![adsertoris:
world-shaker:
If the Life of the Earth was reduced to a 24 hour clock
The age of the Earth is 4.54 billion years (4.54 × 109 years ± 1%).[1][2][3] This age is based on evidence from radiometric age dating of meteorite material and is consistent with the ages of the oldest-known terrestrial and lunar samples. Following the scientific revolution and the development of radiometric age dating, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old.[4]
The oldest such minerals analyzed to date – small crystals of zircon from the Jack Hills of Western Australia – are at least 4.404 billion years old.[5][6][7] Comparing the mass and luminosity of the Sun to the multitudes of other stars, it appears that the solar system cannot be much older than those rocks. Ca-Al-rich inclusions (inclusions rich in calcium and aluminium) – the oldest known solid constituents within meteorites that are formed within the solar system – are 4.567 billion years old,[8][9] giving an age for the solar system and an upper limit for the age of Earth.
It is hypothesised that the accretion of Earth began soon after the formation of the Ca-Al-rich inclusions and the meteorites. Because the exact accretion time of Earth is not yet known, and the predictions from different accretion models range from a few millions up to about 100 million years, the exact age of Earth is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages.
—
Current models in the origin of life
Origin of organic molecules
“Soup” theory today: Miller’s experiment and subsequent work
The deep sea vent theory
Fox’s experiments
Eigen’s hypothesis
Hoffmann’s contributions
Wächtershäuser’s hypothesis
Radioactive beach hypothesis
Thermodynamic origin of life: ultraviolet and temperature-assisted replication (UVTAR) model
Models to explain homochirality
Self-organization and replication
From organic molecules to protocells
The RNA world
“Metabolism first” models
Other models
Main article: Timeline of evolution
Morse and MacKenzie have suggested that oceans may have appeared first in the Hadean eon, as soon as two hundred million years (200 Ma) after the Earth was formed, in a hot 100 °C (212 °F) reducing environment, and that the pH of about 5.8 rose rapidly towards neutral.[23] This has been supported by Wilde[3] who has pushed the date of the zircon crystals found in the metamorphosed quartzite of Mount Narryer in Western Australia, previously thought to be 4.1–4.2 Ga, to 4.404 Ga. This means that oceans and continental crust existed within 150 Ma of Earth’s formation.
Despite this, the Hadean environment was one highly hazardous to life. Frequent collisions with large objects, up to 500 kilometres (310 mi) in diameter, would have been sufficient to vaporise the ocean within a few months of impact, with hot steam mixed with rock vapour leading to high altitude clouds completely covering the planet. After a few months the height of these clouds would have begun to decrease but the cloud base would still have been elevated for about the next thousand years. After that, it would have begun to rain at low altitude. For another two thousand years rains would slowly have drawn down the height of the clouds, returning the oceans to their original depth only 3,000 years after the impact event.[24]
Between 3.8 and 4.1 Ga, changes in the orbits of the gaseous giant planets may have caused a late heavy bombardment that pockmarked the moon and other inner planets (Mercury, Mars, and presumably Earth and Venus). This would likely have sterilized the planet, had life appeared before that time.
By examining the time interval between such devastating environmental events, the time interval when life might first have come into existence can be found for different early environments. The study by Maher and Stevenson shows that if the deep marine hydrothermal setting provides a suitable site for the origin of life, abiogenesis could have happened as early as 4.0 to 4.2 Ga, whereas if it occurred at the surface of the earth abiogenesis could only have occurred between 3.7 and 4.0 Ga.
This timeline of the evolution of life outlines the major events in the development of life on the planet Earth (See Organism). For a thorough explanatory context, see the history of Earth, and geologic time scale. The dates given in this article are estimates based on scientific evidence.
The basic timeline is a 4.5 billion year old Earth, with (very approximate) dates:
3.8 billion years of simple cells (prokaryotes),
3 billion years of photosynthesis,
2 billion years of complex cells (eukaryotes),
1 billion years of multicellular life,
600 million years of simple animals,
570 million years of arthropods (ancestors of insects, arachnids and crustaceans),
550 million years of complex animals,
500 million years of fish and proto-amphibians,
475 million years of land plants,
400 million years of insects and seeds,
360 million years of amphibians,
300 million years of reptiles,
200 million years of mammals,
150 million years of birds,
130 million years of flowers,
65 million years since the non-avian dinosaurs died out,
2.5 million years since the appearance of the genus Homo,
200,000 years since humans started looking like they do today,
25,000 years since Neanderthals died out.
