What is the general timeline for life on earth?
1 Answer
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
.
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
