Paper 61 Overview: The Mammalian Era on Urantia

The mammalian era encompasses approximately fifty million years of Urantia's evolutionary history, beginning with the emergence of placental mammals and concluding with the retreat of the final continental ice sheets. This Cenozoic age witnessed dramatic geological transformations as continents shifted, land bridges formed and dissolved, and climate patterns evolved. Throughout this dynamic period, mammals progressively dominated the planetary ecosystem, developing from primitive forms into thousands of specialized species that exploited terrestrial, aquatic, and arboreal environments. The evolutionary advantages of mammals (particularly their parental care, neurological complexity, and adaptability) allowed them to supplant the formerly dominant reptilian species and establish new ecological paradigms.

The latter portion of the mammalian era was characterized by the episodic advance and retreat of massive glaciers that dramatically reshaped the northern landscapes. Six distinct glacial periods spanning two million years created the geomorphological features that would later influence human civilization, including the Great Lakes system of North America. Most significantly, toward the conclusion of this era, about one million years ago, the biologic precursors of humankind emerged in the form of dawn mammals, followed by mid-mammals and Primates, culminating in the appearance of the first true human beings. This evolutionary progression established the foundation for human civilization and marked Urantia's transition from a purely animal world to one harboring beings with the potential for spiritual consciousness and universe recognition.

The era of mammals extends from the times of the origin of placental mammals to the end of the ice age, covering a little less than fifty million years. During this Cenozoic age the world's landscape presented an attractive appearance—rolling hills, broad valleys, wide rivers, and great forests. Twice during this sector of time, the Panama isthmus went up and down; three times, the Bering Strait land bridge did the same. The animal types were both many and varied. The trees swarmed with birds, and the whole world was an animal paradise, notwithstanding the incessant struggle of the evolving animal species for supremacy.

The accumulated deposits of the five periods of this fifty-million-year era contain the fossil records of the successive mammalian dynasties and lead right up through the times of the actual appearance of man himself.

Fifty million years ago, earth's landmasses predominantly existed above sea level or with minimal submersion, though a continuous process of terrestrial uplift competed with simultaneous erosion that washed landforms down to lower elevations and toward the expanding seas. This dynamic geological period was characterized by formations and deposits of both marine and terrestrial origin, reflecting the complex interplay between land and sea environments. In North America, a revolutionary biological development occurred with the sudden appearance of placental mammals, representing an evolutionary advancement of unprecedented significance up to that historical moment. These pioneering placental species emerged directly and suddenly from persistent reptilian ancestors that had survived the widespread dinosaur extinction, with the progenitor of placental mammals being a small, highly active, carnivorous, springing type of dinosaur that initiated a new chapter in terrestrial vertebrate evolution.

The ascendancy of mammals stemmed from several evolutionary advantages that collectively conferred superior survival capability relative to other animal forms. Mammals demonstrated the ability to produce relatively mature and well-developed offspring, nurture and protect their young with affectionate regard, employ superior brain power for self-perpetuation, utilize increased agility to escape predation, and apply enhanced intelligence to environmental adaptation. As continental landmasses shifted, with widespread elevation of continental backbones and general coastal submergence approximately 45 million years ago, mammalian diversification accelerated dramatically. Small reptilian egg-laying mammals flourished alongside ancestral kangaroos, primitive horses, fleet-footed rhinoceroses, tapirs with proboscises, early pigs, squirrels, lemurs, opossums, and numerous monkey-like creatures. These species remained predominantly small and primitive, specially adapted for forest-dwelling in mountainous regions, while simultaneously developing distinctive mammalian characteristics including multiple mammary glands, body hair, sequential tooth development, and proportionally larger brains that foreshadowed later evolutionary advances.

The latter phase of this period, approximately 40 million years ago, witnessed significant geological transformations as Northern Hemisphere land areas underwent elevation, accompanied by extensive terrestrial deposits and various geological activities including lava flows, crustal warping, lake formation, and intensified erosion. Substantial portions of Europe submerged temporarily, later reemerging as a landscape dotted with lakes and bays, while the Arctic Ocean connected with an expanded Mediterranean Sea through the Ural depression. North America established continental connections with Asia via the Bering Strait land bridge and with Europe through Greenland and Iceland, creating a nearly complete land circuit in northern latitudes interrupted only by the Ural Straits. This geological configuration facilitated a period of extensive foraminiferal limestone deposition across European waters—strata that would eventually be elevated to heights of 10,000 feet in the Alps, 16,000 feet in the Himalayas, and 20,000 feet in Tibet. Throughout this Eocene period, mammalian evolution progressed steadily as North America maintained connections with nearly every continent except Australia, allowing primitive mammalian fauna to gradually populate the expanding global ecosystems.

