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4.5 BYA - EARTH FORMED
Planet's surface cooled and formed a rocky crust. Water vapor in the atmosphere condensed to form vast oceans. -
3.8 BYA - PROKARYOTES
It is generally accepted that the first living cells were some form of prokaryote and may have developed out of protobionts. Fossilized prokaryotes approximately 3.5 billion years old have been discovered (less than 1 billion years after the formation of the earth’s crust), and prokaryotes are perhaps the most successful and abundant organism even today. -
3.4 BYA - STROMATOLITES
A variety of stromatolite morphologies exist including conical, stratiform, branching, domal, and columnar types. Stromatolites occur widely in the fossil record of the Precambrian, but are rare today. Very few ancient stromatolites contain fossilized microbes. -
2 BYA - EUKARYOTES
Eukaryotic cells are typically much larger than those of prokaryotes. They have a variety of internal membranes and structures, called organelles, and a cytoskeleton composed of microtubules, microfilaments, and intermediate filaments, which play an important role in defining the cell's organization and shape. -
1 BYA - MULTICELLULAR LIFE
Multicellularity has evolved independently dozens of times in the history of Earth, for example in plants and animals. Multicellularity exists in both prokaryotes and eukaryotes, and first appeared several billion years ago in cyanobacteria. Most life that can be seen with the naked eye is multicellular, as are all animals and land plants. -
600 MYA - SIMPLE ANIMALS
Animals are eukaryotic and mostly multicellular, which separates them from bacteria and most protists. They are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae.They are also distinguished from plants, algae, and fungi by lacking rigid cell walls. All animals are motile,[8] if only at certain life stages. In most animals, embryos pass through a blastula stage, which is a characteristic exclusive to animals. -
570 MYA - ARTHOPODS
An arthropod is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and jointed appendages. Arthropods are characterized by their jointed limbs and cuticles, which are mainly made of α-chitin; the cuticles of crustaceans are also biomineralized with calcium carbonate. -
550 MYA - COMPLEX ANIMALS
Multicellular life forms with a number of organs inside. Paleontologists now have fossil evidence these life forms first appeared about 600 million years ago. -
550 MYA - FISH
The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators. The first fish with jaws appeared in the Siluria -
475 MYA - LAND PLANTS
They are believed to have evolved from within a group of complex green algae during the Paleozoic era (which started around 540 million years ago). The Charales or stoneworts appear to be the best living illustration of that developmental step. -
400 MYA - INSECTS AND SEEDS
Insects are among the most diverse groups of animals on the planet, including more than a million described species and representing more than half of all known living organisms. Insects may be found in nearly all environments, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans. The origin of seed plants is a problem that still remains unsolved. However, more and more data tends to place this origin in the middle Devonian. -
360 MYA - AMPHIBIANS
Amphibians are members of the class Amphibia, a group of vertebrates whose living forms include frogs, toads, salamanders, newts and caecilians. They are characterized as non-amniote, ectothermic tetrapods, meaning their eggs are not surrounded by membranes, they are cold-blooded, and they have four limbs. The earliest amphibians evolved in the Devonian Period from Sarcopterygians, fish that had lungs and bony fins, features that were helpful in adapting to dry land. -
300 MYA - REPTILES
Reptiles are members of a class of air-breathing, ectothermic (cold-blooded) vertebrates which are characterized by skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors. Modern reptiles inhabit every continent with the exception of Antarctica. Reptiles originated around 320-310 million years ago during the Carboniferous period. -
200 MYA - MAMMALS
Air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young. The early synapsid mammalian ancestors were sphenacodont pelycosaurs, a group that also included Dimetrodon. At the end of the Carboniferous period, this group diverged from the sauropsid line that led to today's reptiles and birds. -
150 MYA - BIRDS
The fossil record indicates that birds emerged within theropod dinosaurs during the Jurassic period, around 160 million years (Ma) ago. Paleontologists regard birds as the only clade of dinosaurs to have survived the Cretaceous–Paleogene extinction event 65.5 Ma ago. -
130 MYA - FLOWERS
While land plants have existed for about 425 million years, the first ones reproduced by a simple adaptation of their aquatic counterparts: spores. In the sea, plants—and some animals—can simply scatter out genetic clones of themselves to float away and grow elsewhere. This is how early plants reproduced. But plants soon evolved methods of protecting these copies to deal with drying out and other abuse which is even more likely on land than in the sea. -
65 MYA - DINOSAURS DIED OUT
The Cretaceous–Paleogene extinction event, often referred to as the Cretaceous–Tertiary extinction event, occurred approximately 65.5 million years ago (Ma) at the end of the Maastrichtian age of the Cretaceous period. It was a large-scale mass extinction of animal and plant species in a geologically short period of time. -
2.5 MYA - HOMO SAPIEN
The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine ancestors with the appearance of Homo habilis. All species of the genus except Homo sapiens (modern humans) are extinct. Homo neanderthalensis, traditionally considered the last surviving relative, died out about 24,000 years ago, though a recent discovery suggests that another species, Homo floresiensis, discovered in 2003, may have lived as recently as 12,000 years ago. -
200,000 - MODERN HUMANS
Scientific study of human evolution is concerned, primarily, with the development of the genus Homo, but usually involves studying other hominids and hominines as well, such as Australopithecus. "Modern humans" are defined as the Homo sapiens species, of which the only extant subspecies is known as Homo sapiens sapiens.
