Privileged Planet: life transformed early Earth (Introduction)

by David Turell , Monday, January 16, 2023, 18:22 (678 days ago) @ David Turell

I have constantly made the point the Earth evolved from a barren rocky beginning to arrive at a point humans could be supported:

https://aeon.co/essays/we-will-never-be-able-to-live-on-another-planet-heres-why?utm_so...

" we need a planet that spent billions of years evolving with us. We depend completely on the billions of other living organisms that make up Earth’s biosphere. Without them, we cannot survive. Astronomical observations and Earth’s geological record are clear: the only planet that can support us is the one we evolved with. There is no plan B. There is no planet B. Our future is here, and it doesn’t have to mean we’re doomed.

[Imagine] "we have landed on a perfect twin of the Archean Earth, the aeon during which life first emerged on our home world. This new planet is certainly habitable: lifeforms are floating around the green, iron-rich oceans, breathing out methane that is giving the sky that unsettling hazy, orange colour. This planet sure is habitable – just not to us. It has a thriving biosphere with plenty of life, but not life like ours. In fact, we would have been unable to survive on Earth for around 90 per cent of its history; the oxygen-rich atmosphere that we depend on is a recent feature of our planet.

"The earliest part of our planet’s history, known as the Hadean aeon, begins with the formation of the Earth... the early Hadean would have been a terrible place with molten lava oceans and an atmosphere of vaporised rock. Next came the Archean aeon, beginning 4 billion years ago, when the first life on Earth flourished. But, as we just saw, the Archean would be no home for a human. The world where our earliest ancestors thrived would kill us in an instant. After the Archean came the Proterozoic, 2.5 billion years ago. In this aeon, there was land, and a more familiar blue ocean and sky. What’s more, oxygen finally began to accumulate in the atmosphere. But let’s not get too excited: the level of oxygen was less than 10 per cent of what we have today. The air would still have been impossible for us to breathe. This time also experienced global glaciation events known as snowball Earths, where ice covered the globe from poles to equator for millions of years at a time. Earth has spent more of its time fully frozen than the length of time that we humans have existed.

"Earth’s current aeon, the Phanerozoic, began only around 541 million years ago with the Cambrian explosion – a period of time when life rapidly diversified. A plethora of life including the first land plants, dinosaurs and the first flowering plants all appeared during this aeon. It is only within this aeon that our atmosphere became one that we can actually breathe....From the point of view of our planet, the changes leading to these mass extinctions are relatively minor. However, for lifeforms at the time, such changes shattered their world and very often led to their complete extinction.

***

" No, we call this planet our home thanks to its billion-year-old relationship with life. Just as people are shaped not only by their genetics, but by their culture and relationships with others, planets are shaped by the living organisms that emerge and thrive on them. Over time, Earth has been dramatically transformed by life into a world where we, humans, can prosper. The relationship works both ways: while life shapes its planet, the planet shapes its life. Present-day Earth is our life-support system, and we cannot live without it.

"Looking at Earth’s long history, we find that we would have been incapable of living on our planet for most of its existence. Anatomically modern humans emerged less than 400,000 years ago; we have been around for less than 0.01 per cent of the Earth’s story. The only reason we find Earth habitable now is because of the vast and diverse biosphere that has for hundreds of millions of years evolved with and shaped our planet into the home we know today. Our continued survival depends on the continuation of Earth’s present state without any nasty bumps along the way. We are complex lifeforms with complex needs. We are entirely dependent on other organisms for all our food and the very air we breathe. The collapse of Earth’s ecosystems is the collapse of our life-support systems.
***

"Earth is the home we know and love not because it is Earth-sized and temperate. No, we call this planet our home thanks to its billion-year-old relationship with life. Just as people are shaped not only by their genetics, but by their culture and relationships with others, planets are shaped by the living organisms that emerge and thrive on them. Over time, Earth has been dramatically transformed by life into a world where we, humans, can prosper. The relationship works both ways: while life shapes its planet, the planet shapes its life. Present-day Earth is our life-support system, and we cannot live without it." (my bold)

Comment: this supports my statement that the Earth had to evolve to allow our appearance. So dhw's 'humans plus food' derisive comment is an incomplete assessment of God's work. The evolution of a giant bush of life evolved the Earth to a point that humans could be supported. I've known this all along. I should have presented this view earlier and there would have been less misunderstood discussion.