This period includes the Miocene (23.03 to 5.332 Ma), and Pliocene, the second epoch of the Neogene, which extends from 5.332 million to 1.806 million years before present.
The Neogene traditionally ended at the end of the Pliocene epoch, just before the older definition of the beginning of the Quaternary Period; many time scales show this division. However, there is a movement amongst geologists (particularly Neogene Marine Geologists) to also include ongoing geological time (Quaternary) in the Neogene, while others (particularly Quaternary Terrestrial Geologists) insist the Quaternary to be a separate period of distinctly different record. The somewhat confusing terminology and disagreement amongst geologists on where to draw what hierarchical boundaries, is due to the comparatively fine divisibility of time units as time approaches the present, and due to geological preservation that causes the youngest sedimentary geological record to be preserved over a much larger area and reflecting many more environments, than the slightly older geological record. By dividing the Cenozoic era into three (arguably two) periods (Paleogene, Neogene, Quaternary) instead of 7 epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras.
The Neogene covers roughly 23 million years. During the Neogene mammals and birds evolved considerably. Most other forms were relatively unchanged. Some continental motion took place, the most significant event being the connection of North and South America in the late Pliocene. Climates cooled somewhat over the duration of the Neogene culminating in continental glaciations in the Quaternary sub-era (or period, in some time scales) that follows, and that saw the dawn of the genus Homo.
During the beginning of the Neogene, climates remained moderately warm, although the slow global cooling that eventually led to the Pleistocene glaciations continued. Mountain building took place in Western North America and Europe. Both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines. Well studied continental exposures occur in the American Great Plains and in Argentina. India continued to collide with Asia, creating more mountain ranges. The Tethys Seaway continued to shrink and then disappeared as Africa collided with Eurasia in the Turkish-Arabian region between 19 and 12 mya. Subsequent uplift of mountains in the western Mediterranean region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea (known as the Messinian salinity crisis) near the end of the Miocene.
Although a long-term cooling trend was well underway, there is evidence of a warm period during the Miocene when the global climate rivaled that of the Oligocene. The Miocene warming began 21 million years ago and continued until 14 million years ago, when global temperatures took a sharp drop - the Middle Miocene Climate Transition (MMCT). By 8 million years ago, temperatures dropped sharply once again, and the Antarctic ice sheet was already approaching its present-day size and thickness. Greenland may have begun to have large glaciers as early as 7 to 8 million years ago, although the climate for the most part remained warm enough to support forests there well into the Pliocene.
During the Miocene, grasslands underwent a major expansion as forests fell victim to a generally cooler and drier climate overall. Grasses also diversified greatly into different species and also caused a major increase in the biodiversity of large herbivores and grazers, including ruminants.
Both marine and continental fauna were fairly modern, although marine mammals were less numerous. Only in isolated South America and Australia did widely divergent fauna exist. Mammals were also modern, with recognizable wolves, raccoons, horses, beaver, deer, camels, and whales.
Recognizable crows, ducks, auks, grouses and owls appear in the Miocene. By the epoch's end, all or almost all modern families are believed to have been present; the few post-Miocene bird fossils which cannot be placed in the evolutionary tree with full confidence are simply too badly preserved instead of too equivocal in character. Marine birds reached their highest diversity ever in the course of this epoch.
Brown algae plants, called kelp, proliferate, supporting new species of sea life, including otters, fish and various invertebrates. The cetaceans diversified, and some modern genera appeared, such as the sperm whales. The pinnipeds, which appeared near the end of the Oligocene, became more aquatic.
Perhaps most important were the 100 or so species of apes that lived during this time. They occupied much of the Old World and ranged in size, diet, and anatomy. Due to scanty fossil evidence it is unclear which ape or apes contributed to the modern hominoid clade, but molecular evidence indicates this ape lived from between 15 to 12 million years ago.
In the second epoch of the Hologene, the change to a cooler, dry, seasonal climate had considerable impacts on Pliocene vegetation, reducing tropical species world-wide. Deciduous forests proliferated, coniferous forests and tundra covered much of the north, and grasslands spread on all continents (except Antarctica). Tropical forests were limited to a tight band around the equator, and in addition to dry savannahs, deserts appeared in Asia and Africa.
In North America, rodents, large mastodonts and gomphotheres, and opossums continued successfully, while hoofed animals (ungulates) declined, with camel, deer and horse all seeing populations recede. Rhinos, tapirs and chalicotheres went extinct. Carnivores including the weasel family diversifed, and dogs and fast-running hunting bears did well. Ground sloths, huge glyptodonts and armadillos came north with the formation of the Isthmus of Panama.
