Basic timeline of Evolution - St. Joseph Academy
Basic timeline of Evolution
In its 4.6 billion years circling the sun, the Earth has harbored an increasing diversity of life forms:
• Universe (Big Bang occurred) 13.7 billion years ago
• Earth approx. 4.6 billion years old
• for the last 3.8 billion years, simple cells (prokaryotes);
• for the last 3.4 billion years, cyanobacteria performing photosynthesis;
• for the last 2 billion years, complex cells (eukaryotes);
• for the last 1 billion years, multicellular life;
• for the last 600 million years, simple animals;
• for the last 550 million years, bilaterians, animals with a front and a back;
• for the last 500 million years, fish and proto-amphibians;
• for the last 475 million years, land plants;
• for the last 400 million years, insects and seeds;
• for the last 360 million years, amphibians;
• for the last 300 million years, reptiles;
• for the last 200 million years, mammals;
• for the last 150 million years, birds;
• for the last 130 million years, flowers;
• for the last 60 million years, the primates,
• for the last 20 million years, the family Hominidae (great apes);
• for the last 2.5 million years, the genus Homo (human predecessors);
• for the last 200,000 years, anatomically modern humans.
Periodic extinctions have temporarily reduced diversity, eliminating:
• 2.4 billion years ago, many obligate anaerobes, in the oxygen catastrophe;
• 252 million years ago, the trilobites, in the Permian–Triassic extinction event;
• 66 million years ago, the pterosaurs and nonavian dinosaurs, in the Cretaceous–Paleogene extinction event.
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