Scientists have estimated that over the course of Earth's history, anywhere between 1 and 4 billion species have existed on this planet.
How many species have existed on earth?
How many years since the universe's beginning? The Earth's ?
Earth began to form over
4.6 billion years ago
Toward the end of the
Archean Period and at the beginning of the
Proterozoic Period, about 2.5 billion years ago, oxygen-forming photosynthesis began to occur. The first fossils were a type of
blue-green algae that could photosynthesize.
Compared to prokaryotic organisms such as bacteria, plants and animals have a relatively recent evolutionary origin. DNA evidence suggests that the first eukaryotes evolved from prokaryotes, between 2500 and
1000 million years ago.
Eozostrodon was one of the first true mammals; it lived during the late Triassic period and early Jurassic period, about
210 million years ago. This small, primitive, egg-laying mammal fed the young with mother's milk.
Most animal species flourished and became extinct long before the first monkeys and their prosimian ancestors evolved. While the earth is about 4.54 billion years old and the first life dates to at least
3.5 billion years ago, the first primates did not appear until around
50-55 million years ago.
How many small blind steps would it take to make a human, in your opinion?