In Eurasia rodents did well, while primate distribution declined. Elephants, gomphotheres and stegodonts were successful in Asia, and hyraxes migrated north from Africa. Horse diversity declined, while tapirs and rhinos did fairly well. Cows and antelopes were successful, and some camel species crossed into Asia from North America. Hyaenas and early saber-toothed cats appeared, joining other predators including dogs, bears and weasels. Human evolution during the Pliocene
Africa was dominated by hoofed animals, and primates continued their evolution, with australopithecines (some of the first hominids) appearing in the late Pliocene. Rodents were successful, and elephant populations increased. Cows and antelopes continued diversification and overtaking pigs in numbers of species. Early giraffes appeared, and camels migrated via Asia from North America. Horses and modern rhinos came onto the scene. Bears, dogs and weasels (originally from North America) joined cats, hyaenas and civets as the African predators, forcing hyaenas to adapt as specialized scavengers.
South America was invaded by North American species for the first time since the Cretaceous, with North American rodents and primates mixing with southern forms. Litopterns and the notoungulates, South American natives, did well. Small weasel-like carnivorous mustelids and coatis migrated from the north. Grazing glyptodonts, browsing giant ground sloths and smaller armadillos did well.
The marsupials remained the dominant Australian mammals, with herbivore forms including wombats and kangaroos, and the huge diprotodonts. Carnivorous marsupials continued hunting in the Pliocene, including dasyurids, the dog-like thylacine and cat-like Thylacoleo. The first rodents arrived, while bats did well, as did ocean-going whales. The modern platypus, a monotreme, appeared.
The predatory phorusrhacids were rare in this time; among the last was Titanis, a large phorusrhacid that rivaled mammals as top predators. Its distinct featured was it claws, which was re-evolved for grasping prey, such as Hipparion. Other birds probably evolved at this time, some are modern, some are now extinct.
Alligators and crocodiles died out in Europe as the climate cooled. The fossilized remains of a crocodile that measured longer than 27 feet and lived 2 million to 4 million years ago has been found in Kenya. Venomous snakes genera continued to increase as more rodents and birds evolved. Oceans continued to be relatively warm during the Pliocene, though they continued cooling. The Arctic ice cap formed, drying the climate and increasing cool shallow currents in the North Atlantic. Deep cold currents flowed from the Antarctic.
The formation of the Isthmus of Panama about 3.5 million years ago cut off the final remnant of what was once essentially a circum-equatorial current that had existed since the Cretaceous and the early Cenozoic. This may have contributed to further cooling of the oceans worldwide.
The Pliocene seas were alive with sea cows, seals and sea lions.
Earliest Hominid Toolmakers
Kenyanthropus platyops or Australopithecus Afarensis may have been the species of hominids that made the 3.3 million year old stone tools found in Northwest Kenya in 2015. The stone flakes and stone hammers were dated by several methods. This sets tool making for hominids about 700,000 years before Homo Habilis, once thought to have been the first hominid tool maker.
The relationship between grass and the ancestors of humans
True grasses did not evolve in the plant kingdom until around 65 million years ago. However, by 7 million years ago their impact on the world’s landscapes was notable. Vast forests in many areas around the world had rapidly given way to expansive grassland regions. As mentioned in the main section of the Neogene Period above, this expansion of grassland was encouraged by the cooling of the global temperatures. One of these new grassland areas was the African savannah where human ancestors had enjoyed an arboreal life in the forests.
The trees, diminishing in numbers were slowly becoming overpopulated with great apes in search of food and refuge. These great apes were faced with a choice. Stay in the trees and become ever hungrier, or brave locomotion across the emerging grasslands to seek food and refuge elsewhere.
Many animals exploited the grasslands themselves for nourishment which was great for the herbivores of the world, but also caused an evolutionary pulse which gave rise to new omnivorous and carnivorous animals. One of the herbivorous animals was the great ape ancestor of humans. It was essential to have an awareness of predators while foraging and moving through the grasslands, so those hominids that were able to balance and move around on their hind legs only had an advantage.
In a world of survival of the fittest, those that mastered the ability to walk on two legs thus increasing their height and freeing their front limbs for foraging would prevail and evolve.
Important Hominid Fossils
- 21 Ma A fossil of a creature called Morotopithecus bishopi, a tree-dwelling, ape-like creature that lived in what is now Uganda, was found in the 1960s and indicated that its transverse process had moved backward, behind the opening for the spinal cord. In 2007 Dr. Aaron Filler authored "The Upright Ape: a new origin of the Species," in which he argued that this common ancestor, and ancestors going back many millions of years before, walked upright. Homo sapiens, the human species, continued upright, while apes evolved back toward all fours.
- 20 Ma The gorilla lineage evolved from a common ancestor of orangutans about this time.
- 18 Ma Proconsul africanus fossil found by Mary Leakey
- 18 Ma - KNM RU 7290 Proconsul africanus found 1948 in Rusinga Island in Lake Victoria, Kenya by Mary Leakey
- 16-18 Ma - KNM WK 16999 Afropithecus turkanensis found 1986 in Kenya by Richard Leakey
- 12 Ma Gorilla and chimpanzees split from a common ancestor about this time.