The evolutionary momentum established in the preceding epoch accelerated during this period, characterized by further and rapid development of placental mammals, with progressively advanced forms of mammalian life emerging through natural selection and adaptive radiation. Although the earliest placental species descended from carnivorous progenitors, herbivorous branches quickly differentiated to exploit abundant plant resources, followed shortly thereafter by the appearance of omnivorous mammalian families that could utilize diverse food sources. The angiosperms, having established dominance in previous geological periods, provided the principal nutritional foundation for these rapidly diversifying mammals, as modern land flora, including the majority of contemporary plant and tree species, had already become well-established across terrestrial environments.

Approximately 35 million years ago marked a pivotal transition toward placental-mammalian dominance across global ecosystems, coinciding with extensive southern land bridge formation that reconnected the massive Antarctic continent with South America, South Africa, and Australia. Despite the concentration of landmasses at higher latitudes, the world climate remained relatively moderate due to the significant expansion of tropical seas and insufficient land elevation to generate glaciation. This period witnessed substantial lava flows in Greenland and Iceland, interspersed with coal deposits, while marine environments underwent profound transformations alongside the flourishing of foraminiferal species. The terrestrial realm experienced unprecedented mammalian renovation and expansion as over one hundred species of earlier and more primitive mammals became extinct when evolutionary pressures favored neurological development and physical agility rather than protective armoring and size. With the decline of dinosaur lineages, mammals assumed ecological dominance, rapidly eliminating remnant reptilian competitors while diversifying into specialized forms. Among these emerging mammalian groups was a unique, now-extinct carnivorous creature, something of a cross between a cat and a seal, that displayed amphibious capabilities and remarkable intelligence, giving rise to various mammalian lineages including canines, rodents, and other recognizable groups that persist with minimal modification to the present day.

Thirty million years ago, modern mammalian types began to appear as evolution drove specialization, particularly the divergence between mountainous, clawed flesh-eaters and plains-dwelling, hoofed grazing species. These grazers descended from an undifferentiated, five-toed ancestor with forty-four teeth that became extinct before the period's conclusion, though evolutionary toe reduction had not progressed beyond the three-toed stage during this timeframe. The horse, which would become a quintessential example of evolutionary progression, inhabited both North America and Europe, though its development remained incomplete until the subsequent ice age. Other notable developments included the emergence of rhinoceroses, a small hoglike creature ancestral to modern swine varieties, and early camels and llamas in North America that later migrated to South America and Europe respectively, though both eventually disappeared from their North American origins. Perhaps most significantly for human evolution, the early ancestors of true lemurs first appeared in western North America during this period, establishing the lineage from which genuine lemurs subsequently evolved. The Oligocene period, spanning approximately ten million years, concluded with plant and animal life largely evolved to forms recognizable today, with subsequent evolutionary developments primarily characterized by specialization rather than fundamental innovation of biological types.

Ongoing geological processes continued to transform global ecosystems as land elevation and sea segregation progressively altered weather patterns, initiating gradual planetary cooling though still maintaining relatively mild climatic conditions. The botanical evidence of this transition is preserved in the fossil record, which documents sequoias and magnolias growing in Greenland while subtropical plant species began migrating southward to more hospitable latitudes. By the conclusion of this period, warm-climate vegetation had largely disappeared from northern territories, replaced by more resilient plant varieties and the emerging deciduous forests that could withstand seasonal temperature variations. Concurrently, grasslands expanded significantly in diversity and distribution, triggering adaptive responses in numerous mammalian species whose dentition gradually transformed to accommodate grazing dietary patterns as evolutionary pressures selected for specialized herbivorous adaptations.

