The Great Story Timeline, Part 2

VIII. Cenozoic Era (Age of Mammals and Birds) begins.

(Use small green beads as spacers, with different hues of green for the first 6 of 7 epochs of the Cenozoic. Use pink and white beads for the final, Holocene, epoch.)

The Cenozoic has only two geological "periods" — the Tertiary and the Quaternary (or sometimes divided into the Paleogene and the Neogene) — but it is more helpful to speak of the geological "epochs" within these periods. The Tertiary entails the Paleocene, Eocene, Oligocene, Miocene, and Pliocene epochs. The Quaternary includes just the Pleistocene and the Holocene epochs. For our purposes, we treat the Paleocene through the Pleistocene as hues of green. Even though humans originated in the Pleistocene, we did not become a dominant force on Earth until the Holocene. We use various shades of pink and white beads for the Holocene, to mark significant periods within the human realm.

65-57 mya PALEOCENE

• The "GOLDEN AGE OF TURTLES" in North America, as turtles that could hibernate in the mud may have been the only large vertebrates in North America that made it through the Mexico impact event. This is also the birth of TURTLE ISLAND — a Native American name for North America. The inland sea that had flooded the middle of the continent, from the Arctic to the Gulf of Mexico, during the Mesozoic is now vanished, revealing a single continent. Note: Because North America is our home, we focus on North American events during the Cenozoic.
  
  
• 61 mya — MAMMALS embark on a stunningly fast evolution. Within just four million years (65—61 mya) amazing new forms evolve to fill the empty ecological roles left by the dinosaurs. Hoofed mammals achieve glorious diversity, though they are still no larger than dog-size.

57-34 mya EOCENE

• HORSE, CAMEL, AND DOG families arise in North America.
  
  
• ELEPHANT, RHINO, AND PRIMATE families arise in the Old World.
  
  
• A global GREENHOUSE allows massive interchange of even tropical life between continents across the Arctic. Montana and the Dakotas are home to tropical rainforest plants in the magnolia, citrus, fig, pawpaw, and cashew families, with early PRIMATES and squirrel-like MULTITUBERCULATES cavorting in the forest canopy. At 75º latitude in the Canadian Arctic (Ellesmere Island), subtropical plants and animals (alligators) thrive. Winters are dark that far north, but not cold; plants do shed their leaves for the dark time; reptiles, amphibians, and mammals go into dormancy.
  
  
• DIATRYMA, the "terror crane" of North America, is a gigantic, eight foot tall, flightless bird with a stout nine-inch beak, who stalks prey upright, as T. rex did.
  
  
• The first really big mammals evolve and rise up into the biggest land mammals of all time: the rhino-like uinthatheres and BRONTOTHERES of North America and the indricotheres of Asia (the largest of which weighed 20 tons and stood 18 feet tall at the shoulder).
  
  
• WHALE ancestors return to the sea.
  
  
• LATE EOCENE (mini) EXTINCTION. Many types of large mammals disappear, including all the uintatheres and brontotheres and indricotheres. Primates, once abundant and diverse in North America, disappear from this continent. Rodent-like multituberculates, which had originated in the Cretaceous, go globally extinct. Asteroid impacts are implicated, as two large, buried craters (each half the size of the Yucatan crater tied to the dinosaur extinction) were discovered in the 1990s beneath Chesapeake Bay in the eastern United States and in Russia. They are dated to about 35 mya.

  34-23 mya OLIGOCENE

• Paleontologists refer to this time as "The Big Chill." The sea ridge that connected Australia to Antarctica at a shallow depth disappears, giving birth to the deep Antarctic Circumpolar Current. A globally cooler climate and intense SEASONALITY develops.
  
  
• Deciduous trees thrive, including the deciduous conifer METASEQUOIA. Also known as "dawn redwood," metasequoias become as common in western North America as pines are today.
  
  
• Many of our familiar FRUIT TREE FAMILIES originate (or, at least, this is when their first fossils show up).
  
  
• The DAISY FAMILY comes into existence and rapidly evolves into the most species-rich of all plant families.
  
  
• SQUIRRELS originate in North America and co-evolve with NUT TREES.
  
  
• RAVENS fly into North America for the first time, having originated in Australia.
  
  
• TOADS enter North America for the first time, rafting across the sea from South America.
  
  
• The first MONKEYS arrive in South America and diversify, presumably after having rafted in from Africa.