- 10 Ma In 2007 Ethiopian fossil hunter found molars of a large ape that bespoke gorilla origins from about this time. They named the large ape Chororapithecus abyssinicus.
- 10.5-12.5 Ma - GSP 15000 Sivapithecus indicus found 1979 in Pakistan by D. Pilbeam and S. M. Ibrahim Shah
- 9.8 - Kenya - In 2007 Researchers in Kenya unveiled a 10-million-year-old jaw bone they believe belonged to a new species of great ape that could be the last common ancestor of gorillas, chimpanzees and humans. A Kenyan and Japanese team found the fragment, dating back to between 9.8 and 9.88 million years, in 2005 along with 11 teeth. The fossils were unearthed in volcanic mud flow deposits in the northern Nakali region of Kenya.
- 9 Ma - The first creatures in the human lineage lived about this time.
- 8.5 Ma The oldest trace in Sardinia of the anthropomorphic prehistoric primate called Oreopithecus bambolii
- 8 Ma - IGF 11778 Oreopithecus bambolii found 1872 in Italy by Paul Gervais
- 8 Ma - IVPP PA644 ? Lufengpithecus found 1978 in China
- 7 Ma - TM 266 (Toumai) Sahelanthropus tchadensis found 2001 in Chad by Alain Beauvilain, Fanone Gongdibe, Mahamat Adoum and Ahounta Djimdoumalbaye. Possibly very close to the time of the chimpanzee/human divergence, and so it is unclear whether it can be regarded as a member of the Hominini tribe
- 6 Ma - BAR 1000'00 Orrorin tugenensis (millenium man) found 2000 in Kenya by Martin Pickford, Kiptalam Cheboi, Dominique Gommery, Pierre Mein, Brigitte Senut
- Humans, chimps and bonobos all share a common ancestor that lived about 6 million years ago in Africa.
- 5.5 Ma - KNM-LT 329 Australopithecus anamensis found 1967 in Lothagam, Turkana District, Kenya by Arnold Lewis
- 4.15-5.25 Ma - KNM-TH 13150 Australopithecus anamensis found 1984 in Tabarin (KO77 ?), Kenya by Kiptalam Cheboi
- 4.4 Ma A partial skeleton in more than 90 pieces was found by a group led by Tim White, Gen Suwa and Berhane Asfaw in the Middle Awash at Aramis, Ethiopia, in late 1994. They name it Ardipithecus ramidus, which put it in a new genus and means ground ape root. A new argon-argon dating technique was used.
- 5.5 Ma to 4.4 Ma - Ardi Ardipithecus ramidus found 1994 in Middle Awash, Ethiopia by Yohannes Haile Selassie
- 4 Ma - KNM-KP 271 Australopithecus anamensis found 1965 in Kanapoi, Turkana District by Bryan Patterson
- 3.7 Ma - Laetoli Footprints Bipedal hominid found 1976 in Tanzania by Mary Leakey
- 3.7 Ma - Sterkfontein fossil, 'Little Foot' is Lucy ancestor. Found by Ronald J. Clarke in 1994.
- 3.6 - 3.8 Ma - LH 4 Australopithecus afarensis found 1974 in Tanzania by Donald Johanson
- 3.6 Ma - Abel Australopithecus bahrelghazali found by Michel Brunet in the Bahr el Ghazal valley near Koro Toro, in Chad
- 3.5 Ma - KNM WT 40000 Kenyanthropus platyops found 1999 in Kenya by Justus Erus (possible direct human ancestor)
- 3.4 Ma - First evidence of tool use. The journal Nature reports that newly discovered tool marks on bones indicates that we were using tools at minimum 800,000 years earlier than previously thought. This places the start of tool use at 3.4 million years ago or earlier. The most likely ancestor in this time frame would be Australopithecus afarensis.
- 3.4 Ma - Burtele partial foot (BRT-VP-2/73) showed that A. Afarensis was not alone. This species apparently clung to trees rather than use bipedalism for locomotion.
- 3.4 Ma Australopithecus deyiremeda found in the Afar region of Ethiopia. May be concurrent with "Lucy"
- 3.4 Ma - Ethiopia - Australopithecus Afarensis represented in the earliest find at Hadar in 1974 in the skeleton nicknamed, "Lucy" and again in 2006 by a juvenile, perhaps aged 3, nicknamed "Dikika Girl" found in the Dikika region of Ethiopia. It's believed that these small hominids walked upright, but had strong shoulder "ape-like" blades and long arms adapted for tree climbing and swinging.
