> Life began in that alien environment, and at some point between 3.2 and 2.8 billion years ago, cyanobacteria began to use sunlight to split hydrogen from water, discarding oxygen as waste.
David Attenborough brilliantly explains the beginning of life and the role of cyanobacteria in the first episode of Life on Earth (1979), "The Infinite Variety,"[1] (in less than 20 minutes; doesn't need to be that long, but I wanted to catch him riding the mule, sooooo... strap in and enjoy).
The air was never unbreathable in any meaningful sense - it was altered in a way that provided an abundant new resource that permitted the evolution of new forms of life.
Life doesn't evolve to cope with anything. Life evolves as it adds variety and some of it gets cut down by the environment. Narratives implying teleology are misleading and wrong.
Metaphor is a common and delightful way to use language - you should try it sometime. It helps avoid the delusion that language has some inherent amount of rigor or correctness. Or that grammatical rules actually exist unchanging rather than being rules written by people making them up from the types of language and speaker that they approve of.
It's not clear why the Earth's oxygen has been somewhat stable since the Precambrian. If you kill all plants, oxygen goes away (reacting with reduced materials exposed by erosion and released in volcanism) in just a few million years. It could be an observer selection effect: if it had ever dropped too low in that time, we wouldn't be here now.
The calculations currently work out that the dumb luck is so incredibly lucky that it doesn't seem feasible to have happened in the observable universe due to the number of zeros involved.
But the whole point of the anthropic argument for anything (oxygen, goldilocks earth, fine tuning) is that it doesn't matter how slim the odds are. We cannot observe a universe where the lucky thing doesn't happen because we can't exist in such universe.
This is actually a very attractive book from a graphical design perspective. The content also looks enticing.
Kudos.
Edit: this section on the oxidation catastrophe implies that plants (seemingly) grew out of cyanobacteria. They did not. Basic eukaryotes that had a mitochondria came first, then plastids came after, with integration of new organelles. Plants are more evolved than us, from this perspective.
"Despite their tiny size, immense collections of cyanobacteria that bloomed across the oceans contributed to planet-wide ecological changes over time. These impacts include: oxygenating the atmosphere, originating plants, producing oil deposits, and energy efficient metabolisms. Cyanobacteria were so successful at taking in carbon dioxide that they narrowly caused their own extinction event. Many other microbes perished, too; however, life that had adapted to use oxygen flourished."
You are likely aware that there are (about) seven major classifications of plastids, and chloroplasts are but one. Chromoplasts are the only other that I remember offhand, and all came after the mitochondria.
"Cyanobacteria live just about everywhere on Earth that sunlight reaches: cold arctic tundra, Plant cells have an organelle called a chloroplast, which can be traced back to cyanobacteria, genetically."
I did not know about the molybdenum.
Again, this is a really nice book. I would read it to my kids.
> Life began in that alien environment, and at some point between 3.2 and 2.8 billion years ago, cyanobacteria began to use sunlight to split hydrogen from water, discarding oxygen as waste.
Think this is wrong. The discarded oxygen during photosynthesis comes only from splitting CO2.
"In general, photosynthesis in cyanobacteria uses water as an electron donor and produces oxygen as a byproduct, though some may also use hydrogen sulfide[77] a process which occurs among other photosynthetic bacteria such as the purple sulfur bacteria."
Carbon dioxide was breathable fuel for cyanobacteria prokaryotes.
The oxygen was their waste product, and it poisoned them when the concentration grew too high.
They had to wait for natural weathering to take the oxygen out of the atmosphere before they had another cycle of flourishing.
"Cyanobacteria are a very large and diverse phylum of photoautotrophic prokaryotes... cyanobacteria are thought to have converted the early oxygen-poor, reducing atmosphere into an oxidizing one, causing the Great Oxidation Event and the "rusting of the Earth", which dramatically changed the composition of life forms on Earth."
Rather, species evolved to survive within whatever the environment was at the time and also had an effect on the atmosphere itself, thereby killing other species in a very complicated dance.
It's a terrible title and a terrible article altogether.
> Biology, geology, and chemistry all worked together to make the present atmosphere.
No, no one "worked together".
And Earth never was an "Alien planet".
Life evolved alongside any challenges that a changing planet posed to it. Including changes induced by organisms.
Life still is evolving today and hopefully will continue to do so.
Also titles like this imply that the evolution of our planet and life is somehow guided or is directed to support humans. Or that humans are the crown jewel of evolution.
Au contraire. We are a pretty shitty product of evolution and are a danger to evolution itself since we acquired the intelligence and technology to change DNA of creatures based on our whims.
(We did this for centuries through artificial selection. Now we can do it more directly)
That's not the implication I got at all. Coupled with the photo, it really did seem like it would be an "Alien Plant" had I been able to be there. As far as "working together" - wow, you really look that literally. I don't think he meant they were conspiring by text on whatsapp.
Precisely — whatever ‘us’ is inferred to be, we’d have to be able to breathe whatever atmosphere we are immersed in. There’s selection bias at work here.
David Attenborough brilliantly explains the beginning of life and the role of cyanobacteria in the first episode of Life on Earth (1979), "The Infinite Variety,"[1] (in less than 20 minutes; doesn't need to be that long, but I wanted to catch him riding the mule, sooooo... strap in and enjoy).
[0] https://www.dailymotion.com/video/x2i43qc?start=673