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.

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?