Detailed timeline
Ma, (“megaannum”) means “million years ago”. ka means “thousand years ago” and ya means “years ago” Hadean Eon
3800 Ma and earlier.
4600 Ma: The planet Earth forms from the accretion disc revolving around the young Sun.
Between 4500 and 3500 Ma: The earliest life appears, possibly derived from self-reproducing RNA molecules.[5][6] The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition, with natural selection favouring those molecules which are more efficient at replication. DNA molecules then take over as the main replicators and these archaic genomes soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: proto-cells.
3900 Ma Late Heavy Bombardment: peak rate of impact events upon the inner planets by meteoroids. This constant disturbance may have obliterated any life that had evolved to that point, or possibly not, as some early microbes could have survived in hydrothermal vents below the Earth’s surface;[10] or life might have been transported to Earth by a meteoroid.
Somewhere between 3900 and 2500 Ma Cells resembling prokaryotes appear.[12] These first organisms are chemoautotrophs: they use carbon dioxide as a carbon source and oxidize inorganic materials to extract energy. Later, prokaryotes evolve glycolysis, a set of chemical reactions that free the energy of organic molecules such as glucose and store it in the chemical bonds of ATP. Glycolysis (and ATP) continue to be used in almost all organisms, unchanged, to this day.
Archean Eon
3800 Ma – 2500 Ma
3500 Ma: Lifetime of the last universal ancestor; the split between bacteria and archaea occurs.
Bacteria develop primitive forms of photosynthesis which at first do not produce oxygen. These organisms generate ATP by exploiting a proton gradient, a mechanism still used in virtually all organisms.
3000 Ma: Photosynthesizing cyanobacteria evolve; they use water as a reducing agent, thereby producing oxygen as waste product. More recent research[citation needed], however, suggests a later time of 2700 Ma. The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The oxygen concentration in the atmosphere slowly rises, acting as a poison for many bacteria. The Moon is still very close to Earth and causes tides 1,000 feet (305 m) high. The Earth is continually wracked by hurricane-force winds. These extreme mixing influences are thought to stimulate evolutionary processes. (See Oxygen catastrophe)
Proterozoic Eon
2500 Ma – 542 Ma
By 1850 Ma Eukaryotic cells appear
By 1200 Ma Sexual reproduction first appears, increasing the rate of evolution.
1200 Ma: Simple multicellular organisms evolve, mostly consisting of cell colonies of limited complexity. First multicellular red algae evolve
850–630 Ma: A global glaciation may have occurred. Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution.
580–500 Ma: Most modern phyla of animals begin to appear in the fossil record during the Cambrian explosion. (A preserved specimen is called a “fossil” if it is older than some minimum age, most often the arbitrary date of 10,000 years ago. Hence, fossils range in age from the youngest at the start of the Holocene Epoch to the oldest from the Archaean Eon, up to 3.4 billion years old.)
580–540 Ma: The accumulation of atmospheric oxygen allows the formation of an ozone layer. This blocks ultraviolet radiation, permitting the colonisation of the land.
560 Ma Earliest fungi
550 Ma First fossil evidence for ctenophora (comb-jellies), porifera (sponges), and anthozoa (corals & anemones)
Phanerozoic Eon
542 Ma – present
The Phanerozoic Eon, literally the “period of well-displayed life”, marks the appearance in the fossil record of abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, which are divided by major mass extinctions.
Paleozoic Era
542 Ma – 251.0 Ma
535 Ma Major diversification of living things in the oceans: chordates, arthropods (e.g. trilobites, crustaceans), echinoderms, mollusks, brachiopods, foraminifers and radiolarians, etc.
530 Ma The first known footprints on land date to 530 Ma, indicating that early animal explorations may have predated the development of terrestrial plants.
485 Ma First vertebrates with true bones (jawless fishes).
450 Ma Land arthropod burrows (millipedes) appear, along with the first complete conodonts and echinoids.
434 Ma The first primitive plants move onto land,[33] having evolved from green algae living along the edges of lakes.[34] They are accompanied by fungi[citation needed], which may have aided the colonization of land through symbiosis.
420 Ma Earliest ray-finned fishes, trigonotarbid arachnids, and land scorpions.
363 Ma By the start of the Carboniferous Period, the Earth begins to be recognisable. Insects roamed the land and would soon take to the skies; sharks swam the oceans as top predators, and vegetation covered the land, with seed-bearing plants and forests soon to flourish.
