Before life emerged on earth, either a primitive kind of metabolism or an RNA-like duplicating machinery must have set the stage so experts believe. But what preceded these pre-life steps?
A pair of UCSF scientists has developed a model explaining how simple chemical and physical processes may have laid the foundation for life. Like all useful models, theirs can be tested, and they describe how this can be done. Their model is based on simple, well-known chemical and physical laws.
The work appears online this week in The Proceedings of the National Academy of Sciences. ( http://www.pnas.org/cgi/content/abstract/0703522104v1)
The basic idea is that simple principles of chemical interactions allow for a kind of natural selection on a micro scale: enzymes can cooperate and compete with each other in simple ways, leading to arrangements that can become stable, or locked in, says Ken Dill, PhD, senior author of the paper and professor of pharmaceutical chemistry at UCSF.
The scientists compare this chemical process of search, selection, and memory to another well-studied process: different rates of neuron firing in the brain lead to new connections between neurons and ultimately to the mature wiring pattern of the brain. Similarly, social ants first search randomly, then discover food, and finally build a short-term memory for the entire colony using chemical trails.
They also compare the chemical steps to Darwins principles of evolution: random selection of traits in different organisms, selection of the most adaptive traits, and then the inheritance of the traits best suited to the environment (and presumably the disappearance of those with less adaptive traits).
Like these more obvious processes, the chemical interactions in the model involve competition, cooperation, innovation and a preference for consistency, they say.