- 3.3 Ma - Stw 573 (Little foot) Australopithecus ? found 1994 in South Africa by Ronald J. Clarke
- 3.3 Ma - DIK-1 (Selam) Australopithecus afarensis found 2000 in Ethiopia by Zeresenay Alemseged
- 3 - 3.2 Ma - AL 200-1 Australopithecus afarensis found 1975 in Ethiopia by Donald Johanson Yves Coppens and Maurice Taieb
- 3 - 3.2 Ma - AL 129-1 Australopithecus afarensis found 1973 in Ethiopia by Donald Johanson
- 3 Ma - Teeth of Australopithecus africanus analyzed from this period indicate consumption of large quantities of carbon 13 from either grasses and sedges of animals that ate such plants or both. This was a transition period of movement from trees and forests to more open land.
- Two primate species of monkey, mantled howler monkeys and black howler monkeys, diverged about 3 million years ago in Mexico
- K 12 (Abel) Australopithecus bahrelghazali found 1995 in Chad by Michel Brunet
- 3.2 Ma - AL 288-1 (Lucy) Australopithecus afarensis found 1974 in Ethiopia by Donald Johanson, Yves Coppens and Maurice Taieb
- 3 Ma - AL 444-2 Australopithecus afarensis found 1991 in Ethiopia by Bill Kimbel
- 2.8 Ma LD 350-1, Earliest homo fossil left side of the lower jaw along with five teeth, from the Afar region of Ethiopia.
- 2.6 - 2.8 Ma - STS 5 (Mrs. Ples) Australopithecus africanus found 1947 in South Africa by Robert Broom
- 2.6-2.8 Ma - STS 14 Australopithecus africanus found 1947 in South Africa by Robert Broom
- 2.5Ma - STS 52 Australopithecus africanus found 1947 in South Africa by Robert Broom
- 2.5 Ma - STS 71 Australopithecus africanus found 1947 in South Africa by Robert Broom
- 2.5 Ma - Taung 1 (Taung Child) Australopithecus africanus found 1924 in South Africa by Raymond Dart - Average age of sample teeth is 22 years at death, as analyzed by Alan Mann. In 2006 new analysis of the Taung skull suggested that the child was killed by a predatory bird.
- 2.5 Ma - KNM WT 17000 (The Black Skull) Paranthropus aethiopicus found 1985 in Kenya by Alan Walker
- 2.5 Ma - Australopithecus garhi, Hatayae Member of the Bouri Formation, Ethiopia
- 2.3 Ma - primitive stone tools were used to scavenge kills made by other predators, and harvest carrion for their bones and marrow. In hunting, Homo habilis was probably not capable of competing with large predators, and was still more prey than hunter, although Homo habilis probably did steal eggs from nests, and may have been able to catch small game, and weakened larger prey (cubs and older animals). The tools were classed as Oldowan.
- 2.3 Ma Australopithecus boisei (an older find) from Omo, Ethiopia.
- 2-2.04 Ma - Wushan Man Homo erectus found 1986 in China
- 2.3 Ma to 1 Ma - Ethiopia - Homo habilis Homo habilis is the first hominoid to bear the distinction of being classified as Homo. Homo habilis had a larger brain and a more varied diet that, for the first time, included meat. Homo habilis ("Man the tool maker") was named thusly because of association with early tool creation, stone choppers and other stone tools. These may have been used to crack open bones to access the marrow. They were once thought to be the first tools but this date has been pushed back another 700,000 years.
- 2 Ma - TM 1517 Paranthropus robustus found 1938 in South Africa by Gert Terblanche
Australopithecines and the beginning of the Stone Age
Paleoanthropolgists generally believe that australopithecines evolved from an earlier creature called the ardipithicus of which dozens of fosilised bones have been discovered from the 1990s onwards. The more recently evolved australophithicus was discovered around twenty years previous and the discoveries are in more abundant numbers.
A number of fossils that have been labelled as australopithecine species have been discovered. Scientific examination has evidentially suggested that they lived between 4.2 and 2 million years ago, although the first ever australopithecine may have lived a lot earlier.
The australopithecines are members of the hominini tribe. The relevance of this information is crucial to anybody with an interest in evolution, in particularly of the human, as humans and more specifically homo sapiens are the only extant species of animal within this tribe. Our closest living relative, the chimpanzee, diverged from the human evolutionary tree before the existence of any discovered hominini tribe member. It must be noted that certain individuals have suggested that chimpanzees are within the hominini tribe, however this is not a general view currently.
The hominini tribe should not be confused with the more ambiguous homininae subfamily, members of which are referred to as hominines. The hominini tribe is however a part of the hominine subfamily.
Australopithecine appearance was small and ape-like with plenty of body hair. Their brains are approximately the same size as those of modern chimpanzees, and they are believed to have used basic hand tools which were manufactured for use. This manufacturing ability is believed to only have ever existed within the homininae subfamily. Tools that date back to the crossover of the Neogene to the Quarternary Period have been found in various places, but initially at the famed Olduvai Gorge, which lends its name to these discovered tools of this period called Oldowan tools. An example of these tools would include handaxes which were shaped by methodically striking larger stones with hammerstones which resulted in a sharp edged stone flake which could be used for cutting, piercing or scraping.
