Once cooperation had evolved the first cell there were apparently metabolic processes inside of it that could not simply keep getting bigger. Instead, the growing cell divided, and then kept on dividing. There were few limits in the early ocean. Two questions are examined: first, how does the individual bacteria make decisions, and second, what is the extent of the bacterial world that came to inhabit the surface of the early Earth?
Current genetic research has examined many life forms for the basic metabolic processes and molecules that are shared by all forms of life. These common processes are projected backwards to a simple, undifferentiated common ancestor called LUCA (the last undifferentiated common ancestor).
Even Luca had complexity far beyond our current ability to explain. One possible step beyond the self- generating metabolic processes described in the last chapter, is the vision of “RNA world”. The RNA molecule is a spiral that is half of the DNA that currently encodes the proteins of life. It is possible that early RNA molecules were chief cook and bottle washer, combining not only the reproductive library function of DNA, but also the protein-fabricating role of ribosomes. Thus this molecule could have both regulated and created the early cell.
This may be the next step in the journey of life. We are only beginning to understand how such a cell regulates itself and makes decisions. Vertebrates have brains and nervous systems, yet all forms of life take in information and make decisions. Maps of protein-fabricating networks in the simplest bacteria are too complex to explain, but behavior seems to emerge from them. Such networks have been mapped, and are called “interactomes”. They are being researched also in larger cells, in plants and in fungi. The idea of the interactome will be important later in the book.
Free swimming bacteria were the vast majority of life for billions of years on Earth. There may also have been a layer of bacteria that carpeted the bottom of the ocean, and extended, as it does today, more than a mile into the rocks of the crust. This bacterial life became host for the next cooperative stage of life, in the same way that cooperatively structured watered had been its host. But there is a lot to say, or at least ask, about this huge bacterial world before we move on.
Bacteria do not have sex or sexes, yet they constantly exchange genes in a variety of ways. The concept of a species depends on gene staying put inside of particular genetic lineages. A study of one “species” of ocean bacteria found that most of them came from different genetic lineages. The differences between species of bacteria is about different metabolisms: what they eat and what they excrete. Bacteria eat everything from iron to sunlight and excrete a wide variety of industrial chemicals like acetone and even electrons.
There may be millions of kinds of bacteria. If the different species of bacteria do not depend on their lineages, then these “species” may be better described as “job descriptions”. If that is the case, then what vast communal functioning has roles for so many different players?