Four-limbed tetrapods gradually gain adaptations which will help them occupy a terrestrial life-habit.
320 Ma Synapsids separate from sauropsids (reptiles) in late Carboniferous
280 Ma Earliest beetles, seed plants and conifers diversify while lepidodendrids and sphenopsids decrease. Terrestrial temnospondyl amphibians and pelycosaurs (e.g. Dimetrodon) diversify in species.
251.4 Ma The Permian-Triassic extinction event eliminates over 90-95% of marine species. Terrestrial organisms were not as seriously affected as the marine biota. This “clearing of the slate” may have led to an ensuing diversification, but life on land took 30M years to completely recover.
Mesozoic Era
From 251.4 Ma The Mesozoic Marine Revolution begins: increasingly well-adapted and diverse predators pressurise sessile marine groups; the “balance of power” in the oceans shifts dramatically as some groups of prey adapt more rapidly and effectively than others.
245 Ma Earliest ichthyosaurs.
225 Ma Earliest dinosaurs (prosauropods), first cardiid bivalves, diversity in cycads, bennettitaleans, and conifers. First teleost fishes.
220 Ma Gymnosperm forests dominate the land; herbivores grow to huge sizes in order to accommodate the large guts necessary to digest the nutrient-poor plants.[citation needed], first flies and turtles (Odontochelys). First Coelophysoid dinosaurs
215 Ma: First mammals (e.g. Eozostrodon), minor vertebrate extinctions occur
200 Ma: The first accepted evidence for viruses (at least, the group Geminiviridae) exists. Viruses are still poorly understood and may have arisen before “life” itself, or may be a more recent phenomenon.
Major extinctions in terrestrial vertebrates and large amphibians. Earliest examples of Ankylosaurian dinosaurs
155 Ma First blood-sucking insects (ceratopogonids), rudist bivalves, and cheilosome bryozoans. Archaeopteryx, a possible ancestor to the birds, appears in the fossil record, along with triconodontid and symmetrodont mammals. Diversity in stegosaurian and theropod dinosaurs.
130 Ma: The rise of the Angiosperms: These flowering plants boast structures that attract insects and other animals to spread pollen. This innovation causes a major burst of animal evolution through co-evolution. First freshwater pelomedusid turtles.
100 Ma Earliest bees.
90 Ma Extinction of ichthyosaurs. Earliest snakes and nuculanid bivalves. Large diversification in angiosperms: magnoliids, rosids, hamamelidids, monocots, and ginger. Earliest examples of ticks.
80 Ma: First ants.
68 Ma Tyrannosaurus, the largest terrestrial predator of North America appears in the fossil record. First species of Triceratops.
Cenozoic Era
65.5 Ma – present
65.5 Ma The Cretaceous–Tertiary extinction event eradicates about half of all animal species, including mosasaurs, pterosaurs, plesiosaurs, ammonites, belemnites, rudist and inoceramid bivalves, most planktic foraminifers, and all of the dinosaurs excluding their descendants the birds
63 Ma Evolution of the creodonts, an important group of carnivorous mammals.
60 Ma Diversification of large, flightless birds. Earliest true primates, along with the first semelid bivalves, edentates, carnivorous and lipotyphlan mammals, and owls. The ancestors of the carnivorous mammals (miacids) were alive.
55 Ma: Modern bird groups diversify (first song birds, parrots, loons, swifts, woodpeckers), first whale (Himalayacetus), earliest rodents, lagomorphs, armadillos, appearance of sirenians, proboscideans, perissodactyl and artiodactyl mammals in the fossil record. Angiosperms diversify. The ancestor (according to theory) of the species in Carcharodon, the early mako shark Isurus hastalis, is alive.
52 Ma First bats appear (Onychonycteris).
40 Ma: Modern-type butterflies and moths appear. Extinction of Gastornis. Basilosaurus, one of the first of the giant whales, appeared in the fossil record.
37 Ma: First Nimravid carnivores (“False Saber-toothed Cats”) - these species are unrelated to modern-type felines
35 Ma: Grasses evolve from among the angiosperms; grasslands begin to expand. Slight increase in diversity of cold-tolerant ostracods and foraminifers, along with major extinctions of gastropods, reptiles, and amphibians. Many modern mammal groups begin to appear: first glyptodonts, ground sloths, dogs, peccaries, and the first eagles and hawks. Diversity in toothed and baleen whales.