These tools were made from silicate minerals, a combination of silicon and oxygen which crystallises and collectively form rocks. These two elements make up approximately 75% of all the elements of Earth’s crust. Silicon is one of the elements created from the molecule fusing factories of a sun’s core, and is one of the elements that are thrown out into space when a sun dies.
The ability to create these tools was the start of the Stone Age.
One of the most complete and famous discoveries of an australopithecine was in 1974 when a species catagorised as Australopithecus afarensis was uncovered by Donald Johanson and his team while exploring near Hadar in Ethiopia in the Afar Depression in east Africa. This skeleton was nicknamed Lucy, which is how she is commonly referred to today. Her name was given to her directly from The Beatles’ well known rock song “Lucy In The Sky With Diamonds”. Geologists believe they can normally date such skeletons within a 20,000 year time range by examining the rocks surrounding the fossil. Lucy has been dated at about 3.18 million years old.
Other genera closely associated with Australopithecines include Paranthropus.
The obvious question has to be, “What is encephalization?”, and further to that “What is its significance in hominin evolution towards the end of the Neogene Period?”.
To answer these questions, we firstly have to address the fact that humankind during its history has noticed that the size of a human brain appears to be large compared to its body size than it does in other mammals. Famous public references to this have been made by the philosopher Aristotle (384-322 BC) and the naturalist Charles Darwin (1809-1892).
Some scientists firmly believe that brain ratio compared to body ratio has a direct relationship to intelligence. Scientific study has shown that this is almost incomparably more likely when comparing mass ratio than with volume ratio, although other criteria need to be applied to make a formula truly authentic.
The answer to our original questions; encephalization is when a brain mass increases in ratio to its body mass, and a fine example of this is in hominin evolution towards the end of the Neogene Period.
The australopithecines, the most likely direct ancestors of humans had a brain mass roughly 70 to 80 per cent of homo habilis, which is arguably the first truly human species to be present on Earth. This raises the question, “Why was encephalization so dramatic between these animals?”.
Not only was there dramatic encephalization between these animals but it notably continued throughout homo evolution to this present day. The most likely protagonist for the cause is protein which has been scientifically shown to enhance cognitive ability.
So it is believed that encephalization has a relationship with diet, and as homo diet improved, homo stomachs became smaller and homo brains became larger. It is hypothesised to be a form of tissue exchange. In other words, the concentration of tissue formation changed its concentration to brain formation from stomach formation.
However, a further theory has arisen that would relate to encephalization revolving around conditions and climate. Some would have us believe that the necessity to co-exist in the challenging conditions away from the African continent made encephalization a key ingredient to survival.
Nonetheless, it is taken for granted that encephalization has been an important trait of hominine evolution in the last seven million years, and while debate goes on about the reasoning behind it, it certainly makes us what we are today. It has given humans the ability to remember information and organise our coexistence with one another socially and therefore adapt its abilities to exist in the more unnatural climates of areas of the globe that it emmigrated to.
Approximately 5.332 million years BP, the Pliocene epoch begins. Most eruptions before the Quaternary period have an unknown VEI.
- Boring Lava Field, Boring, Oregon, USA; the zone became active at least 2.7 Ma, and has been extinct for about 300,000 years.
- Norfolk Island, Australia; remnant of a basaltic volcano active around 2.3 to 3 Ma.
- Pastos Grandes Caldera (size: 40 x 50 km), Altiplano-Puna Volcanic Complex, Bolivia; 2.9 Ma; VEI 7; more than 820 cubic kilometers (197 cu mi) of Pastos Grandes Ignimbrite.
- Little Barrier Island, northeastern coast of New Zealand's North Island; it erupted from 1 million to 3 Ma.
- Mount Kenya; a stratovolcano created approximately 3 Ma after the opening of the East African rift.
- Pacana Caldera (size: 60 x 35 km), Altiplano-Puna Volcanic Complex, northern Chile; 4 Ma; VEI 8; 2,500 cubic kilometers (600 cu mi) of Atana Ignimbrite.
- Frailes Plateau, Bolivia; 4 Ma; 620 cubic kilometers (149 cu mi) of Frailes Ignimbrite E.
- Cerro Galán (size: 32 km wide), Catamarca Province, northwestern Argentina; 4.2 Ma; 510 cubic kilometers (122 cu mi) of Real Grande and Cueva Negra tephra.
- Yellowstone hotspot, Heise volcanic field, Idaho; Kilgore Caldera (size: 80 x 60 km); VEI 8; 1,800 cubic kilometers (432 cu mi) of Kilgore Tuff; 4.45 Ma ±0.05.
