Timeline of evolution
You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.
- For the history of evolutionary biology, see History of evolutionary thought.
This timeline of the evolution of life outlines the major events in the development of life on the planet Earth. 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.
In biology, evolution is the process by which populations of organisms acquire and pass on novel traits from generation to generation. Its occurrence over large stretches of time explains the origin of new species and ultimately the vast diversity of the biological world. Contemporary species are related to each other through common descent, products of evolution and speciation over billions of years.
Basic timeline
Template:Include timeline The basic timeline is a 4.6 billion year old Earth, with (very approximately):
- 4 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,
- 200,000 years since humans started looking like they do today.
Detailed timeline
- Note that Ma means "million years ago".
Hadean eon
3800 Ma and earlier.
| Date | Event |
|---|---|
| 4567.17 Ma | The planet Earth forms from the accretion disc revolving around the young Sun. |
| 4533 Ma | The planet Earth and the planet Theia collide, sending countless moonlets into orbit around the young Earth. These moonlets eventually coalesce to form the Moon. The gravitational pull of the new Moon stabilises the Earth's fluctuating axis of rotation and sets up the conditions for the formation of life.[1] |
| 4100 Ma | The surface of the Earth cools enough for the crust to solidify. The atmosphere and the oceans form.[1]PAH infall, and Iron-Sulfide synthesis along deep ocean platelet boundaries, may have led to the RNA world of competing metabolising organic compounds.Template:CheckPOV |
| Between 4500 and 2500 Ma | The earliest life appears, possibly derived from self-reproducing RNA molecules. The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition. Natural selection favours those molecules which are more efficient at replication. DNA molecules then take over as the main replicators. They 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 meteors. This constant disturbance probably obliterated any life that had already evolved, as the oceans boiled away completely; conversely, life may have been transported to Earth by a meteor. [1] |
| Somewhere between 3900 - 2500 Ma | Cells resembling prokaryotes appear. 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. Glycolysis generates ATP molecules as short-term energy currency, and ATP continue to be used in almost all organisms, unchanged, to this day. |
Archean eon
3800 Ma - 2500 Ma
| Date | Event |
|---|---|
| 3500 Ma | Lifetime of the last universal ancestor; the split between the bacteria and the 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. The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The oxygen concentration in the atmosphere subsequently rises, acting as a poison for many bacteria. The moon is still very close to the earth and causes tides 1000 feet 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
| Date | Event |
|---|---|
| By 2100 Ma | Eukaryotic cells appear. Eukaryotes contain membrane-bound organelles with diverse functions, probably derived from prokaryotes englufing each other via phagocytosis. |
| By 1200 Ma | Sexual reproduction evolves, increasing the rate of evolution.[1] |
| 1200 Ma | Simple multicellular organisms evolve, mostly consisting of cell colonies of limited complexity. |
| 850–630 Ma | A global glaciation may have reduced the diversity of life. Opinion is divided on whether it increased or decreased the rate of evolution.[citation needed] |
| 580-542 Ma | The Ediacaran biota represent the first large, complex multicellular organisms - although their affinities remain a subject of debate. |
| 580–500 Ma | Most modern groups begin to appear in the fossil record during the Cambrian explosion. |
| Around 540 Ma | The accumulation of atmospheric oxygen allows the formation of an ozone layer. This blocks ultraviolet radiation, permitting the colonisation of the land. |
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
| Date | Event |
|---|---|
| 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.[1] |
| 475 Ma | The first primitive plants move onto land,[1][citation needed] having evolved from green algae living along the edges of lakes.[1] They are accompanied by fungi, which may have aided the colonisation of land through symbiosis. |
| 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 predated the oceans,[1] 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. |
| 251.4Ma | The Permian-Triassic extinction event eliminates over 95% of species. This "clearing of the slate" may have led to an ensuing diversification. |
Mesozoic era
| Date | Event |
|---|---|
| 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. |
| 220 Ma | Image:Eopraptor sketch5.png Eoraptor, an early dinosaur. 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] |
| 200 Ma | The first accepted evidence for viruses (at least, the group Geminiviridae) exists.[1] Viruses are still poorly understood and may have arisen before "life" itself, or may be a more recent phenomenon. |
| 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. |
Cenozoic era
65.5 Ma - present
| Date | Event |
|---|---|
| 65.5 Ma |
The Cretaceous–Tertiary extinction event eradicates about half of all animal species, including all non-avian dinosaurs. |
| 35 Ma | Grasses evolve from among the angiosperms; grassland dominates many terrestrial ecosystems. |
| 14,000 years ago | The term Anthropocene has been used to describe the period of time during which humans have had a major impact on the planet and its diversity of life. Its beginning is marked by the megafaunal extinction in the Americas which signify the onset of the Holocene extinction event. Fierce debate rages about the influence of man in the initiation of this extinction, but it is generally agreed that humanity is contributing somehow to its propagation, . |
| Present day | With a human population approaching 6.67 billion,[1] the impact of humanity is felt in all corners of the globe. Overfishing, anthropogenic climate change, industrialisation, intensive agriculture, clearance of rain forests and other activities contribute to a dramatically rising extinction rate.[1] If current rates continue, humanity will have seen the eradication of one-half of Earth's biodiversity over the next hundred years.[1] |
See also
- 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
References
External links
- History of the Earth from EvoWiki
- Berkeley Evolution
- Tree of Life Web Project - explore complete phylogenetic tree interactively
- A more compact timeline
- Palaeos - The Trace of Life on Earth
- University of Waikato - Sequence of Plant Evolution
- University of Waikato - Sequence of Animal Evolution
- Graphical Timeline of evolution
- EvoWiki's geologic timescale and timeline of evolution.
- History of Life on Earth
- Exploring Time from Planck Time to the lifespan of the universe
Basic topics in evolutionary biology | |
|---|---|
| Evidence of evolution | |
| Processes of evolution | adaptation · macroevolution · microevolution · speciation |
| Population genetic mechanisms | natural selection · genetic drift · gene flow · mutation |
| Evolutionary developmental biology (Evo-devo) concepts | phenotypic plasticity · canalisation · modularity |
| Modes of evolution | anagenesis · catagenesis · cladogenesis |
| History | History of evolutionary thought · Charles Darwin · The Origin of Species · modern evolutionary synthesis · Evolutionary history of life |
| Other subfields | ecological genetics · human evolution · molecular evolution · phylogenetics · systematics |
| List of evolutionary biology topics · Timeline of evolution | |
lt:Evoliucijos laiko skalė sh:Kronologija evolucije vi:Lịch trình tiến hóa của sự sống
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
