"PhysOrg.com) -- Life's ability to replicate itself is essential for evolution, yet even the simplest kind of replication requires a relatively complex system. So what kind of non-replicating system might have served as the predecessor of evolution, paving the way for life as we know it? The answer, according to a recent study, is a kind of "prelife" -- a chemical system that can lead to information and diversity, and that is capable of selection and mutation, but does not yet have the ability to self-replicate.

In their study, Hisashi Ohtsuki of the Japan Science and Technology Agency and the Tokyo Institute of Technology, along with Martin Nowak of Harvard University, have investigated how evolution might have first begun. As the researchers explain, the origin of life is a transition from chemistry to biology, and has been widely studied. Here, Ohtsuki and Nowak have presented a model where a purely chemical system (prelife) becomes more efficient (catalytic prelife) and then builds the sequences needed for replication, finally resulting in life. Their work is published in a recent issue of Proceedings of the Royal Society B.


"As you know, the ability of replication is critical for life," Ohtsuki told PhysOrg.com. "We can conceive several forms of life, such as prelife catalysts and replicators, as in our paper. We are interested in which form of life is most efficient and thus is selected in prelife (a soup of chemicals). The significance of our study is that we have mathematically shown for the first time that replicators, which have the ability to remain attached with a growing sequence, have a great advantage over the other forms of life. Replication is usually taken for granted in the study of evolution. We think that our result gives a justification of why replicators are so dominant."

In the scientists' model, prelife is made of two types of monomers (0 and 1) that randomly link together to form a polymer chain. By adding a 0 or a 1, longer chains are produced from shorter ones. The researchers created a simple tree of life based on this growth process, where either a 0 or a 1 is added to the end of the preceding chain to make a longer one. Though starting with just a single monomer, this tree of prelife has infinitely many lineages..."

From here.

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