- Kari Kari Caldera, Frailes Plateau, Bolivia; 5 Ma; 470 cubic kilometers (113 cu mi) of tephra.
Approximately 23.03 million years BP, the Neogene period and Miocene epoch begin.
- Lord Howe Island, Australia; Mount Lidgbird and Mount Gower are both made of basalt rock, remnants of lava flows that once filled a large volcanic caldera 6.4 Ma.
- Yellowstone hotspot, Heise volcanic field, Idaho; 5.51 Ma ±0.13 (Conant Creek Tuff).
- Yellowstone hotspot, Heise volcanic field, Idaho; 5.6 Ma; 500 cubic kilometers (120 cu mi) of Blue Creek Tuff.
- Cerro Panizos (size: 18 km wide), Altiplano-Puna Volcanic Complex, Bolivia; 6.1 Ma; 652 cubic kilometers (156 cu mi) of Panizos Ignimbrite.
- Yellowstone hotspot, Heise volcanic field, Idaho; 6.27 Ma ±0.04 (Walcott Tuff).
- Yellowstone hotspot, Heise volcanic field, Idaho; Blacktail Caldera (size: 100 x 60 km), Idaho; 6.62 Ma ±0.03; 1,500 cubic kilometers (360 cu mi) of Blacktail Tuff.
- Pastos Grandes Caldera (size: 40 x 50 km), Altiplano-Puna Volcanic Complex, Bolivia; 8.3 Ma; 652 cubic kilometers (156 cu mi) of Sifon Ignimbrite.
- Manus Island, Admiralty Islands, northern Papua New Guinea; 8–10 Ma
- Banks Peninsula, New Zealand; Akaroa erupted 9 Ma, Lyttelton erupted 12 Ma.
- Mascarene Islands were formed in a series of undersea volcanic eruptions 8-10 Ma, as the African plate drifted over the Réunion hotspot.
- Yellowstone hotspot, Twin Fall volcanic field, Idaho; 8.6 to 10 Ma.
- Yellowstone hotspot, Picabo volcanic field, Idaho; 10.21 Ma ± 0.03 (Arbon Valley Tuff).
- Mount Cargill, New Zealand; the last eruptive phase ended some 10 Ma. The center of the caldera is about Port Chalmers, the main port of the city of Dunedin.
- Yellowstone hotspot, Idaho; Bruneau-Jarbidge volcanic field; 10.0 to 12.5 Ma (Ashfall Fossil Beds eruption).
- Anahim hotspot, British Columbia, Canada; has generated the Anahim Volcanic Belt over the last 13 million years.
- Yellowstone hotspot, Owyhee-Humboldt volcanic field, Nevada/ Oregon; around 12.8 to 13.9 Ma.
- Campi Flegrei, Naples, Italy; 14.9 Ma; 79 cubic kilometers (19 cu mi) of Neapolitan Yellow Tuff.
- Huaylillas Ignimbrite, Bolivia, southern Peru, northern Chile; 15 Ma ±1; 1,100 cubic kilometers (264 cu mi) of tephra.
- Yellowstone hotspot, McDermitt ? volcanic field (North), Trout Creek Mountains, Whitehorse Caldera (size: 15 km wide), Oregon; 15 Ma; 40 cubic kilometers (10 cu mi) of Whitehorse Creek Tuff.
- Yellowstone hotspot (?), Lake Owyhee volcanic field; 15.0 to 15.5 Ma.
- Yellowstone hotspot, McDermitt volcanic field (South), Jordan Meadow Caldera, (size: 10–15 km wide), Nevada/ Oregon; 15.6 Ma; 350 cubic kilometers (84 cu mi) Longridge Tuff member 2-3.
- Yellowstone hotspot, McDermitt volcanic field (South), Longridge Caldera, (size: 33 km wide), Nevada/ Oregon; 15.6 Ma; 400 cubic kilometers (96 cu mi) Longridge Tuff member 5.
- Yellowstone hotspot, McDermitt volcanic field (South), Calavera Caldera, (size: 17 km wide), Nevada/ Oregon; 15.7 Ma; 300 cubic kilometers (72 cu mi) of Double H Tuff.
- Yellowstone hotspot, McDermitt volcanic field (South), Hoppin Peaks Caldera, 16 Ma; Hoppin Peaks Tuff.
- Yellowstone hotspot, McDermitt volcanic field (North), Trout Creek Mountains, Pueblo Caldera (size: 20 x 10 km), Oregon; 15.8 Ma; 40 cubic kilometers (10 cu mi) of Trout Creek Mountains Tuff.
- Yellowstone hotspot, McDermitt volcanic field (South), Washburn Caldera, (size: 30 x 25 km wide), Nevada/ Oregon; 16.548 Ma; 250 cubic kilometers (60 cu mi) of Oregon Canyon Tuff.
