their past births suggesting continuance of memory, feelings and emotions beyond the physical system after death. All this has happened as an outcome of a long process in evolution in the organic world, commencing nearly three and half billion years ago.

Our earth was born around four and half billion years ago as a ball of hot nebulous gases. It gradually cooled and then life commenced in near boiling waters around 3.5 billion years (Ga) in an atmosphere devoid of oxygen. History of earth has thus a duration of no life, followed by an era of very primitive invisible life giving way to an era of visible life of various sizes and shapes. These large segments of time have been divided into smaller units likes Eras and Periods to measure the prominent events in the earth's history. The span of visible life or Phanerozoic Eon, for example, commencing some 590 million years ago has three eras—Paleozoic, Mesozoic and Cenozoic—denoting old life, middle life and new life. Major extinctions in animal life mark the boundaries of these eras. Life has been continuously evolving through the geological times adding more and more consciousness among individuals.

In the primordial atmosphere, left behind after condensation of water, there was hardly any free oxygen. It was here, in the nearly boiling and an anoxic atmosphere that consciousness first manifest as  earthly life where the land, water and  atmosphere met. The life so formed comprised of  anaerobic thermophilic microbes or the bacteria that sustain themselves in oxygen free, hot waters. Such a life dates back 10 nearly 3.5 billion years.

The primary atmosphere of earth was constituted by nitrogen, carbon dioxide, water vapour and hydrogen sulfide. Oxygen was needy absent It was generated as a part of biological activity by gradually breaking down the carbon dioxide in the atmosphere. From anoxic bacteria in the primordial atmosphere arose oxygen breathing microbes with gradual addition of oxygen in the later atmosphere. This change started a few million years after the first life appeared on the earth. Considering the abundance of fossil stromatolites in the rock-strata, growing exclusively in the oxygen-rich environment has been established that oxygen had become a common component of earth's atmosphere around 2.3 Ga. as abundance of purely oxic life was established around two billion years ago.

Once the life had acquired oxygen breathing potential, its diversification followed in plants and animals both. However, once again an anaerobic respiration is seen in mammalian muscle cells under the conditions of oxygen deprivation. it is a second evolution towards specialised acquisition of the primal anoxic breathing active and has highest utilization among yogis who cut down oxygen intake in the system forcibly through eight steps to samadhi. It is in samadhi that a yogi experiences, feels and sees himself as a true consciousness being when he subjugates oxygen dependent human body and terminates the animal control system of the body. Secondary anoxophily is, therefore, the ultimate level of evolution in the organic world and yogi is as final product.

Eventhough microscopic and very small, around one twentieth to one hundredth of a millimeter, the life shows diverse activities at the the bacterial level. It is abundantly seen in the Vindhyan sediments of India dating back between 0.7 to 1.4 Ga. Vindhyan rocks contain abundant stromatolitic limestones as well as shales rich in micro-organic maker with diverse prokaryotes or non-nucleate forms and newly emergent unicellular eukaryotes or nucleus bearing organisms.
The early biosphere, as seen through the fossils of the Vindhyan shales around a billion year old, occupied all the niches of water with pretty diverse life which has taken almost all modes of existence seen in the living forms. There were active bottom dwellers and there were plate-like floaters besides those with specialised balloons. Forms were also with whipping flagellum very similar to human sperm swimming in the then waters. Organism with a distinct mouth, either micro-scavenger or predators, are also seen here.

The organic evolution, stagnant for long, under unicellular stage made its maiden experiment in the expansion of consciousness through colonization. Tuffs and bundles of linear thread like bodies are seen abundantly among the Vindhyan shales. Clustering of individuals ink a colony where, individuals shared same food habit and survival problems, ensured better prospects of  survival for  a species. Colonization  thus came to exist for ensuring comparatively better chances of longevity at a species level. This initial experiment of nature for the safety and survival of a species has generated an independent community consciousness unit for every bundle on the same pattern as community consciousness of a bee-hive. It acted on the same maxims :individual consciousness Unit or individual may be sacrificed, if it suites the community .

The living Nature realized, that colonisation at the prokaryote level does not create a sufficiently large system of consciousness on the individual level. An unicellular form could not reach very large size and perform complex functions. It embarked on a new course of consciousness accretion among individuals thereafter. It was the process of addition of cells to make bigger plants and animals. Once the process set in, around 0.8 billion years ago, it has continued till date. There are giant sequoya trees and magnificent whales, millions of times bigger than the earliest life. However, this physical giganticism has been found superfluous and abandoned in the most evolved beings holding consciousness—a yogi. Basically, it has happened due to highly organized brain in man, seen no where in any other form of life.