Much of the evolution and creation debate devolves into "what about the origin of life" question despite the fact that evolutionary biology only explains the diversification of life once it has gained a foothold on earth. The field of natural origin of life (abiogenesis) is still in its infancy and there have been some good threads on it already. Here I would present a bit of an overview kind of discussion on where science is on this and what advances and challenges remain.
The basic concept of abiogenesis can be summarized using the figure below (book: the emergence of life 2nd ed.)
1) We initially have a stage if chemical evolution, when simple organic molecules present in early earth increased in complexity through chemical evolution to the prebiotic building blocks of life (bases, sugars, amino acids etc.) The fact that this can happen on early earth has been plausibly demonstrated by lots of research into chemical evolution. They have been covered in my earlier thread. LINK
2) The next phase goes into what is called molecular evolution where the building blocks of the eventually complex nucleic acids, bases, sugars, lipids etc. come together (maybe in proto cellular compartments) and engage in molecular evolution to create the complex macromolecules that enter into self-sustaining reactions that kick start life. Here we need to have the emergence of metabolic networks (reaction networks that interconnect and generate these macromolecules cyclically), the genetic code and the compartments that keep the important components of the reaction network together. This part has proven more difficult and I will focus more here, in this 2nd crucial phase to the transition to life.
One question that often comes up here is how can complexity spontaneously arises from simplicity when that would mean that the entropy of the system decreases? Of course, it happens all the time...for example during winter, the frozen ice crystals are much more complex in their structure than the liquid water it comes from. It is important to know that the science of thermodynamics does not say that entropy (S) cannot decrease in a spontaneous natural process. In thermodynamics we use a term called free energy (G) and what thermodynamics actually says is that: For any spontaneous process, the free energy of a system must decrease from its initial value at the beginning of that process. One defines free energy as:
Free Energy (G) = Thermal Energy (H) - Temperature*Entropy(S).
Clearly, if other terms remain constant and the entropy rises, then the Free Energy will fall making the process spontaneous. But note that entropy can decrease (system becomes more complex and ordered) and still the free energy can decrease if the decrease in thermal energy (H) is greater than the fall in entropy. This is precisely what happens when liquid water freezes, it releases a lot of heat into the surrounding leading to a fall in its thermal energy. This is just one of many many ways that the laws of thermodynamics will allow a system to decrease its entropy in a spontaneous fashion. Thus, from physical law point of view, we have no concern. It is understanding the molecular processes that led to the emergence of life like systems from the bio-molecular building blocks that will concern us. More on this in the next post.
Comments, thoughts? Welcome!
The basic concept of abiogenesis can be summarized using the figure below (book: the emergence of life 2nd ed.)
1) We initially have a stage if chemical evolution, when simple organic molecules present in early earth increased in complexity through chemical evolution to the prebiotic building blocks of life (bases, sugars, amino acids etc.) The fact that this can happen on early earth has been plausibly demonstrated by lots of research into chemical evolution. They have been covered in my earlier thread. LINK
2) The next phase goes into what is called molecular evolution where the building blocks of the eventually complex nucleic acids, bases, sugars, lipids etc. come together (maybe in proto cellular compartments) and engage in molecular evolution to create the complex macromolecules that enter into self-sustaining reactions that kick start life. Here we need to have the emergence of metabolic networks (reaction networks that interconnect and generate these macromolecules cyclically), the genetic code and the compartments that keep the important components of the reaction network together. This part has proven more difficult and I will focus more here, in this 2nd crucial phase to the transition to life.
One question that often comes up here is how can complexity spontaneously arises from simplicity when that would mean that the entropy of the system decreases? Of course, it happens all the time...for example during winter, the frozen ice crystals are much more complex in their structure than the liquid water it comes from. It is important to know that the science of thermodynamics does not say that entropy (S) cannot decrease in a spontaneous natural process. In thermodynamics we use a term called free energy (G) and what thermodynamics actually says is that: For any spontaneous process, the free energy of a system must decrease from its initial value at the beginning of that process. One defines free energy as:
Free Energy (G) = Thermal Energy (H) - Temperature*Entropy(S).
Clearly, if other terms remain constant and the entropy rises, then the Free Energy will fall making the process spontaneous. But note that entropy can decrease (system becomes more complex and ordered) and still the free energy can decrease if the decrease in thermal energy (H) is greater than the fall in entropy. This is precisely what happens when liquid water freezes, it releases a lot of heat into the surrounding leading to a fall in its thermal energy. This is just one of many many ways that the laws of thermodynamics will allow a system to decrease its entropy in a spontaneous fashion. Thus, from physical law point of view, we have no concern. It is understanding the molecular processes that led to the emergence of life like systems from the bio-molecular building blocks that will concern us. More on this in the next post.
Comments, thoughts? Welcome!
. This equation is for things like routine chemical reactions in a lab, i.e. open to the atmosphere and to heat exchange with the environment. It therefore applies to a closed system but would be inapplicable to an isolated one, since enthalpy, H (= U+PV work) would not be a relevant quantity, nor would it be possible for entropy to decrease. 
