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4600 BCE
Formation Of Earth And Moon
The giant-impact hypothesis, sometimes called the Big Splash, or the Theia Impact suggests that the Moon formed out of the debris left over from a collision between Earth and an astronomical body the size of Mars, approximately 4.5 billion years ago, in the Hadean eon -
Period: 4600 BCE to 550 BCE
Precambrian Time
The Precambrian Era comprises all of geologic time prior to 600 million years ago. It is now known that life on Earth began by the early Archean and that fossilized organisms became more and more abundant throughout Precambrian time. -
3500 BCE
Prokaryotes (bacteria)
A microscopic single-celled organism that has neither a distinct nucleus with a membrane nor other specialized organelles. Prokaryotes include the bacteria and cyanobacteria. -
2400 BCE
Significant Rise In Oxygen, To ~2% Level
Cyanobacteria or blue-green algae became the first microbes to produce oxygen by photosynthesis, perhaps as long ago as 3.5 billion years ago and certainly by 2.7 billion years ago. But, mysteriously, there was a long lag time – hundreds of millions of years – before Earth’s atmosphere first gained significant amounts oxygen, some 2.4 billion to 2.3 billion years ago. -
1800 BCE
First Eukaryotes
Eukaryotes are organisms with a nucleus. The oldest evidence of eukaryotes is from 2.7 billion years ago. Scientists believe that a nucleus and other organelles inside a eukaryotic cell formed when one prokaryotic organism engulfed another, which then lived inside and contributed to the functioning of its host. -
550 BCE
Jellyfish
The first animals known to swim using muscles instead of drifting with the whims of the waves. The oldest ancestors of modern day jellies lived at least 500 million years ago, and maybe as long as 700 million years ago.
