(49:1.6) The early stages of life evolution are not altogether in conformity with your present-day views. Mortal man is not an evolutionary accident. There is a precise system, a universal law, which determines the unfolding of the planetary life plan on the spheres of space. Time and the production of large numbers of a species are not the controlling influences. Mice reproduce much more rapidly than elephants, yet elephants evolve more rapidly than mice.
(49:1.7) The process of planetary evolution is orderly and controlled. The development of higher organisms from lower groupings of life is not accidental. Sometimes evolutionary progress is temporarily delayed by the destruction of certain favorable lines of life plasm carried in a selected species. It often requires ages upon ages to recoup the damage occasioned by the loss of a single superior strain of human heredity. These selected and superior strains of living protoplasm should be jealously and intelligently guarded when once they make their appearance. And on most of the inhabited worlds these superior potentials of life are valued much more highly than on Urantia.
(61:7.13) The rigorous glacial period destroyed many species and radically changed numerous others. Many were sorely sifted by the to-and-fro migration which was made necessary by the advancing and retreating ice. Those animals which followed the glaciers back and forth over the land were the bear, bison, reindeer, musk ox, mammoth, and mastodon.
(58:6.3) From era to era radically new species of animal life arise. They do not evolve as the result of the gradual accumulation of small variations; they appear as full-fledged and new orders of life, and they appear suddenly.
(59:1.4) Suddenly and without gradation ancestry the first multicellular animals make their appearance. The trilobites have evolved, and for ages they dominate the seas. From the standpoint of marine life this is the trilobite age.
(59:3.5) The trilobites rapidly declined, and the center of the stage was occupied by the larger mollusks, or cephalopods. These animals grew to be fifteen feet long and one foot in diameter and became masters of the seas. This species of animal appeared suddenly and assumed dominance of sea life.
(59:3.11) Toward the close of the final Silurian submergence there is a great increase in the echinoderms—the stone lilies—as is evidenced by the crinoid limestone deposits. The trilobites have nearly disappeared, and the mollusks continue monarchs of the seas; coral-reef formation increases greatly. During this age, in the more favorable locations the primitive water scorpions first evolve. Soon thereafter, and suddenly, the true scorpions—actual air breathers—make their appearance.
(59:4.13) The earth was being rapidly overrun by the new orders of land vegetation. Heretofore few plants grew on land except about the water’s edge. Now, and suddenly, the prolific fern family appeared and quickly spread over the face of the rapidly rising land in all parts of the world. Tree types, two feet thick and forty feet high, soon developed; later on, leaves evolved, but these early varieties had only rudimentary foliage. There were many smaller plants, but their fossils are not found since they were usually destroyed by the still earlier appearing bacteria.
(59:5.5) When the seas were at their height, a new evolutionary development suddenly occurred. Abruptly, the first of the land animals appeared. There were numerous species of these animals that were able to live on land or in water. These air-breathing amphibians developed from the arthropods, whose swim bladders had evolved into lungs.
(60:1.9) 140,000,000 years ago, suddenly and with only the hint of the two prereptilian ancestors that developed in Africa during the preceding epoch, the reptiles appeared in full-fledged form. They developed rapidly, soon yielding crocodiles, scaled reptiles, and eventually both sea serpents and flying reptiles. Their transition ancestors speedily disappeared.
(60:3.19) Great plant-life evolution was taking place. Among the land plants the angiosperms predominated, and many present-day trees first appeared, including beech, birch, oak, walnut, sycamore, maple, and modern palms. Fruits, grasses, and cereals were abundant, and these seed-bearing grasses and trees were to the plant world what the ancestors of man were to the animal world—they were second in evolutionary importance only to the appearance of man himself. Suddenly and without previous gradation, the great family of flowering plants mutated. And this new flora soon overspread the entire world.
(61:1.2) Early in this period and in North America the placental type of mammals suddenly appeared, and they constituted the most important evolutionary development up to this time. Previous orders of nonplacental mammals had existed, but this new type sprang directly and suddenly from the pre-existent reptilian ancestor whose descendants had persisted on down through the times of dinosaur decline. The father of the placental mammals was a small, highly active, carnivorous, springing type of dinosaur.
(61:2.8) 30,000,000 years ago the modern types of mammals began to make their appearance. Formerly the mammals had lived for the greater part in the hills, being of the mountainous types; suddenly there began the evolution of the plains or hoofed type, the grazing species, as differentiated from the clawed flesh eaters. These grazers sprang from an undifferentiated ancestor having five toes and forty-four teeth, which perished before the end of the age. Toe evolution did not progress beyond the three-toed stage throughout this period.
(61:6.1) The great event of this glacial period was the evolution of primitive man. Slightly to the west of India, on land now under water and among the offspring of Asiatic migrants of the older North American lemur types, the dawn mammals suddenly appeared. These small animals walked mostly on their hind legs, and they possessed large brains in proportion to their size and in comparison with the brains of other animals. In the seventieth generation of this order of life a new and higher group of animals suddenly differentiated. These new mid-mammals—almost twice the size and height of their ancestors and possessing proportionately increased brain power—had only well established themselves when the Primates, the third vital mutation, suddenly appeared. (At this same time, a retrograde development within the mid-mammal stock gave origin to the simian ancestry; and from that day to this the human branch has gone forward by progressive evolution, while the simian tribes have remained stationary or have actually retrogressed.)
(62:2.1) A little more than one million years ago the Mesopotamian dawn mammals, the direct descendants of the North American lemur type of placental mammal, suddenly appeared. They were active little creatures, almost three feet tall; and while they did not habitually walk on their hind legs, they could easily stand erect. They were hairy and agile and chattered in monkeylike fashion, but unlike the simian tribes, they were flesh eaters. They had a primitive opposable thumb as well as a highly useful grasping big toe. From this point onward the prehuman species successively developed the opposable thumb while they progressively lost the grasping power of the great toe. The later ape tribes retained the grasping big toe but never developed the human type of thumb.
See 2017 article about the evolution of a new finch species on the Galapagos Islands.