30 Ma First balanids and eucalypts, extinction of embrithopod and brontothere mammals, earliest pigs and cats.
28 Ma: Paraceratherium appears in the fossil record, the largest terrestrial mammal that ever lived.
25 Ma First deer.
20 Ma First giraffes and giant anteaters, increase in bird diversity.
15 Ma: Mammut appears in the fossil record, first bovids and kangaroos, diversity in Australian megafauna.
10 Ma Grasslands and savannas are established, diversity in insects, especially ants and termites, horses increase in body size and develop high-crowned teeth, major diversification in grassland mammals and snakes.
6.5 Ma First hominin (Sahelanthropus).
4.8 Ma Mammoths appear in the fossil record.
4 Ma Evolution of Australopithecus, Stupendemys appears in the fossil record as the largest freshwater turtle.
3 Ma The Great American Interchange, where various land and freshwater faunas migrated between North and South America. Armadillos, opossums, hummingbirds, and vampire bats traveled to North America while horses, tapirs, saber-toothed cats, and deer entered South America. The first short-faced bears (Arctodus) appear.
2 Ma: First members of the genus Homo appear in the fossil record. Diversification of conifers in high latitudes. The eventual ancestor of cattle, Bos primigenius evolves in India
350 ka Evolution of Neanderthals
200 ka: Anatomically modern humans appear in Africa.[40][41][42] Around 50,000 years before present they start colonising the other continents, replacing the Neanderthals in Europe and other hominins in Asia.
30 ka Extinction of Neanderthals
4500 ya The last members of a dwarf race of Woolly Mammoths vanish from Wrangel Island near Alaska
384 ya (1627) The last recorded wild Aurochs die out
75 ya (1936) The Thylacine goes extinct in a Tasmanian zoo, the last member of the family Thylacinidae
See also
Evolutionary history of life
Evolutionary history of plants
Extinction events
Geologic time scale
History of Earth
Natural history
Sociocultural evolution
Timeline of human evolution
Timeline of plant evolution
Further reading
The Ancestor’s Tale by Richard Dawkins, for a list of ancestors common to humans and other living species](http://i.imgur.com/xAFVQ.jpg)
If the Life of the Earth was reduced to a 24 hour clock
The age of the Earth is 4.54 billion years (4.54 × 109 years ± 1%).[1][2][3] This age is based on evidence from radiometric age dating of meteorite material and is consistent with the ages of the oldest-known terrestrial and lunar samples. Following the scientific revolution and the development of radiometric age dating, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old.[4]
The oldest such minerals analyzed to date – small crystals of zircon from the Jack Hills of Western Australia – are at least 4.404 billion years old.[5][6][7] Comparing the mass and luminosity of the Sun to the multitudes of other stars, it appears that the solar system cannot be much older than those rocks. Ca-Al-rich inclusions (inclusions rich in calcium and aluminium) – the oldest known solid constituents within meteorites that are formed within the solar system – are 4.567 billion years old,[8][9] giving an age for the solar system and an upper limit for the age of Earth.
It is hypothesised that the accretion of Earth began soon after the formation of the Ca-Al-rich inclusions and the meteorites. Because the exact accretion time of Earth is not yet known, and the predictions from different accretion models range from a few millions up to about 100 million years, the exact age of Earth is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages.
—
Main article: Timeline of evolution
- Current models in the origin of life
- Origin of organic molecules
- “Soup” theory today: Miller’s experiment and subsequent work
- The deep sea vent theory
- Fox’s experiments
- Eigen’s hypothesis
- Hoffmann’s contributions
- Wächtershäuser’s hypothesis
- Radioactive beach hypothesis
- Thermodynamic origin of life: ultraviolet and temperature-assisted replication (UVTAR) model
- Models to explain homochirality
- Self-organization and replication
- From organic molecules to protocells
- Other models
Morse and MacKenzie have suggested that oceans may have appeared first in the Hadean eon, as soon as two hundred million years (200 Ma) after the Earth was formed, in a hot 100 °C (212 °F) reducing environment, and that the pH of about 5.8 rose rapidly towards neutral.[23] This has been supported by Wilde[3] who has pushed the date of the zircon crystals found in the metamorphosed quartzite of Mount Narryer in Western Australia, previously thought to be 4.1–4.2 Ga, to 4.404 Ga. This means that oceans and continental crust existed within 150 Ma of Earth’s formation.
