London, September 16 : A new research ahs pointed out that evolution might have existed even before the advent of life on Earth, in the form of natural selection that likely existed in the primordial soup billions of years ago.
Most experts presume that life arose from complex molecules such as nucleic acids and proteins, which were assembled from a mix of simpler units strung together with chemical bonds.
To examine how this might occur, Martin Nowak and Hisashi Ohtsuki, mathematical biologists at Harvard University, used simple equations to model the growth of such chains of building-blocks.
According to a report in New Scientist, the model shows that because longer chains require more assembly reactions, they should be much less common than short chains.
If some assembly reactions run faster than others, then chains built from these fast-assembling sequences of building blocks grow to be most abundant.
This bare-bones equivalent of natural selection makes the prebiotic soup an interesting place, according to the researchers.
"It generates a rich evolutionary dynamic - or what I would want to call a 'prevolutionary' dynamic - where you have diversity, you have information, you have complicated chemistry," said Nowak.
Such a system, full of novel, interacting molecules, would be the ideal milieu to generate a molecule with attributes that would favour the assembly of copies of itself. owak's prebiotic selection could then act to refine this ability by ensuring that better replicators become more common.
At some point, Nowak's model predicts, the best replicator may get fast and accurate enough to dominate the population, sucking up all the resources and driving all the other prebiotic sequences extinct.
This is the threshold of life.
"Ultimately, life destroys pre-life. It eats away the scaffold that has built it," said Nowak.
In showing that selection actually precedes the origin of life, and helps to shape it, Nowak helps bridge the gap between nonliving and living systems.
In a sense, the prebiotic soup is constantly testing possible replicators, making it much more probable that one might eventually reach the threshold of life.
According to Irene Chen, an origin-of-life researcher also at Harvard, Nowak's model helps clarify a murky area of research on prebiotic mixtures.