  23—5 mya MIOCENE

• The ROCKY MOUNTAINS are uplifted for a second time, after having eroded nearly away.
  
  
• A catastrophic flow of COLUMBIAN FLOOD BASALT covers what is today eastern Washington in lava.
  
  
• The entire Miocene is the GOLDEN AGE OF MAMMALS, with an astounding diversity of mammalian species on land. Camels, still confined to North America, diversify into forms that resemble African gazelles and giraffes. Many kinds of peccaries fulfill the "pig" niche in North America. These are examples of "convergent evolution": Earth itself is calling forth the gazelle form, the giraffe form, the pig form, and will work on whatever lineage is available!
  
  
• At the water's edge, the bear family sends ancestors of SEALS back into the sea.
  
  
• The global climate warms, but it is still very dry, providing ideal conditions for modern GRASSES to flourish. Grasses cope well with drought and are superbly adapted to survive mammal grazing (because the growing cells of grasses are concealed at the base, not exposed at the tip). Some mammals co-evolve high-crowned teeth to withstand abrasion from silica granules embedded in grasses. Woody/grassy savannas spread throughout the world. (Grasses — wheat, barley, rice, maize, oats, millet — will later support the emergence of agriculture.) After 200 million years of stunning persistence, the whole taxonomic order of GINKGO (Ginkgoales) goes extinct in the western hemisphere, and nearly extinct in Asia. The dawn redwood (Metasequoia) goes extinct in North America too, hanging on in Japan until the Pleistocene. (In 1944, scientists will be thrilled to discover about 100 metasequoia trees still alive in Szechwan Province of China. As with ginkgo, humans will revive the lineage: both trees now can be found in parks and gardens throughout the world.)
  
  
• The first elephants — MASTODONS — arrive in North America from the Old World, along with BEAVERS, while VULTURES fly in from South America.
  
  
• The PRONGHORN family (Antilocapridae) originates in North America (only one species remains today: the American pronghorn).
  
  
• CHEETAHS originate in North America. This is the only cat genus (Acinonyx) to ever originate in the Western Hemisphere, although there were catlike forms of the nimravid lineage much earlier in the Cenozoic. (Meanwhile, isolated South America had marsupial "cats" that evolved the same body forms and teeth as our placental true cats and as the nimravids.) The cat form is thus another remarkable example of "convergent evolution" during the Cenozoic.
  
  
• Only a narrow sea now separates North from South America, which had long been isolated by a vast expanse of water. WHIPTAIL LIZARDS are carried to North America from South America (probably on floating logs). TORTOISES (distinct from turtles) float from North America to South America.
  
  
• 5 mya the Miocene ends in a severe drought. The Great Plains region shifts from a wooded savanna to a true steppe grassland. There are some EXTINCTIONS in North America — notably all North American members of the rhinoceros family.

5-2 mya PLIOCENE

• MAMMOTHS venture into North America from the Old World and proliferate.
  
  
• The DEER family immigrates into North America from Asia for the first time. Meanwhile, the DOG and CAMEL families, which arose long ago in North America, successfully send their first emissaries out to the rest of the globe via Asia.
  
  
• 5 mya hominids, chimpanzees, and BONOBOS (pygmy chimpanzees) diverge from a common ancestor in Africa. Recent studies have shown that 98.7% of human DNA is identical with the bonobos and chimpanzees — revealing them to be our closest genetic cousins.
  
  
• Pressed southward by advancing glacial ice, TULIP TREES (Liriodendron, Magnolia family) go extinct in Europe and western North America. A remnant population takes refuge in northern Florida and survives to repopulate eastern North America as the climate warms.
  
  
• The Colorado Plateau is rapidly uplifted, which produces the GRAND CANYON and the geological extravagances of Bryce and Zion parks.
  
  
• 3 mya the ISTHMUS OF PANAMA forms, joining the two continents for the first time since the Mesozoic. This is likely the origin of the Gulf Stream, which brings warm, moist air up from the tropics along the eastern shore of North America, then across to Europe. Formation of the isthmus also prompts "THE GREAT AMERICAN INTERCHANGE," an event that is a crisis for some lineages and an opportunity for others. Small ground sloths had swum across earlier, but now South America sends north its giant ground sloths, tanklike glyptodonts, porcupines, and armadillos (all of the taxonomic order Edentata, which originated in South America), plus marsupial opossums, and a ten-foot tall carnivorous bird: Titanis. In exchange, North America sends southward its foxes, deer, mice, skunks, rattlesnakes, rabbits, squirrels, tapirs, camels (llamas), cats, bears, weasels, snapping turtles, and small mastodons (gomphotheres) — none of which South America had ever before experienced. The influx of northern animals honed by ecological interactions in the vast northern hemisphere proves too much for many South American endemic species, which go extinct. "Native" South American animals alive today are thus mostly less than three million years native.
  