Despite this, the Hadean environment was one highly hazardous to life. Frequent collisions with large objects, up to 500 kilometres (310 mi) in diameter, would have been sufficient to vaporise the ocean within a few months of impact, with hot steam mixed with rock vapour leading to high altitude clouds completely covering the planet. After a few months the height of these clouds would have begun to decrease but the cloud base would still have been elevated for about the next thousand years. After that, it would have begun to rain at low altitude. For another two thousand years rains would slowly have drawn down the height of the clouds, returning the oceans to their original depth only 3,000 years after the impact event.[24]
Between 3.8 and 4.1 Ga, changes in the orbits of the gaseous giant planets may have caused a late heavy bombardment that pockmarked the moon and other inner planets (Mercury, Mars, and presumably Earth and Venus). This would likely have sterilized the planet, had life appeared before that time.
By examining the time interval between such devastating environmental events, the time interval when life might first have come into existence can be found for different early environments. The study by Maher and Stevenson shows that if the deep marine hydrothermal setting provides a suitable site for the origin of life, abiogenesis could have happened as early as 4.0 to 4.2 Ga, whereas if it occurred at the surface of the earth abiogenesis could only have occurred between 3.7 and 4.0 Ga.
This timeline of the evolution of life outlines the major events in the development of life on the planet Earth (See Organism). For a thorough explanatory context, see the history of Earth, and geologic time scale. The dates given in this article are estimates based on scientific evidence.
The basic timeline is a 4.5 billion year old Earth, with (very approximate) dates:
- 3.8 billion years of simple cells (prokaryotes),
- 3 billion years of photosynthesis,
- 2 billion years of complex cells (eukaryotes),
- 1 billion years of multicellular life,
- 600 million years of simple animals,
- 570 million years of arthropods (ancestors of insects, arachnids and crustaceans),
- 550 million years of complex animals,
- 500 million years of fish and proto-amphibians,
- 475 million years of land plants,
- 400 million years of insects and seeds,
- 360 million years of amphibians,
- 300 million years of reptiles,
- 200 million years of mammals,
- 150 million years of birds,
- 130 million years of flowers,
- 65 million years since the non-avian dinosaurs died out,
- 2.5 million years since the appearance of the genus Homo,
- 200,000 years since humans started looking like they do today,
- 25,000 years since Neanderthals died out.
Detailed timeline
- Ma, (“megaannum”) means “million years ago”. ka means “thousand years ago” and ya means “years ago”
Hadean Eon
3800 Ma and earlier.
4600 Ma: The planet Earth forms from the accretion disc revolving around the young Sun.
Between 4500 and 3500 Ma: The earliest life appears, possibly derived from self-reproducing RNA molecules.[5][6] The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition, with natural selection favouring those molecules which are more efficient at replication. DNA molecules then take over as the main replicators and these archaic genomes soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: proto-cells.
3900 Ma Late Heavy Bombardment: peak rate of impact events upon the inner planets by meteoroids. This constant disturbance may have obliterated any life that had evolved to that point, or possibly not, as some early microbes could have survived in hydrothermal vents below the Earth’s surface;[10] or life might have been transported to Earth by a meteoroid.
Somewhere between 3900 and 2500 Ma Cells resembling prokaryotes appear.[12] These first organisms are chemoautotrophs: they use carbon dioxide as a carbon source and oxidize inorganic materials to extract energy. Later, prokaryotes evolve glycolysis, a set of chemical reactions that free the energy of organic molecules such as glucose and store it in the chemical bonds of ATP. Glycolysis (and ATP) continue to be used in almost all organisms, unchanged, to this day.
Archean Eon
3800 Ma – 2500 Ma
3500 Ma: Lifetime of the last universal ancestor; the split between bacteria and archaea occurs.
Bacteria develop primitive forms of photosynthesis which at first do not produce oxygen. These organisms generate ATP by exploiting a proton gradient, a mechanism still used in virtually all organisms.
3000 Ma: Photosynthesizing cyanobacteria evolve; they use water as a reducing agent, thereby producing oxygen as waste product. More recent research[citation needed], however, suggests a later time of 2700 Ma. The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The oxygen concentration in the atmosphere slowly rises, acting as a poison for many bacteria. The Moon is still very close to Earth and causes tides 1,000 feet (305 m) high. The Earth is continually wracked by hurricane-force winds. These extreme mixing influences are thought to stimulate evolutionary processes. (See Oxygen catastrophe)
Proterozoic Eon
2500 Ma – 542 Ma
By 1850 Ma Eukaryotic cells appear
By 1200 Ma Sexual reproduction first appears, increasing the rate of evolution.
