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The Hadean eon represents the time before a reliable (fossil) record of life; it began with the formation of the planet and ended 4.0 billion years ago. The following Archean and Proterozoic eons produced the beginnings of life on Earth and its earliest evolution .
Many modern mammal groups begin to appear: first glyptodonts, ground sloths, canids, peccaries, and the first eagles and hawks. Diversity in toothed and baleen whales. 33 Ma Evolution of the thylacinid marsupials . 30 Ma First balanids and eucalypts, extinction of embrithopod and brontothere mammals, earliest pigs and cats. 28 Ma
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
Human history is the record of humankind from prehistory to the present. Modern humans evolved in Africa around 300,000 years ago and initially lived as hunter-gatherers.They migrated out of Africa during the Last Ice Age and had spread across Earth's continental land except Antarctica by the end of the Ice Age 12,000 years ago.
A creation myth or cosmogonic myth is a type of cosmogony, [2] a symbolic narrative of how the world began and how people first came to inhabit it. [3] [4] [5] While in popular usage the term myth often refers to false or fanciful stories, members of cultures often ascribe varying degrees of truth to their creation myths.
An early stem-primate, Plesiadapis, still had claws and eyes on the side of the head, making it faster on the ground than in the trees, but it began to spend long times on lower branches, feeding on fruits and leaves. The Plesiadapiformes very likely contain the ancestor species of all primates. [24]
In other models, reheating is often considered to mark the start of the electroweak epoch, and some theories, such as warm inflation, avoid a reheating phase entirely. After inflation ended, the universe continued to expand, but at a decelerating rate. About 4 billion years ago the expansion gradually began to speed up again.
These elements gradually accreted and began orbiting in disks of gas and dust. Gravitational accretion of material at the hot and dense centers of these protoplanetary disks formed stars by the fusion of hydrogen. [51] Early stars were massive and short-lived, producing all the heavier elements through stellar nucleosynthesis.