What is the general timeline for life on earth?

1 Answer
Apr 11, 2016

Life may have started as far back as 3.8 billion years.

Explanation:

General milestones in life's development:

4.0 billion years - organic molecules capable of forming life were around, but not yet formed into cells.

3.8 billion years - first pre-cells form from organic molecule building block start to form
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3.7 billion years. - first prokaryotic bacteria evolve.

3 billion years - first reef building photosynthetic prokaryotic bacteria evolve and start pumping oxygen into the oceans.

2.5 billion year - oxygen from photosynthesis starts to build up in the atmosphere. This changes the course of evolution to favour organisms that can use oxygen in metabolism.

1.5 billion years - Eukaryotic cells (like the kind we are made of) with a distinct nucleus evolve.

700 million year - multicellular eukaryotic cells start to form simple soft-bodied animals, like worms.

550 million years - hard shell invertebrates evolve as does predation.

500 million years - first vertebrates evolve - sharks around 400 million years.

400 million years - land plants, amphibians and insects populate the land

350 million years - first sharks reproduce by sexual intercourse.

250 million years - major mass extinction event wipes out 90% of species on Earth.

200 million years - first reptiles evolve. First mammal-like reptiles evolve shortly thereafter - our distant ancestors.

150 million years - dinosaurs rule for over 100 million years, and die out 65 million years ago. They are wiped out by a giant asteroid.

65 million years ago - mammals take over the ecological niches that dinos previously occupied.

40 million years ago - first primates (our ancestors) evolve

2 million years ago - our homo sapient lineage evolves, but we are not the pinnacle of evolution!

last 10,000 years - humans start to radically change the planet in many not so great ways