How Life Began on Earth

[Rhondazvous]

Sophie’s world is a novel of fiction. It also contains a lot of information about the history of philosophy from pre-Socrates to the existentialism of the 20th century.
But I’m whether the author may have taken fictional liberties concerning science.

When describing the philosophies of Darwin and his time, the character tells us that life must have developed before the earth had an atmosphere because DNA would have been oxidized by oxygen and destroyed. And this, according to the character, is why no new life can develop today.

I thought about this and based on what I think I know, it doesn’t seem right.
For one thing it assumes that life began as stand-alone DNA. So did it? Did the mitochondria and Golgi bodies and endoplasmic reticulum develop around the DNA at a later date?

Another thought is since life began in the ocean, there had to be an ocean for it to develop in. How do you have an ocean without oxygen? H2-0?

Can anyone here shed light on this?

[Kingpin]

Most hypotheses on early stages of life is really conjecture. We can certainly take best guesses, and each theory has it's own questions. So I don't think anyone can truly "shed light" as it were but discussing specifically these concerns perhaps. As far as actually how life began, well nobody really knows.

[vorlon13]

An oxygen atmosphere around a planet devoid of life (other than the mere wispy traces on such bodies like Europa) is pretty much impossible. So an oxygen atmosphere might (eventually) follow DNA formation but it would not precede it.

[Anomalocaris]

Sophie’s world is a novel of fiction. It also contains a lot of information about the history of philosophy from pre-Socrates to the existentialism of the 20th century.
But I’m whether the author may have taken fictional liberties concerning science.

When describing the philosophies of Darwin and his time, the character tells us that life must have developed before the earth had an atmosphere because DNA would have been oxidized by oxygen and destroyed.  And this, according to the character, is why no new life can develop today.

I thought about this and based on what I think I know, it doesn’t seem right.
For one thing it assumes that life began as stand-alone DNA. So did it? Did the mitochondria and Golgi bodies and endoplasmic reticulum develop around the DNA at a later date?

Another thought is since life began in the ocean, there had to be an ocean for it to develop in. How do you have an ocean without oxygen? H2-0?

Can anyone here shed light on this?

The oxygen you refer to is free oxygen molecules, O2 and O3, not oxygen atoms in chemical combination with other elements, like hydrogen, to form water H2O.

Earth always had just as many oxygen atoms as it does now. But prior to the great oxidation event around 2.3 billion years ago, all (and I mean all, as in 100% to literally 4 dozen decimal places) of earth's inventory of oxygen atoms were bound up in chemical bonds with other elements, including silica, hydrogen and carbon.

So there is plenty of sand, water, carbon dioxide, and various other oxygen bearing compounds, but no molecular oxygen. We know this how? We know experimentally that some of the minerals that are found in very ancient rocks can only form on the surface of the earth, but can not form except under conditions where the molecular oxygen content of the atmosphere is extremely close to zero, so close that the fractional partial pressure of free oxygen in the atmosphere had to have been zero to close to 40 decimal places.

So to answer your question, the ocean of salty H2O has existed on earth since at least 4.3 billion years ago. But until 2.3 billion years ago, the ocean was choked full of dissolved iron, and completely free of dissolved molecular oxygen. The air too had plenty of carbon dioxide, but zero free oxygen. Oxygen atoms were all there, but none of it is in the form of pure oxygen molecule.

[TheRealJoeFish]

Graphical form of what Anomalocaris said.  From Wikipedia page on "Great Oxygenation Event".  Essentially, life started over 3 billion years ago (maybe 3.5ish?) but O2 certainly wasn't around until 2.5 bya at the earliest, and didn't reach today's levels until relatively recently in the geological timescale

(In the picture the red and green are the upper and lower bounds, respectively, of the estimated oxygen concentration)

[Rhondazvous]

Graphical form of what Anomalocaris said.  From Wikipedia page on "Great Oxygenation Event".  Essentially, life started over 3 billion years ago (maybe 3.5ish?) but O2 certainly wasn't around until 2.5 bya at the earliest, and didn't reach today's levels until relatively recently in the geological timescale

(In the picture the red and green are the upper and lower bounds, respectively, of the estimated oxygen concentration)

Gee, the GEO is an amazing story. The way Wikipedia describes it, it reads like an epic drama. The very thing that makes our life possible was the bane of anaerobic organisms. The Oxygen Holocaust. So oxygen is the great geological Hitler. The Mussolini of the cosmos.

[Gawdzilla]

The fundies, the truthers, the deniers, all love to play gotcha science.

[Minimalist]

They are also all assholes.

[The Grand Nudger]

Sophie’s world is a novel of fiction. It also contains a lot of information about the history of philosophy from pre-Socrates to the existentialism of the 20th century.
But I’m whether the author may have taken fictional liberties concerning science.

When describing the philosophies of Darwin and his time, the character tells us that life must have developed before the earth had an atmosphere because DNA would have been oxidized by oxygen and destroyed.  And this, according to the character, is why no new life can develop today.

Most of earths "free" oxygen is attributable to life itself.  Oxygen is a byproduct of photosynthesis, the basis of all life on this planet, aerobic organisms did not (and could not) develop -until-  sufficient oxygen was present to respirate.  Earth had an atmosphere long before that atmosphere was approx 20% oxygen.  To say that life must have formed before earth had an atmosphere is ludicrous.

[Rhondazvous]

Sophie’s world is a novel of fiction. It also contains a lot of information about the history of philosophy from pre-Socrates to the existentialism of the 20th century.
But I’m whether the author may have taken fictional liberties concerning science.

When describing the philosophies of Darwin and his time, the character tells us that life must have developed before the earth had an atmosphere because DNA would have been oxidized by oxygen and destroyed.  And this, according to the character, is why no new life can develop today.

Most of earths "free" oxygen is attributable to life itself.  Oxygen is a byproduct of photosynthesis, the basis of all life on this planet, aerobic organisms did not (and could not) develop -until-  sufficient oxygen was present to respirate.  Earth had an atmosphere long before that atmosphere was approx 20% oxygen.  To say that life must have formed before earth had an atmosphere is ludicrous.

Set me straight, dear heart. I got it right but I tend to fuck up when I’m imprecise.

BTW, how did so much o2 wind up in the upper atmosphere? My understanding is that the ultraviolet rays of the sun cause o2 (ozone) to combine with water producing hydrogen peroxide which falls to the Earth to nourish the plants. Is o2 lighter than air, causing it to rise?