The survey is absurd. As like the first human, the first atom, the first star, there was never a first cell. There were populations of pre-cells first and before that pre-pre-cells … Lot of chemical processes going on before biochemical processes. Perhaps going on for hundred of millions of years at many places on Earth, in fits and starts until it seems that what we call life took root around 4 billion years ago. Then a real long time (a billion years) before multicelluar life.
Good book to read:
https://www.amazon.com/New-History-Life-Discoveries-Evolution/dp/160819910X
The authors begin by discussing the geological eras and periods of the past. The Cryogenian (850-635 million years ago) and Ediacaran (635-542 million years ago) periods are important to this new understanding of life. But first we shift back to about 4.6 to 4.5 billion years ago, where we learn the importance of the oxidation-reduction cycle, the carbon cycle, and how chemical weathering and greenhouse gases affect global temperature. It is during this period, that the planet becomes Earthlike. We also learn the definition of life: life metabolizes, it reproduces, it evolves, etc. Knowing this is important in order to recognize it in the fossil record. There are three main branches: Archaea, Bacteria and Eucarya (we’re in this group).
The next period is from about 4.2 to 3.5 GA (GA means billions of years). It is during this period we find the first signs of life on the planet. Interesting the earliest life lived in the sea, needed sulfur to survive, and died if exposed to oxygen. In the next chapter, we cover the period 3.5 to 2.0 GA. In this chapter we see clear evidence of the photosynthetic cyanobacteria that produced oxygen (Earth was pretty much devoid of oxygen before this) and the evidence for this oxygen via the disappearance of pyrite and uraninite and the change in pattern of sulfur isotopes. It appears an oxygen-rich atmosphere was present by about 2.22 GA with a massive oxidation event at 2.1 GA according to pure hematite iron-ore deposits dated to that time.
The next period discussed covers time from 2.0 to 1.0 GA. This period is called the “boring billion,” as it is the time since the great oxygenation event and the appearance of more complex multicellular life. We also see a “snowball Earth” event here that seemed to jack up oxygen levels via a post-snowball algal bloom. Another such event occurred and ended prior to the Cambrian period. Finally we get to the period from 850 to 535 MA (millions of years). The case is made by the authors that the snowball Earth episodes of this period were key to the sudden rise of animals.
In each subsequent chapter, the authors cover a particular time period moving closer and closer to the present time. The next chapter covers the Cambrian Explosion (600-500 MA). This turned out to be a very detailed, information-packed chapter, which I found very informative. We continue to move through time covering the Ordovician-Devonian periods, the Carboniferous-Permian oxygen high and its effect on animal life on land and so on. Chapter XIX, the next to last chapter, covers 2.5 MA to the present.
The authors present for us a very detailed biography of the life on Earth. I found the book very fascinating and illuminating. I have come away with a much clearer picture of the ebb and flow of life over hundreds of millions of years. I mark this as one of my favorite books on the subject of evolution.