- Yellowstone hotspot (?), Northwest Nevada volcanic field (NWNV), Virgin Valley, High Rock, Hog Ranch, and unnamed calderas; West of Pine Forest Range, Nevada; 15.5 to 16.5 Ma.
- Yellowstone hotspot, Steens and Columbia River flood basalts, Pueblo, Steens, and Malheur Gorge-region, Pueblo Mountains, Steens Mountain, Washington, Oregon, and Idaho, USA; most vigorous eruptions were from 14–17 Ma; 180,000 cubic kilometers (43,184 cu mi) of lava.
- Mount Lindesay (New South Wales), Australia; is part of the remnants of the Nandewar extinct volcano that ceased activity about 17 Ma after 4 million years of activity.
- Oxaya Ignimbrites, northern Chile (around 18°S); 19 Ma; 3,000 cubic kilometers (720 cu mi) of tephra.
- Pemberton Volcanic Belt was erupting about 21 to 22 Ma.
The digestive enzyme ADH4 ?, which begins to break down alcohol on the tongue and in the esophagus and continues to do so in the stomach, was first found plentifully in the gorilla, a primate ancestor from whose lineage humans diverged roughly 10 million years ago. It is similarly found in more recent evolutionary ancestors, including the chimpanzee and the bonobo.
3 million year ago the Arctic was dotted with forests. Sea levels were 80 feet (24 meters) higher than they are currently. The average temperate was about 2 degrees C warmer than today. CO2 ? levels were about 400 parts for every million parts of air in the mid-Pliocene compared to 383.1 parts per million in 2007. The causes of the ancient warming are not completely understood. They are believed to be a combination of increased greenhouse gases from natural sources and a greater impact by ocean currents in moving warm water to cold regions.
The Vredefort Dome was created over 2,000 million years ago South-West of Johannesburg when a meteorite struck earth. It is the oldest crater made by either a meteorite or a comet and it is reportedly the site of the largest energy release in the world’s history.
It is believed that early hominids emerged in this era. The family Hominidae diverged from the Hylobatidae (Gibbon) family 15-20 million years ago. around 14 million years ago, the Ponginae (orangutans), diverged from the Hominidae family. Bipedalism is the basic adaption of the Hominin line, and the earliest bipedal Hominin is considered to be either Sahelanthropus or Orrorin, with Ardipithecus, a full bipedal, coming somewhat later. The gorilla and chimpanzee diverged around the same time, about 4-6 million years ago, and either Sahelanthropus or Orrorin may be our last shared ancestor with them. The early bipedals eventually evolved into the australopithecines and later the genus Homo.
Humans, chimps and bonobos all share a common ancestor that lived about 6 million years ago.
Evidence of this is supported by fossil specimens uncovered on this continent.
Sahelanthropus fossils were discovered in Chad between 2001 and 2002, and are believed to have existed around 7 million years ago.
Orrorin fossils were discovered in the Lukeino Formation in Kenya from 2000 and are believed to have existed around 6 million years ago.
Ardipithecus fossils were discovered in Ethiopia from 1994 and are believed to have existed around 5 million years ago.
These three genera are all hominids. In other words they are great apes. However, it is clear that they all closely relate to the human and chimpanzee divergence. It is debated where all of them exactly fit into the evolutionary family tree, but they have given a good insight into the emergence of bipedal locomotion (the ability to walk on two legs), and into what pre-proto-human species may have looked like.
For a timeline of important discoveries relating to this period of history see the section above called "Important Hominid Fossils".
The fossilized remains of a crocodile that measured longer than 27 feet and lived 2 million to 4 million years ago has been found in Kenya.
The earliest documented members of the genus Homo are Homo habilis which evolved around 2.3 million years ago; the earliest species for which there is positive evidence of use of stone tools. The brains of these early hominins were about the same size as that of a chimpanzee.
At Olduvai Gorge, research was done to identify which plants dominated the local environment around 2 million years ago. Researchers from Pennsylvania State University looked at tough leaf wax because they survive well in the sediment. The result points to the fact that the area changed a number of times over a 200,000 year period between grasslands and forest, dry and wet climates. It's believed that this may have pushed hominid evolution by creating environmental stresses that required adaptation.
Archaelogical evidence suggests that Homo erectus lived in China from the period beginning 2.24 billion years ago.
Ailuractos from the Late Miocene in China, about 7-8 million years ago, was once thought to be the oldest known member of the panda family. Earlier fossils from 11.6 Mya were found in Spain.
11.6 Million Years Ago
Two fossilized mandibles and several teeth found in northeastern Spain date from 11.6 million years ago are the oldest remains found to date of ancestors of the giant panda.
