One of the “big questions” of humanity is the question of how life originated on our planet. Until well into the 20th century, scientists have hardly dealt with this question, as they had considered it outside their scope. But with the Darwinian theory of evolution in the second half of the 19th century and its systematic anchoring (along with genetics) in the structural theory of biology in the 40s of the 20th century, the question of the origin of life appeared on the scientific radar. A final answer has not been found until today. However recently a little more light fell on this question.
Since the 1940s, we know that in any occurring form of life on our planet certain chemical compounds appear as elementary building blocks. These are amino acids, nucleic acids and carbohydrates (sugars). The search for an answer to the question of the origin of life therefore initially consists of how these building blocks – one could say “early messengers of life” – may have been formed (note the auxiliary verb here). In a sensational experiment, science succeeded on that task as early as 1953, the same year in which the structure of DNA was discovered. The geologists had already suspected that the main constituents of the atmosphere around two to three billion years ago, rather than the current ones being mainly nitrogen and oxygen, were hydrogen-based molecular compounds, in particular methane (CH4) and ammonia (NH3). The two US scientists Stanley Miller and Harold came up with the idea to recreate the former conditions on our planet in a simple experiment. To this end, they combined in a vessel of water ammonia, methane and hydrogen (the “earthly primordial soup”) and exposed this solution to strong UV radiation and electrical discharges (lightning). Violent lightning and thunder, intense ultraviolet radiation from the sun, which an unprotected early earth were exposed to, together with combinations of certain inorganic substances that rained down into the sea, should have made it possible, as the researchers suspected, that spontaneously complex organic molecule formed in the compounds which then could develop into amino acids, proteins, and nucleic acids.
And indeed: At the end of the experiment, Urey and Miller were able to identify simple amino acids in the solution! After longer exposure times even more complex amino acids had formed. Finally they found exactly those 20 amino acids that we find today in living organisms! (later two more were found). Thus, a possible scenario for the origin of the basic building blocks of life was revealed. We now had a scientific answer to the most basic question of where amino acids could come from.
Although this constituted a first important step towards the explanation of life, the path towards its complete understanding remains long even today. The details of the development from simple chemical building blocks towards cells and more complex life forms with metabolism, self-reproduction and evolution remain absolutely unclear. The next step towards this goal was the question of how the more complex molecules adenine, guanine, cytosine, thymine, and uracil (nucleotides), the elementary pieces of genetic information carrier DNA and RNA, could potentially have developed.
Precisely for this step the scientists have in recent weeks obtained new insights. For long many researchers have believed that the key biochemical molecules had come from asteroids from space crashing to Earth- There is now evidence that they could well have formed on Earth. However, the giant impacts from space may have nevertheless played an important role. In a rather fierce version of the classic Urey-Miller experiment Czech biochemist around Svatopluk Civis imitated the local conditions of an asteroid strike using high power lasers. They sent ultra-intense laser pulses into the “Urey-Miller primordial soup”, which furthermore contained the biochemical precursor molecules of formamide (that according to the presumption of the scientists was part of the primordial atmosphere). They thus created conditions that were likely to be present in the vicinity of an asteroid impact. The chemical reactions that take place under these conditions, are hardly the same as those occurring under normal conditions. To the delight of the researchers at the end of the experiment they found in the solution all of the nucleotides listed above that make up the genetic molecules.
This constitutes another (possible) piece of the puzzle in the search for an answer to one of the great questions of humanity. However, we note that science is intrinsically open, i.e. we never know whether we are actually on the right track. However, we can say as much as this: Science is increasingly able to draft contours of a possible answer to the question of the origin of life (thereby also rejecting many non-scientific answers). Would a “breakthrough” such as the one this month not merit a little more coverage in the public domain? Unfortunately we, the consumers of today’s media, are searching with little success when science has some news like this to offer.