1200 Ma: Simple multicellular organisms evolve, mostly consisting of cell colonies of limited complexity. First multicellular red algae evolve
850–630 Ma: A global glaciation may have occurred. Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution.
580–500 Ma: Most modern phyla of animals begin to appear in the fossil record during the Cambrian explosion. (A preserved specimen is called a “fossil” if it is older than some minimum age, most often the arbitrary date of 10,000 years ago. Hence, fossils range in age from the youngest at the start of the Holocene Epoch to the oldest from the Archaean Eon, up to 3.4 billion years old.)
580–540 Ma: The accumulation of atmospheric oxygen allows the formation of an ozone layer. This blocks ultraviolet radiation, permitting the colonisation of the land.
560 Ma Earliest fungi
550 Ma First fossil evidence for ctenophora (comb-jellies), porifera (sponges), and anthozoa (corals & anemones)
Phanerozoic Eon
542 Ma – present
The Phanerozoic Eon, literally the “period of well-displayed life”, marks the appearance in the fossil record of abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, which are divided by major mass extinctions.
Paleozoic Era
542 Ma – 251.0 Ma
535 Ma Major diversification of living things in the oceans: chordates, arthropods (e.g. trilobites, crustaceans), echinoderms, mollusks, brachiopods, foraminifers and radiolarians, etc.
530 Ma The first known footprints on land date to 530 Ma, indicating that early animal explorations may have predated the development of terrestrial plants.
485 Ma First vertebrates with true bones (jawless fishes).
450 Ma Land arthropod burrows (millipedes) appear, along with the first complete conodonts and echinoids.
434 Ma The first primitive plants move onto land,[33] having evolved from green algae living along the edges of lakes.[34] They are accompanied by fungi[citation needed], which may have aided the colonization of land through symbiosis.
420 Ma Earliest ray-finned fishes, trigonotarbid arachnids, and land scorpions.
363 Ma By the start of the Carboniferous Period, the Earth begins to be recognisable. Insects roamed the land and would soon take to the skies; sharks swam the oceans as top predators, and vegetation covered the land, with seed-bearing plants and forests soon to flourish.
Four-limbed tetrapods gradually gain adaptations which will help them occupy a terrestrial life-habit.
320 Ma Synapsids separate from sauropsids (reptiles) in late Carboniferous
280 Ma Earliest beetles, seed plants and conifers diversify while lepidodendrids and sphenopsids decrease. Terrestrial temnospondyl amphibians and pelycosaurs (e.g. Dimetrodon) diversify in species.
251.4 Ma The Permian-Triassic extinction event eliminates over 90-95% of marine species. Terrestrial organisms were not as seriously affected as the marine biota. This “clearing of the slate” may have led to an ensuing diversification, but life on land took 30M years to completely recover.
Mesozoic Era
From 251.4 Ma The Mesozoic Marine Revolution begins: increasingly well-adapted and diverse predators pressurise sessile marine groups; the “balance of power” in the oceans shifts dramatically as some groups of prey adapt more rapidly and effectively than others.
245 Ma Earliest ichthyosaurs.
225 Ma Earliest dinosaurs (prosauropods), first cardiid bivalves, diversity in cycads, bennettitaleans, and conifers. First teleost fishes.
220 Ma Gymnosperm forests dominate the land; herbivores grow to huge sizes in order to accommodate the large guts necessary to digest the nutrient-poor plants.[citation needed], first flies and turtles (Odontochelys). First Coelophysoid dinosaurs
215 Ma: First mammals (e.g. Eozostrodon), minor vertebrate extinctions occur
200 Ma: The first accepted evidence for viruses (at least, the group Geminiviridae) exists. Viruses are still poorly understood and may have arisen before “life” itself, or may be a more recent phenomenon.
Major extinctions in terrestrial vertebrates and large amphibians. Earliest examples of Ankylosaurian dinosaurs
155 Ma First blood-sucking insects (ceratopogonids), rudist bivalves, and cheilosome bryozoans. Archaeopteryx, a possible ancestor to the birds, appears in the fossil record, along with triconodontid and symmetrodont mammals. Diversity in stegosaurian and theropod dinosaurs.