5.3 million years ago The refilling of the Mediterranean Sea
A catastrophic flood refilled the Mediterranean Sea 5.3 million years ago, at the beginning of the Zanclean age that ended the Messinian salinity crisis. The flood occurred when Atlantic waters found their way through the Strait of Gibraltar into the desiccated Mediterranean basin, following the Messinian salinity crisis during which it repeatedly became dry and re-flooded, dated by general consensus to before the emergence of modern humans
There was a meteor impact in Nördlingen Ries leaving an impact crater of about 25km.
Greenland was once green and wooded before ice covered it for millions of years. Research on the ice fields have shown strong concentrations of beryllium, nitrogen and carbon giving rise to the theory that Greenland had been exposed for at least a million years.
21 Million Years Ago
Monkeys resembling today's capuchins accomplished the astonishing feat of crossing at least 100 miles (160 km) of open ocean 21 million years ago to get from South America to North America eons before the two continents joined together.
Scientists reached that conclusion based on the discovery of seven teeth during excavations involving the Panama Canal's expansion, showing monkeys had reached the North American continent far earlier than previously known.
The teeth belonged to Panamacebus transitus, a previously unknown medium-sized monkey species.
12 Million Years Ago
The Yellowstone Hotspot erupted (Bruneau-Jarbidge) Responsible for the Ashfall Fossil Beds 1,600 km to the east.
6 Million Years Ago
The Yellowstone Hotspot erupted (Blacktail Tuff) 1,500 km³ ejecta
Titanis walleri, also "Terror Birds", a species of very large predatory flightless bird, lived approximately 5-1.8 million years ago (Pliocene) in North America, fossil evidence having been found in Florida and Texas.
4.4 Million Years Ago
The Salton Sea region was part of the Gulf of California until about 4.4 million years ago. The Colorado River silt eventually blocked off the gulf and separated the region from the Pacific Ocean.
The Yellowstone Hotspot erupted (Kilgore Tuff) 1,800 km³ ejecta.
In the permafrost of Canada ancient horse DNA has pushed the common ancestors to horses, zebras and donkeys back to this period.
The Grand Canyon
Geologists have discovered that the formation of this natural wonder caused by the continual flowing of the Colorado River through the Colorado Plateau dates back around 17 million years, around 3 times as long ago as previously thought.
The Colorado River has exposed one of the most astonishing pictures of Earth history with this relatively recent cause to erode land by revealing rocks dating back two billion years.
The formation of the Isthmus of Panama
North America and South America separated from the supercontinent of Pangaea as separate landmasses roughly between 175 and 140 million years ago. They remained separate until the formation of the Isthmus of Panama which joined the two landmasses together as a land bridge, thought to have been completed around 3 to 4 million years ago.
Speculation of the existence of a Panama peninsula of North America has been supported by the discovery of 19 million year old mammalian bone fossils in this area. It is thought that initially the sea bed between the two continents was raised and islands appeared from beneath the sea.
A combination of the continual rising of the sea bed with the gathering of sediment from the sea by these existing islands could be the explanation for the completion of the land bridge.
The formation of this Isthmus has served as a diverting influence on the warm ocean current called the Gulf Stream. Initially a current which crossed the South Atlantic Ocean from the African continent and passed between North and South America into the Pacific Ocean, it is now nursed around the Gulf of Mexico and back across the North Atlantic Ocean towards Europe. This proved to be a major effect on North American and western European climate.
The Siberian unicorn first emerged in the fossil record around 2.5 million years ago, and disappeared about 29,000 years ago. It weighed about 9,000 lbs and was more closely similar to a rhino than a horse.
Popularly known as ‘terror birds,’ phorusrhacids are an extinct clade, or branch, of giant flightless, meat-eating birds that were the dominant predators in South American for tens of millions of years. These enormous birds, which stood up to 10 feet (3 meters) tall and had large hooked beaks, became extinct about 2.5 million years ago.
A supervolcano located at La Pacana Complex in the Antofagasta Region, northern of Chile eruption c. 4 million years ago produced 2,500 cubic kilometers (600 cu mi) of tephra.
2.5 Million Years Ago Cerro Galan, in Argentina, erupted with approximately 1,050 km³ of ejecta.
The islands of Kauai and Niihau date back to 5 million years ago. The entire chain is older, but these are the oldest of the existing main islands.
In 2002, astronomers discovered that roughly 2 million years ago, around the end of the Pliocene epoch, a group of bright O and B stars called the Scorpius-Centaurus OB association passed within 150 light-years of Earth and that one or more supernovae may have occurred in this group at that time. Such a close explosion could have damaged the Earth's ozone layer and caused the extinction of some ocean life (consider that at its peak, a supernova of this size could produce that same amount of absolute magnitude as an entire galaxy of 200 billion stars).
- Visual History of the World, National Geographic, 2005.
- The Horse: The Epic History of Our Noble Companion, Wendy Williams, Scientific American / Farrar, Straus and Giroux, 2015, Pages: 55-56, 88-89, 114-115