The Making of Life on Earth: From the first chemistry to the present biosphere, step by step

Life on Earth is a single lineage that began from chemistry, perhaps within two or three hundred million years of the first oceans, and has since rebuilt the planet that made it. This paper follows that history in order. It starts with the building blocks, some delivered from space and some made on the young Earth; follows them into short strands of RNA, molecules that copy themselves, membrane-bound protocells, the genetic code and proteins, and DNA; and arrives at the last universal common ancestor of all living things, estimated at about 4.2 billion years ago. It then traces what life did to the oceans and the air: methane and carbon dioxide in a world without oxygen, nitrogen drawn from the air, the invention of oxygen-producing photosynthesis, the Great Oxidation Event beginning 2.43 billion years ago, the rusting of iron out of the oceans, the ozone layer, complex cells, two global glaciations, the first animals, calcium skeletons in the Cambrian, plants and forests on land, five mass extinctions, the cooling Cenozoic, and the arrival of humans. It ends with the present, in which one species has raised atmospheric carbon dioxide from about 280 to 432 parts per million. It makes no claim about the future of Earth or of life on it. A timeline (Figure 1, Table 2) and an element ledger (Table 3) record what happened when and what life did to each element. The arc is the history of the universe from creation to crunch in the Euler Cosmos, measured by the phase θₜ = H₀t, which runs from 0 at creation through 0.881 now to about 3.95 at the crunch. On the arc, life begins near θₜ ≈ 0.61, the air fills with oxygen at 0.725, animals appear at 0.84, and the whole existence of Homo sapiens lies within the last 0.00002 of the arc traversed. Every quantity is imported from the sciences of life and Earth. The contribution is the ordering: one continuous record from the first chemistry to the present biosphere, read alongside the planet it changed.