14 DAY TRIAL // It is believed that the "primordial soup" is the place where natural selection began, even before there even was such a thing as life. This means that the prebiotic molecule complex may have increased the possibility for life to emerge.
The Krebs cycle refers to the way almost all organisms on the planet obtain their energy, by decomposing carbohydrates and generating carbon dioxide (CO2) in the most fundamental and ancient biochemical reaction. Reversing the Krebs cycle allowed scientists to use simple CO2 molecules, sunlight and 2 other compounds believed to have been present in the "primordial soup" and subject them to temperatures exceeding 100 °C in order to test the origins of life. This complies to the idea that life appeared from the assembly of complex molecules like proteins and nucleic acids comprised in a mixture of simpler units through the means of certain chemical bonds.
Another one of these studies was recently performed by mathematical biologists Martin Nowak and Hisashi Ohtsuki from Harvard University. They devised simple equations in order to estimate the development of these building-block chains. Based on their model, since longer chains need more assembly reactions, these should be a lot rarer while the chains built from building-block sequences with faster assembly reactions should be more common. Nowak explains: "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."
In such an environment, a self-replicating molecule is expected to arise and to specialize in this respect. Nowak's model estimates that at this level, the best of the replicators would become fast and accurate, able to destroy competition and render the rest of the prebiotic sequences extinct by consuming all the resources. So, in Nowak's theory, selection has existed before life and even helped shaping it and while proving that, he also linked life origins to non-living compounds. As Nowak sees it, by testing and selecting the replicators, nature pushed them to a certain goal, making the occurrence of life more and more probable.
We're still far from understanding all the processes involved though, especially since it has been recently discovered that we don't really know much about at least half of the features of our DNA or about the true complexity of our genes.