EarthHistory

Facts:

• Heavy bombardment from asteroids and comets
• Another planet, Theia, smashes into Earth, merging with it, but blasting away Earth's existing surface, casting off enough material to form our moon.
• Late Heavy Bombardment 4 to 3.8 billion years ago

Links: Palæos Wikipedia

Facts:

• The continents form.
• The first single-celled life appears in the primeval seas.
• The ancestor of all living things on Earth today lived 3.5 billion years ago.

Links: Palæos

Facts:

• Oxygen Catastrophe

Links: Palæos

Facts:

• The supercontinent Rodinia forms.
• Stromatolites (huge colonies of bacteria) dominate.
• Sexual reproduction evolves around 1.2 billion years ago.
• Ectasian period: 1400 to 1200 MYA. Evidence of red algae in 1200 MYA rock points to multicellular life appearing around this time.

Links: Palæos

Facts:

• [Check this. This is NPR's note for the whole Proterozoic.] Multicellular organisms such as algae develop. Soft-bodied animals follow hundreds of millions of years later.
• Earth's most severe ice age began 750 MYA and ended 580 MYA.
• Sponges, the world's first multicellular animals, evolve from cell colonies on or after 600 MYA.
• The ozone layer forms, making it possible for life to live on land without being harmed by UV radiation.

Links: Palæos

Facts:

• Some give the Cambrian as 544 to 505 MYA.
• Creatures with eyes appear about 540 MYA, sparking an evolutionary arms race. (Alternative scenario: Earth experienced tectonic plate movements much faster than normal, causing climate changes drastic enough to put evolution into overdrive.)
• Marine invertebrates, such as trilobites, dominate.
• The anomalocarid is Earth's top predator.
• Period ends with extinction events.

Links: Palæos

Facts:

• Some give the Ordovician as 505 to 440 MYA.
• The first vertebrates (such as primitive jawless fish) form.
• Period ends with extinction events.

Links: Palæos

Facts:

• Some give the Silurian as 440 to 410 MYA.
• Fresh-water fish and the first fish with jaws appear.
• Animals and plants make the move to land.

Links: Palæos

Facts:

• Some give the Devonian as 410 to 360 MYA.
• The first forests and land-dwelling vertebrates form.
• Species include: Dunkleosteus (armored fish)
• Period ends with a multi-million-year series of extinctions that killed off about 70% of all species.

Links: Palæos

Facts:

• Some mark this period as two: the Mississippian (360 to 325 MYA) and the Pennsylvanian (325 to 286 MYA).
• During the Mississippian, coal deposits begin, and sharks and large primitive trees develop.
• During the Pennsylvanian, the first reptiles appear, and insects and fern forests spread.

Links: Palæos

Facts:

• Some give the Permian as 286 to 245 MYA.
• Period ends with the largest mass extinction ever recorded: the reign of mammal-like reptiles ends, and most marine invertebrates die off.

Links: Palæos

Facts:

• Some give the Triassic as 245 to 208 MYA.
• Period ends with an extinction event.

Links: Palæos

Facts:

• Some give the Jurassic as 208 to 146 MYA.
• The first (true) mammals appear around 200 MYA, and the first birds take to the sky.

Links: Palæos

Facts:

• Flowering plants appear.
• Eomaia scansoria, earliest known ancestor of placental mammals, appears* (about 125 MYA).
• Period ends with the extinction of the dinosaurs (thought to have been triggered by a massive comet crashing into the Gulf of Mexico).

Links: Palæos Wikipedia

Links: Palæos Wikipedia

Facts:

• The first primates evolve around 55 MYA.

Links: Palæos Wikipedia

Links: Palæos Wikipedia

Links: Palæos Wikipedia

Links: Palæos Wikipedia

Facts:

• Modern humans (Homo sapiens) appear around 200,000 years ago.

Links: Palæos Wikipedia

Links: Palæos Wikipedia