130 Ma: The rise of the Angiosperms: These flowering plants boast structures that attract insects and other animals to spread pollen. This innovation causes a major burst of animal evolution through co-evolution. First freshwater pelomedusid turtles.
100 Ma Earliest bees.
90 Ma Extinction of ichthyosaurs. Earliest snakes and nuculanid bivalves. Large diversification in angiosperms: magnoliids, rosids, hamamelidids, monocots, and ginger. Earliest examples of ticks.
80 Ma: First ants.
68 Ma Tyrannosaurus, the largest terrestrial predator of North America appears in the fossil record. First species of Triceratops.
Cenozoic Era
65.5 Ma – present
65.5 Ma The Cretaceous–Tertiary extinction event eradicates about half of all animal species, including mosasaurs, pterosaurs, plesiosaurs, ammonites, belemnites, rudist and inoceramid bivalves, most planktic foraminifers, and all of the dinosaurs excluding their descendants the birds
63 Ma Evolution of the creodonts, an important group of carnivorous mammals.
60 Ma Diversification of large, flightless birds. Earliest true primates, along with the first semelid bivalves, edentates, carnivorous and lipotyphlan mammals, and owls. The ancestors of the carnivorous mammals (miacids) were alive.
55 Ma: Modern bird groups diversify (first song birds, parrots, loons, swifts, woodpeckers), first whale (Himalayacetus), earliest rodents, lagomorphs, armadillos, appearance of sirenians, proboscideans, perissodactyl and artiodactyl mammals in the fossil record. Angiosperms diversify. The ancestor (according to theory) of the species in Carcharodon, the early mako shark Isurus hastalis, is alive.
52 Ma First bats appear (Onychonycteris).
40 Ma: Modern-type butterflies and moths appear. Extinction of Gastornis. Basilosaurus, one of the first of the giant whales, appeared in the fossil record.
37 Ma: First Nimravid carnivores (“False Saber-toothed Cats”) - these species are unrelated to modern-type felines
35 Ma: Grasses evolve from among the angiosperms; grasslands begin to expand. Slight increase in diversity of cold-tolerant ostracods and foraminifers, along with major extinctions of gastropods, reptiles, and amphibians. Many modern mammal groups begin to appear: first glyptodonts, ground sloths, dogs, peccaries, and the first eagles and hawks. Diversity in toothed and baleen whales.
30 Ma First balanids and eucalypts, extinction of embrithopod and brontothere mammals, earliest pigs and cats.
28 Ma: Paraceratherium appears in the fossil record, the largest terrestrial mammal that ever lived.
25 Ma First deer.
20 Ma First giraffes and giant anteaters, increase in bird diversity.
15 Ma: Mammut appears in the fossil record, first bovids and kangaroos, diversity in Australian megafauna.
10 Ma Grasslands and savannas are established, diversity in insects, especially ants and termites, horses increase in body size and develop high-crowned teeth, major diversification in grassland mammals and snakes.
6.5 Ma First hominin (Sahelanthropus).
4.8 Ma Mammoths appear in the fossil record.
4 Ma Evolution of Australopithecus, Stupendemys appears in the fossil record as the largest freshwater turtle.
3 Ma The Great American Interchange, where various land and freshwater faunas migrated between North and South America. Armadillos, opossums, hummingbirds, and vampire bats traveled to North America while horses, tapirs, saber-toothed cats, and deer entered South America. The first short-faced bears (Arctodus) appear.
2 Ma: First members of the genus Homo appear in the fossil record. Diversification of conifers in high latitudes. The eventual ancestor of cattle, Bos primigenius evolves in India
350 ka Evolution of Neanderthals
200 ka: Anatomically modern humans appear in Africa.[40][41][42] Around 50,000 years before present they start colonising the other continents, replacing the Neanderthals in Europe and other hominins in Asia.
30 ka Extinction of Neanderthals
4500 ya The last members of a dwarf race of Woolly Mammoths vanish from Wrangel Island near Alaska
384 ya (1627) The last recorded wild Aurochs die out
75 ya (1936) The Thylacine goes extinct in a Tasmanian zoo, the last member of the family Thylacinidae
See also
- Evolutionary history of life
- Evolutionary history of plants
- Extinction events
- Geologic time scale
- History of Earth
- Natural history
- Sociocultural evolution
- Timeline of human evolution
- Timeline of plant evolution
Further reading
- The Ancestor’s Tale by Richard Dawkins, for a list of ancestors common to humans and other living species
