Part 1: Emergence of Life
Laws of Physics and Initial Conditions of Universe
Everything observable in the universe can be explained elegantly by a few basic building blocks called fundamental particles, governed by four fundamental forces. The Standard Model of particle physics along with Gravity constitute the fundamental laws of physics.
We live in the aftermath of a large event — The Big Bang. We don’t yet have an explanation for this event, but it has led to the creation of all the fundamental particles and forces. The interplay of these particles and forces with more unexplained factors like Dark Matter and Dark Energy has created everything that we see around us the way it is. In the next few sections we will dive deeper into how Big Bang and the fundamental forces have led to the evolution of universe and thereby life.
Emergence of Complexity
One apparent defining feature of life is it’s complexity. A complex system is one that cannot be explained “simply” from the interactions of it’s constituent parts or “agents”. Complex systems emerge when there are a large number of agents that are mutually interacting based on simple rules, giving rise to emergent properties and entire new class of entities. Big Bang has provided the universe with these agents — aka the fundamental particles and rule — the 4 fundamental rules.
Evolution and Increasing Complexity
Evolution by natural selection is widely accepted as the reason for increasing complexity of life on Earth. Evolution is not constrained to biology. It is the basic principle behind the emergence and increasing complexity of nearly all complex systems. Merging and splitting of agents is one of the basic mechanisms which increase complexity. This increase is often accompanied by instability and therefore temporary.
To increase complexity permanently, the emergent entities must be stable. Starting from the creation of first atoms, evolution helped increase complexity by finding stable and increasingly complex entities. Fundamental particles evolved into atoms of Hydrogen and Helium; evolution and eventual death of stars created heavier elements; which in turn formed molecules and compounds of increasing complexity.
“Emergence” of Life
Typical characteristics of an entity with life include preserving and reinforcing it’s existence in a given environment. This requires a cell membrane for clear demarcation between self and the environment and reproduction for preserving and reinforcing it’s existence. The emergence of life and it’s properties can be attributed to gradual increase in complexity. Auto-catalytic reactions sustained the complexity, evolution of cell membranes helped with preservation against adverse environmental factors and self-replication/self-assembly helped reinforce and increase complexity.
Emergence of life can be summarized into two phases — Chemical evolution followed by Biological evolution that led to the evolution of biological monomers (nucleotides, amino acids etc.) followed by biological polymers (RNA, DNA, proteins etc.) and eventually cells and complex life forms. Every stage of increasing complexity is characterized by emergence of new complex features and properties.