Twenty-five million years ago, slight land submergence interrupted the preceding long epoch of terrestrial elevation, though mountainous regions (particularly the Rocky Mountains) maintained their elevated status, continuing to contribute erosion materials to eastern lowlands. The Sierra Nevada range experienced significant re-elevation, initiating an ongoing uplift process that continues to present times, while California witnessed the formation of a dramatic four-mile vertical fault that dates precisely from this geological moment. The subsequent period, approximately 20 million years ago, truly represented the golden age of mammals, with the Bering Strait land bridge facilitating extensive migrations that introduced four-tusked mastodons, short-legged rhinoceroses, and numerous feline species into North America from Asian territories. The continent soon teemed with ruminants—deer, oxen, camels, bison, and several rhinoceros species—while giant pigs exceeding six feet in height disappeared through extinction events. Perhaps most notably, massive elephantine species with proportionally large brains flourished during this and subsequent periods, temporarily establishing neurological dominance across the planet with the exception of isolated Australia. These elephants represent a remarkable case study in evolutionary intelligence: no animal of comparable size could have survived without possessing both substantial brain volume and superior cognitive quality, approaching the horse in adaptive intelligence and surpassed only by humanity itself. Despite this evolutionary advantage, of the fifty elephant species existing at the period's commencement, only two ultimately survived to modern times.

The middle phase of this epoch, approximately 15 million years ago, witnessed continued mountain building throughout Eurasia, accompanied by localized volcanic activity, though at significantly reduced intensity compared to Western Hemisphere events. Dramatic reconfiguration of Mediterranean geography occurred as the Strait of Gibraltar closed, connecting Spain with Africa via the ancient land bridge, while the Mediterranean itself maintained an Atlantic connection through a narrow channel extending across France, with mountain peaks and highlands appearing as islands above this ancient sea. Later geological shifts connected the Mediterranean with the Indian Ocean before subsequent Suez region elevation temporarily transformed the Mediterranean into an isolated inland salt sea. Simultaneously, the Iceland land bridge submerged, allowing arctic waters to mix with Atlantic currents, cooling the North American Atlantic coastline while Pacific coastal regions remained comparatively warmer than present conditions. These shifting climate and geographical patterns influenced ongoing mammalian evolution, with enormous horse herds joining camels across the western plains in what genuinely constituted both the age of horses and elephants. The horse brain, second only to elephants in cognitive development, nevertheless remained evolutionarily disadvantaged by its deeply instinctual flight response to threatening stimuli, lacking the emotional control characteristic of elephantine species, while elephants themselves faced evolutionary constraints through their massive size and limited agility. During this period, Central Asia became the evolutionary cradle for true monkeys and gorillas, though these emerging primates, while sharing a common extinct ancestor, played no direct role in the evolutionary lineage that would eventually produce human beings.

This geological epoch is distinguished by extensive preglacial land elevation across North America, Europe, and Asia, profoundly transforming topographical features throughout these continental landmasses. The geomorphological alterations included mountain range formation, watercourse redirection, and isolated volcanic eruptions distributed globally, creating a substantially reorganized terrestrial landscape. Approximately 10 million years ago marked the beginning of an age characterized by widespread localized land deposits accumulating on continental lowlands, though most of these sedimentary formations were later eroded away by subsequent geological processes. Europe remained significantly submerged, including portions of England, Belgium, and France, while the Mediterranean Sea covered substantial areas of northern Africa. North American deposition concentrated around mountain bases, in lake beds, and throughout extensive land basins, averaging approximately 200 feet in thickness with variegated coloration but relatively sparse fossil content. Two massive freshwater lakes dominated western North America, while the Sierra Nevada range underwent elevation, and the nascent volcanoes Shasta, Hood, and Rainier began their mountain-building processes, though North America's gradual shift toward the Atlantic depression awaited the subsequent ice age.

For a brief geological interval, nearly all global landmasses reconnected with the singular exception of Australia, facilitating the final comprehensive worldwide animal migration. North America established connections with both South America and Asia, enabling unrestricted interchange of fauna as Asian sloths, armadillos, antelopes, and bears populated North American territories, while North American camels migrated to Asian environments including China. Rhinoceros species achieved virtually universal distribution except in Australia and South America, though they ultimately became extinct throughout the Western Hemisphere by the period's conclusion. Felidae (cat family) species achieved ecological dominance of terrestrial animal life during this time, while marine evolutionary development remained relatively static. Many equine species retained their three-toed configuration, though modern horse types were emerging in parallel. Llamas and giraffe-like camels coexisted with horses across expansive grazing plains, while the modern giraffe appeared in Africa exhibiting the same elongated neck characteristic of contemporary specimens. South American continental environments fostered the evolution of sloths, armadillos, anteaters, and primitive monkey species distinctive to that region. Before continental isolation through subsidence of land bridges, massive mastodons migrated throughout global territories with the singular exception of Australia, which remained biologically isolated from these megafaunal exchanges.

