Origin Of Life On Earth: Simple Fusion To Jump-start Evolution
With the aid of a straightforward experiment, researchers have provided some clues to one of biology's most complex questions: how ancient organic molecules came together to form the basis of life.
Specifically, this study demonstrated how ancient RNA joined together to reach a biologically relevant length.
RNA, the single-stranded precursor to DNA, normally expands one nucleic base at a time, growing sequentially like a linked chain. The problem is that in the primordial world RNA molecules didn't have enzymes to catalyze this reaction, and while RNA growth can proceed naturally, the rate would be so slow the RNA could never get more than a few pieces long (for as nucleic bases attach to one end, they can also drop off the other).
Ernesto Di Mauro and colleagues examined if there was some mechanism to overcome this thermodynamic barrier, by incubating short RNA fragments in water of different temperatures and pH.
They found that under favorable conditions (acidic environment and temperature lower than 70 degrees Celsius), pieces ranging from 10-24 in length could naturally fuse into larger fragments, generally within 14 hours.
The RNA fragments came together as double-stranded structures then joined at the ends. The fragments did not have to be the same size, but the efficiency of the reactions was dependent on fragment size (larger is better, though efficiency drops again after reaching around 100) and the similarity of the fragment sequences.
The researchers note that this spontaneous fusing, or ligation, would a simple way for RNA to overcome initial barriers to growth and reach a biologically important size; at around 100 bases long, RNA molecules can begin to fold into functional, 3D shapes.
Entropy is the tendency of a system to disorder, like an ice cube melting or a car rusting. Life is a localised example of negative entropy, where times arrow runs backwards, which is an amazing thought (thank you Schrödinger).
Studies like this are really cool, they are showing the biochemical origins of the magnificent complexity that we are part of, and how it can originate through large numbers of chemical reactions. It demonstrates the types of chemical processes which can develop life, both on Earth and elsewhere in the universe.
For those who are interested, it isn't blind chance which created all the complex life in the world (and around it, in space stations); it is the preferential selection of different forms in varying populations due to environmental conditions. Blind chance is not a viable explanation for complex life, natural selection - which would have begun acting on the first self-replicating and varying molecules - is.