Part 8: Explosive

Part 7 <-8-> Part 9

Next up, after the almost 4billion years of waiting, exactly almost 850mya, earth was filled with Oxygen. A shy 300million years later, came the Cambrian explosion.

Here is a nice timescale graph from Wikipedia:

The Cambrian explosion (also known as Cambrian radiation[1] or Cambrian diversification) is an interval of time approximately 538.8?million years ago in the Cambrian period of the early Paleozoic when a sudden radiation of complex life occurred, and practically all major animal phyla started appearing in the fossil record.[2][3][4] It lasted for about 13[5][6][7] to 25[8][9] million years and resulted in the divergence of most modern metazoan phyla.[10] The event was accompanied by major diversification in other groups of organisms as well.[a]

We can also se in this timescale the various extinction events, which, while super interesting, will have to make for extracurricular reading, since in this story we're focusing on us, the survivors.

Extinction events or bottlenecks can somewhat be visualised by this experiment:

The Evolution of Bacteria on a “Mega-Plate” Petri Dish (Kishony Lab)

Above shows the experiment with increasing strengths of antibiotics delinieated from the sides to center

Above shows the first barrier (or "filter") where all of the bacteria initially come up against the first increases in antibiotic strength. Note that for a while, the bacteria is container behind the filter until singular bacteria incidentally mutate resistance to the antibiotic and continue to expand and grow towards the middle where the antibiotic is 1000 times stronger than at the start.

This then continues to happen at each filter stage, some time passes and untold amounts of mutuations happen both at the barrier, and away from. Imagine this as a filter for humans such as sea-faring: we are bound to land until one day we become smart enough to take to the seas and populate other areas. North Sentinel Island comes to mind.

What this shows us is that, given enough time, any organism and life form can and eventually will mutate some way past the filter and that then becomes part of the permanent DNA make-up of that life form. Or go extinct. let's call it 50/50. The new strains continue to thrive and further mutate outside of the traditional boundaries. Remember to take the entire course of antibiotics your doctor gives you, or you'll face the wrath of evolution! srsly tho don't skimp on that schedule.

Now on to the extinction events:

Here’s a summary of the major extinction events, sorted by year, along with the likely causes and information on what species died out and what survived during each interval:

1. End Ordovician (444 million years ago)

• Likely cause: Climate change due to a major ice age, followed by a warming period.
• What died out: Around 85% of marine species, including many trilobites, brachiopods, and graptolites.
• What survived: Some species of brachiopods, bivalves, and gastropods managed to survive.

2. Late Devonian (360 million years ago)

• Likely cause: Extended periods of marine anoxia (lack of oxygen in the water) and possibly large-scale volcanic eruptions.
• What died out: About 75% of species, including many reef-building corals and jawless fish.
• What survived: Early tetrapods (four-limbed vertebrates) and some species of fish.

3. End Permian (250 million years ago)

• Likely cause: Massive volcanic eruptions in Siberia, leading to global warming, ocean acidification, and a drop in ocean oxygen levels.
• What died out: The largest extinction event, wiping out around 96% of marine species and 70% of terrestrial vertebrate species. This included trilobites, many types of corals, and large amphibians.
• What survived: Some species of reptiles, amphibians, and small mammals.

4. End Triassic (200 million years ago)

• Likely cause: Intense volcanic activity associated with the breakup of Pangea, leading to increased carbon dioxide levels and ocean acidification.
• What died out: About 80% of species, including many large amphibians and early reptiles.
• What survived: Dinosaurs, which then became the dominant terrestrial vertebrates, and some species of fish and plants.

5. End Cretaceous (65 million years ago)

• Likely cause: The Chicxulub meteor impact in Yucatán, Mexico, possibly combined with volcanic eruptions and climate change.
• What died out: Around 75% of species, including all non-avian dinosaurs, many marine reptiles, and ammonites.
• What survived: Birds (avian dinosaurs), mammals, crocodiles, turtles, and some species of plants and fish.

As you can see it's been an "event"-ful couple of 100mil years. The amazing thing about this is that you, the person(or robot) reading this is: you are literally the most recent iteration in one continuous many-billion-year-process. You can literally trace your ancestry all the way back to that black hole we were spat out of. Going before that will be a little more challenging. There's another smaller, but even more significant one i'll cover in a later piece.

Each extinction event has been such a barrier for living creatures to adapt to and survive, and survive and adapt we did.