»Die Welt«, 15/05/03

50 years ago, Stanley Miller cooked the primordial soup of life (by Ulli Kulke)

Berlin – The experiment had Frankenstein-like qualities. In Chicago, 50 years ago today, a 23-year old student was working with a mysterious apparatus in his lab. He added a small amount of methane and ammonia to an array of connected glass tubes and flasks, and then exposed these inorganic substances to steam from distilled water and sent occasional electrical arcs - simulating lightning - through the cloudy material. After two days, he had obtained the building blocks of life: the products included 20 amino acids, the basic components of proteins, and carbohydrates …

… The primordial soup that Miller had cooked up caused a sensation. It fit the times. After all, hadn't Watson and Crick deduced the structure of DNA only a few weeks earlier? Was humankind, now in a spirit of optimism after the world war, on the verge of discovering the last secrets of life?

Miller's results convinced Harold Urey, who had won the Nobel Prize for chemistry in 1934. Urey personally contacted the renowned journal “Science” and helped Miller to world fame. The connection between lightning and life fascinated everyone, not only experts. The primordial soup was quickly incorporated into comic books, science fiction novels and films.

But Miller's breakthrough suffered many setbacks in the following years. For instance, other researchers had already carried out similar experiments before him. Before World War One, the German chemist Walther Löb had already used similar ingredients and electric arcs to create amino acids, and even earlier, in 1828, Friedrich Wöhler successfully synthesised the organic compound urea from ammonium cyanate. Nevertheless, these experiments refuted the idea that life had emerged spontaneously.
However, some scientists remained sceptical as to whether the primordial soup generated on Earth was indeed the origin of life. No-one knows what conditions were like on Earth four billion years ago when life is presumed to have begun. Amino acids would not have been able to exist if they were exposed to the sun's UV rays. At that time, there was no atmospheric oxygen that would have produced a protective ozone layer. The early nucleus of life on Earth would have been lost before it took hold – unless everything took place in water, which would have caused problems with the lightning. Of course, these constraints also apply to the alternative hypothesis which suggests that the building blocks of life on Earth came from the cosmos.

Miller is still working as a biochemist at the University of California in the USA.