The culmination of this period, approximately 5 million years ago, witnessed the final evolution of the horse to its modern form, spreading globally from its North American evolutionary center, though ironically becoming extinct in its continental homeland long before human habitation by indigenous peoples. Progressively cooling climate conditions forced southward migration of land plants, while increasing northern cold initially restricted animal migrations across northern isthmuses before the eventual subsidence of North American land bridges eliminated these migration routes entirely. The subsequent submergence of the land connection between Africa and South America completed the isolation of the Western Hemisphere into its current geographical configuration, initiating distinct evolutionary trajectories for Eastern and Western Hemisphere life forms. This extended geological period, spanning nearly 10 million years, concluded without evidence of ancestral human beings, and corresponds to what contemporary paleontologists designate as the Pliocene epoch.

The transition to glacial conditions was precipitated by dramatic geological uplift across northeastern North America and northern Europe, with certain North American regions experiencing elevation increases exceeding 30,000 feet. These northern territories had previously enjoyed mild climates with open arctic waters readily contributing to evaporation cycles, remaining ice-free until the near-conclusion of the subsequent glacial period. The elevated landmasses, combined with fundamental shifts in oceanic currents and seasonal wind patterns, generated consistent precipitation as moisture-laden atmospheric systems moved across the northern highlands. Snow accumulation initiated on these elevated, cooler regions and continued unabated until reaching astounding depths of 20,000 feet. The areas of greatest snow accumulation, combined with their altitude, established the central points from which subsequent glacial pressure flows would originate and expand. This cyclic pattern of excessive precipitation covering northern highlands with massive snow deposits, which subsequently metamorphosed into solid but mobile ice sheets, determined both the intensity and duration of the ensuing ice age.

The distribution of ice sheets during this period was predominantly concentrated in the Northern Hemisphere, with approximately half of all glacial ice located in North America, one-fourth in Eurasia, and the remaining quarter distributed elsewhere, primarily across Antarctica. Africa experienced minimal glacial effects, while Australia, somewhat surprisingly, was almost entirely covered by the antarctic ice blanket. Northern global regions experienced six distinct glacial invasions, though dozens of advances and retreats occurred within the larger context of each individual ice sheet's overall activity. North American ice accumulated initially in two, and later three, pressure centers, with Greenland completely covered and Iceland entirely buried beneath flowing ice. European glaciation periodically encompassed the British Isles with the exception of southern England's coastline, and extended across western Europe as far south as France. The initial North American glacier began its southward advance approximately 2 million years ago, marking the commencement of the ice age proper, and required nearly one million years to complete its cycle of advance and subsequent retreat toward northern pressure centers. This central ice sheet extended southward to Kansas, though the eastern and western ice centers maintained more limited expansion during this initial glaciation.

The first major glacial retreat began approximately 1.5 million years ago, concurrent with enormous snow accumulation across Greenland and northeastern North America that soon initiated an eastern ice mass flow southward, constituting the second glacial invasion. These initial glacial advances remained relatively limited across Eurasian territories. Early ice age North America supported diverse megafauna including mastodons, woolly mammoths, horses, camels, deer, musk oxen, bison, ground sloths, giant beavers, saber-toothed tigers, elephant-sized sloths, and numerous feline and canine species. However, progressively intensifying cold conditions rapidly diminished these populations, and by the glacial period's conclusion, most species had become extinct throughout North America. Regions beyond the immediate influence of ice sheets experienced minimal climate and ecosystem disruption, with interglacial periods featuring conditions comparable to or slightly warmer than contemporary climate. The glacial phenomena, while geographically expansive, remained fundamentally localized in their direct environmental impact, though coastal climates fluctuated dramatically between glacial inactivity and periods when enormous icebergs calved from continental ice sheets into adjacent oceans.

The evolutionary appearance of primitive human beings represents the most significant development during this glacial period, fundamentally transforming Urantia's biological trajectory. In a region west of the Indian subcontinent, on territories currently submerged beneath ocean waters, the dawn mammals emerged among descendants of Asian migrants from older North American lemur lineages. These diminutive creatures primarily adopted bipedal locomotion and possessed disproportionately large brains relative to their physical size and compared with contemporary animal species. An extraordinary evolutionary sequence unfolded across approximately seventy generations of this specialized mammalian order, culminating in the differentiation of mid-mammals—creatures nearly twice the size and height of their ancestors with correspondingly enhanced cognitive capabilities. The evolutionary momentum continued with the subsequent appearance of the Primates, representing the third critical mutation in this progressive sequence. Concurrent with these advancements, a retrograde development within mid-mammal populations established the ancestral simian lineage, creating an evolutionary divergence that would prove significant for planetary life. From this bifurcation point forward, the human branch progressed through continuous evolutionary advancement, while simian tribes remained relatively static or experienced evolutionary regression.

