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Evolutionary Timeline
Author: Javid Zafar Qureshi
Time
(Myr ago) Event
4600 Formation of the approximately homogeneous solid Earth by planetesimal accretion
4300 Melting of the Earth due to radioactive and gravitational heating which leads to its differentiated interior structure as well as outgassing of molecules such as water, methane, ammonia, hydrogen, nitrogen, and carbon dioxide
4300 Atmospheric water is photodissociated by ultraviolet light to give oxygen atoms which are incorporated into an ozone layer and hydrogen molecules which escape into space
4000 Bombardment of the Earth by planetesimals stops
3800 The Earth's crust solidifies--formation of the oldest rocks found on Earth
3800 Condensation of atmospheric water into oceans
3500-2800 Prokaryotic cell organisms develop
3500-2800 Beginning of photosynthesis by blue-green algae which releases oxygen molecules into the atmosphere and steadily works to strengthen the ozone layer and change the Earth's chemically reducing atmosphere into a chemically oxidizing one
2400 Rise in the concentration of oxygen molecules stops the deposition of uraninites (since they are soluble when combined with oxygen) and starts the deposition of banded iron formations
2000 The Oklo natural fission reactor in Gabon goes into operation
1600 The last reserves of reduced iron are used up by the increasing atmospheric oxygen--last banded iron formations
1500 Eukaryotic cell organisms develop
1500-600 Rise of multicellular organisms
580-545 Fossils of Ediacaran organisms are made
545 Cambrian explosion of hard-bodied organisms
528-526 Fossilization of the Chengjiang site
517-515 Fossilization of the Burgess Shale
500-450 Rise of the fish--first vertebrates
430 Waxy coated algae begin to live on land
420 Millipedes have evolved--first land animals
375 The Appalachian mountains are formed via a plate tectonic collision between North America, Africa, and Europe
375 Appearance of primitive sharks
350-300 Rise of the amphibians
350 Primitive insects have evolved
350 Primitive ferns evolve--first plants with roots
300-200 Rise of the reptiles
300 Winged insects have evolved
280 Beetles and weevils have evolved
250 Permian period mass extinction
230 Roaches and termites have evolved
225 Modern ferns have evolved
225 Bees have evolved
200 Pangaea starts to break apart
200 Primitive crocodiles have evolved
200 Appearance of mammals
145 Archaeopteryx walks the Earth
136 Primitive kangaroos have evolved
100 Primitive cranes have evolved
90 Modern sharks have evolved
65 K-T Boundary--extinction of the dinosaurs and beginning
of the reign of mammals
60 Rats, mice, and squirrels have evolved
60 Herons and storks have evolved
55 Rabbits and hares have evolved
50 Primitive monkeys have evolved
28 Koalas have evolved
20 Parrots and pigeons have evolved
20-12 The chimpanzee and hominid lines evolve
10-4 Ramapithecus exist
4 Development of hominid bipedalism
4-1 Australopithecus exist
3.5 The Australopithecus Lucy walks the Earth
2 Widespread use of stone tools
2-0.01 Most recent ice age
1.6-0.2 Homo erectus exist
1-0.5 Homo erectus tames fire
0.3 Geminga supernova explosion at a distance of roughly 60
pc--roughly as bright as the Moon
0.2-0.03 Homo sapiens neanderthalensis exist
0.05-0 Homo sapiens sapiens exist
0.04-0.012 Homo sapiens sapiens enter Australia from
southeastern Asia and North America from northeastern Asia
0.025-0.01 Most recent glaciation--an ice sheet covers much of the northern United States
0.02 Homo sapiens sapiens paint the Altamira Cave
0.012 Homo sapiens sapiens have domesticated dogs in Kirkuk,
Iraq
0.01 First permanent Homo sapiens sapiens settlements
0.01 Homo sapiens sapiens learn to use fire to cast copper and harden pottery
0.006 Writing is developed in Sumeria
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