P664:2, 58:1.1 600,000,000 years ago the commission of Life Carriers sent out from Jerusem arrived on Urantia and began the study of physical conditions preparatory to launching life on world number 606 of the Satania system. This was to be our six hundred and sixth experience with the initiation of the Nebadon life patterns in Satania and our sixtieth opportunity to make changes and institute modifications in the basic and standard life designs of the local universe.
P664:3, 58:1.2 It should be made clear that Life Carriers cannot initiate life until a sphere is ripe for the inauguration of the evolutionary cycle. Neither can we provide for a more rapid life development than can be supported and accommodated by the physical progress of the planet.
P664:4, 58:1.3 The Satania Life Carriers had projected a sodium chloride pattern of life; therefore no steps could be taken toward planting it until the ocean waters had become sufficiently briny. The Urantia type of protoplasm can function only in a suitable salt solution. All ancestral life -- vegetable and animal -- evolved in a salt-solution habitat. And even the more highly organized land animals could not continue to live did not this same essential salt solution circulate throughout their bodies in the blood stream which freely bathes, literally submerses, every tiny living cell in this "briny deep."
P664:5, 58:1.4 Your primitive ancestors freely circulated about in the salty ocean; today, this same oceanlike salty solution freely circulates about in your bodies, bathing each individual cell with a chemical liquid in all essentials comparable to the salt water which stimulated the first protoplasmic reactions of the first living cells to function on the planet.
P664:6, 58:1.5 But as this era opens, Urantia is in every way evolving toward a state favorable for the support of the initial forms of marine life. Slowly but surely physical developments on earth and in adjacent space regions are preparing the stage for the later attempts to establish such life forms as we had decided would be best adapted to the unfolding physical environment -- both terrestrial and spatial.
P665:1, 58:1.6 Subsequently the Satania commission of Life Carriers returned to Jerusem, preferring to await the further breakup of the continental land mass, which would afford still more inland seas and sheltered bays, before actually beginning life implantation.
P665:2, 58:1.7 On a planet where life has a marine origin the ideal conditions for life implantation are provided by a large number of inland seas, by an extensive shore line of shallow waters and sheltered bays; and just such a distribution of the earth's waters was rapidly developing. These ancient inland seas were seldom over five or six hundred feet deep, and sunlight can penetrate ocean water for more than six hundred feet.
P665:3, 58:1.8 And it was from such seashores of the mild and equable climes of a later age that primitive plant life found its way onto the land. There the high degree of carbon in the atmosphere afforded the new land varieties of life opportunity for speedy and luxuriant growth. Though this atmosphere was then ideal for plant growth, it contained such a high degree of carbon dioxide that no animal, much less man, could have lived on the face of the earth.