One of the complaints I often hear from otherwise knowledgeable doubters of evolution is that science has not found out how life got started in the first place. This is invariably followed by there needing to be a supernatural cause. To use a crude analogy, if I find rat droppings in my house, but can’t see how the rat could have gotten in, this does not inexorably lead to a conclusion that a divine Rat Placer put the rat there. It just means that I haven’t found out yet how the rat got in. On the question of the origins of life, we have a difficult problem, to be sure. The fact that a problem is difficult does not necessarily mean that the solution is supernatural.
What makes the problem difficult is that there are a daunting number of variables. We don’t know precisely where molecules first started utilizing energy to reproduce themselves, or precisely what the environment was like in which it happened. The whole planet was the stage with varying environments and billions of molecular reactions going on for nearly a billion years. We can make some reasonably educated guesses and go from there though. Of course, even if we succeed in creating synthetic life, there could still be some uncertainty if what we produced was what actually happened. There could perhaps be a multiplicity of ways for things to get started. That doesn’t mean we stop looking though.
So, it was interesting to see this recent article from PhysOrg.com on this very question.
“I look at the origin of life as the result of combinatorial chemistry on a global scale,” said Deamer, a research professor of chemistry and biochemistry at UCSC who is also affiliated with the Department of Biomolecular Engineering in UCSC’s Jack Baskin School of Engineering.
The power of combinatorial chemistry lies in the vast numbers of structurally distinct molecules that can be synthesized and tested at the same time. Similarly, conditions on the early Earth allowed not only the synthesis of a wide variety of complex organic molecules, but also the formation of membrane-bound compartments that would have encapsulated different combinations of molecules.
“We have made protocells in the lab–artificial compartments containing complex systems of molecules,” Deamer said. “The creationists charge that it’s too unlikely for the right combination to have come together on its own, but combinatorial chemistry gives us a better way to think about the probability of life emerging from this process.”
In other words, the space of chemical combinations that could have gotten life started is enormous. As the molecules became organized and utilized resources for growth and reproduction, a confined space, as the article goes on, means that there will be competition for resources. It is evolution at the biochemical level. Some chemical strategies will be more successful than others.
It is interesting that membrane bound compartments were mentioned as one of the pieces of the puzzle needing to eventually fit. Not too long ago it was proposed that the function of the cellular membrane may have been performed by sheets of mica (also discussed here. It is interesting speculation. From the Astrobiology.com article:
Hansma says that her “soup and sandwich” mica hypothesis is supported by several lines of evidence, including the many chemical and physical similarities between a cell interior and the space between mica sheets. For example, both environments are potassium-rich and negatively-charged. Such similarities suggest that mica “would have provided a very hospitable environment to the earliest biomolecules,” says Hansma.
In addition, the confined spaces formed by mica layers would have provided the isolation needed for Darwinian evolution. What’s more, the expansion, contraction and movements of the mica sheets caused by temperature changes and ocean currents would have helped rearrange molecules and trigger the formation of bonds between them, as required for life to originate.
The mica boundaries could have acted as de-facto primitive membranes. It is an intriguing idea, but since Hasma first proposed this a couple of years ago, I haven’t read anything else about it. I would be interested to see any experimental results with likely chemical combinations between mica, in effect trying to emulate those possible early Earth conditions. It’s stuff like this that makes me want to build a lab in the garage. Then, of course, get funding, hire a team and find collaborators, make a clean room to make sure everything is sanitized (including the mica) to rule out false positives, etc. etc. It’s hard to be a mad scientist creating life these days.