Approximately one million years ago, Urantia achieved formal registration as an inhabited world following a mutation within the progressive Primate lineage that produced two primitive human beings—the authentic progenitors of humanity. This momentous event coincided with the initiation of the third glacial advance, placing human evolutionary origins within an environmentally challenging context that likely contributed to the development of human resilience and adaptability. The only contemporary descendants of these Urantia aborigines, the Eskimos, continue to demonstrate preference for frigid northern climates, perhaps reflecting this evolutionary heritage. Human presence remained absent from the Western Hemisphere until near the conclusion of the ice age, though during interglacial periods, early humans migrated westward circumnavigating the Mediterranean basin before populating the European continent. Archaeological evidence from western European caves reveals human remains intermixed with both tropical and arctic animal fossils, providing physical testimony that humans inhabited these regions throughout successive phases of glacial advancement and retreat, adapting to dramatically fluctuating climatic conditions through developing cultural and technological innovations that compensated for their biological limitations.

While the northern latitudes experienced the dominant influence of glacial activity, numerous other geological processes continued throughout this period, though ice movements overshadowed alternative terrestrial phenomena across affected regions. No other natural process has left such distinctive evidence in topographical formations, including characteristic boulders, surface cleavages, pothole formations, lakes, displaced stone, and rock flour deposits that appear exclusively in connection with glacial activity. Ice sheets also generated gentle surface undulations known as drumlins, displaced existing river systems, and comprehensively transformed landscape features across vast geographical areas. The retreating glaciers left behind telltale drift formations—ground, lateral, and terminal moraines—that provide clear geological markers of their historical presence and extent. The fourth North American glaciation, representing a unified advance of central and eastern ice fields, reached southward to southern Illinois, displacing the Mississippi River fifty miles westward, while extending eastward to the Ohio River and central Pennsylvania.

Seven hundred fifty thousand years ago, the fourth glacial sheet extended across these expansive territories, while the Siberian ice sheet made its furthest southern incursion in Asia, and European ice progression halted just short of the Alpine mountain barriers. A subsequent planetary development of profound significance occurred approximately 500,000 years ago during the fifth glacial advance, when the six colored races mutated from aboriginal human stock within a single generation, coinciding precisely with the arrival of the Planetary Prince. The sixth and final glaciation commenced 250,000 years ago despite initial subsidence of northern highlands, paradoxically representing the period of maximum snow deposition across northern ice fields. This final advance witnessed the coalescence of three major ice sheets into a single massive ice formation, with western mountain ranges participating in this glacial activity as ice moved southward more than fifteen hundred miles from its pressure centers, subjecting North America to its lowest historical temperatures. The Lucifer rebellion erupted 200,000 years ago during this final glacial advance, introducing additional complexity to planetary development as ice sheets reached maximum southern extension 150,000 years later, with western ice crossing the Canadian border, central ice reaching into Kansas, Missouri, and Illinois, and eastern ice covering most of Pennsylvania and Ohio.

The retreating glaciers carved multiple extensions or lobes that created contemporary lake formations, both large and small, across previously ice-covered territories. The North American Great Lakes system emerged during this retreat phase, initially draining into the Mississippi valley before shifting eastward into the Hudson valley, and finally establishing the northern drainage route through the St. Lawrence, which began functioning approximately 37,000 years ago. As the final glacier retreated, vast polar ice sheets formed with the accumulation center shifting considerably northward, establishing conditions that make future glacial episodes highly improbable regardless of land elevation changes or ocean current modifications. The last glacial advance required 100,000 years to reach its maximum extent and an equivalent timespan to complete its northern retreat, with temperate regions enjoying ice-free conditions for approximately 50,000 years. The rigorous glacial environment eliminated numerous species while forcing substantial adaptation in others, particularly those species engaged in repeated north-south migrations following glacial advance and retreat cycles. The concluding period of glaciation formally terminated approximately 35,000 years ago except in polar regions, roughly corresponding with the arrival of a Material Son and Daughter and the commencement of the Adamic dispensation, marking the transition to the Holocene or post-glacial period that has encompassed the entirety of recorded human civilization.