Artistic conception of Titan’s surface. The discovery of methane lakes on this Saturn satellite indicates that its environment may be similar to what it was on primitive Earth, when life on our planet appeared.
Our cells are composed of water and carbon, hydrogen, oxygen and nitrogen atoms, in addition to smaller amounts of other chemical elements. These components have nothing special and are also found dispersed on our planet and in inhospitable places in the universe. However, if we put them in a container with water and gave a good shake, we would not get a living being by magic. For life, despite being based on simple ingredients, has an intricate and delicate arrangement that, to be created, took an enormous amount of time.
Among the known organisms that have a cellular organization, the bacterium Mycoplasma genitalium is the species with the simplest genome. It has only 482 genes, four times less than the famous Escherichia coli. However, some scientists claim that these bacteria still have many genes in addition to the minimum number needed to maintain a living being with functional cell organization, which would be just over 200.
Even prokaryotes with a simplified cellular organization, such as this species of Mycoplasma, present a complexity far superior to that of any artifact created by our technology. Understanding how a genome was formed – even the simplest of them – and all other cellular components and understanding how the subunits work together and harmoniously are not easy tasks.
This complex arrangement is the result of gradual processes that have been shaped under the baton of natural selection since our planet began to offer minimal conditions for life to establish itself here. The first stages of the life formation process are considered the most delicate and complex. For this reason, it is believed that they demanded more time and that obtaining the first organic molecules was a more difficult stage to be overcome than all the following evolutionary stages, which culminated in the development of multicellular organisms like ours.
Apparatus created to reproduce the Miller-Urey experiment, which showed that it was possible to obtain primordial molecular compounds by applying electrical stimuli to a mixture of gases and water (photo: NASA).
The hypothesis traditionally mentioned to explain the origin of life is known as the “primordial soup” theory. This assumption, independently proposed in the 1920s by the Russian Alexsandr Oparin (1894-1980) and the British J.B.S. Haldane (1892-1964), states that life would have gradually emerged from casual contacts between simple molecules in an environment with abundant energy sources – such as a small lake, for example.
This hypothesis was viewed with skepticism until an experiment carried out in 1953 by the American chemist Harold Urey (1893-1981 – Nobel winner for the discovery of deuterium) and by his student Stanley Miller showed that it was possible to obtain primordial molecular compounds from application of electrical stimuli to a mixture of simple gases and water. This elegant experiment catapulted them both to fame.