  
• 2.5 mya HUMAN BEINGS (Homo habilis — "handy human") use stone tools.

  2 mya to 13,000 years ago — PLEISTOCENE

• GLACIAL ICE advances and retreats at least 17 times, with four major waves in North America.
  
  
• 1.4 mya humans (Homo erectus) domesticate FIRE.
  
  
• CARIBOU originate about a million years ago, probably in North America.
  
  
• POLAR BEARS evolve from the Asian grizzly bear in just 200,000 years.
  
  
• BISON emigrate from Asia into the New World for the first time about 400,000 years ago, eventually producing endemic species native to North America.
  
  
• 50,000—500,000 years ago SYMBOLIC LANGUAGE emerges, marking the birth of beliefs and metaphors for comprehending the nature of Reality and our relationship to it in all its manifestations. This marks a radical shift. For 80-95% of human history we experienced life — we remembered, made choices, learned, pair-bonded, raised children, and were guided by instinct, experience, and non-verbal tradition, or "culture" — without any internal conversation going on in our heads. In other words, we lived and communicated as other animals do — intuitively and experientially, making full use of our senses — and were guided by the whole of Reality (within and outside us) just as all other creatures are. Mythically, while this can be considered HUMANITY'S FALL FROM THE GARDEN, it should also be recognized as AN ENORMOUS LEAP IN COMPLEXITY, and a hugely positive development at a number of levels. Symbolic language widens the range of possible feelings that can be experienced. It makes abstract thought achievable — hence, science and religion. It also allows us to communicate something of the past — storytelling — and to work with others in planning future actions. In all of these ways, symbolic language makes it possible for the Universe to come to know and experience itself in a new way, in and through the human.
  
  
• 50,000 years ago, humans enter AUSTRALIA via a land bridge from Southeast Asia, uncovered by a decline in sea level resulting from glacial ice piling up on land. They, and the dingo they bring with them, cause an "extinction of the massive" among Australia's biggest marsupials, reptiles, and flightless birds. Australia loses all but one of its sixteen genera of terrestrial vertebrates weighing 100 pounds or more. THE SIXTH MAJOR MASS EXTINCTION thus begins with this AUSTRALIAN EXTINCTION. 35,000 years ago, the most recent advance of glacial ice begins; it will peak at 18,000 years ago and begin to melt away 15,000 years ago.
  
  
• 30,000 years ago, humans create the first CAVE PAINTINGS.
  
  
• 23,000 years ago, peoples living in Europe sculpted (and later painted) figures of the DIVINE FEMININE.
  
  
• CREOSOTEBUSH arrives in North America from South America (probably in the feathers of a migrating bird). Because there are no North American insect predators evolved to keep it in control and because camels (who would eat it) will soon go extinct, creosotebush begins to take over the warm reaches of the desert west. Also, the spruce-parkland landscape type goes extinct, although the individual plant species do not.
  
  
• 13,000 years ago, humans enter the Americas. In just 300 years, the CLOVIS culture causes EXTINCTION OF THE MASSIVE IN NORTH AMERICA, owing to overkill. Mastodons, mammoths, ground sloths, glyptodonts, horses, camels, long-horned bison, giant tortoises, and those who preyed or scavenged upon them (sabertooth cats, short-faced bear, American lion, giant hyena, teratorn birds) all go extinct. North America loses 32 of its 47 genera of "megafauna" — those animals with adult weights of 100 pounds or more. Meanwhile, South America loses 47 of its 59 genera of megafauna. Mammals that had learned to cope with humans in Asia now successfully migrate into North America for the first time: elk, moose, plains bison, grizzly bear.

  TO VIEW the final of three files of the timeline (which brings us to the present), click here:

  Timeline 1 — Big Bang to 65,000,000 Years Ago

  Timeline 3 — 12,000 Years Ago to Present