"In 1953, a graduate student at the University of Chicago named Stanley Miller, along with his faculty advisor Harold Urey, performed experiments hoping to produce the building blocks of life under natural conditions on the early Earth. These "Miller-Urey experiments" intended to simulate lightning striking the gasses in the early Earth's atmosphere. After running the experiments and letting the chemical products sit for a period of time, Miller discovered that amino acids -- the building blocks of proteins -- had been produced.
For decades, these experiments have been hailed as a demonstration that the "building blocks" of life could have arisen under natural, realistic Earthlike conditions,corroborating the primordial soup hypothesis. However, it has also been known for decades that the Earth's early atmosphere was fundamentally different from the gasses used by Miller and Urey.
The atmosphere used in the Miller-Urey experiments was primarily composed of reducing gasses like methane, ammonia, and high levels of hydrogen. Geochemists now believe that the atmosphere of the early Earth did not contain appreciable amounts of these components. UC Santa Cruz origin-of-life theorist David Deamer explains in the journal Microbiology & Molecular Biology Reviews:
'This optimistic picture began to change in the late 1970s, when it became increasingly clear that the early atmosphere was probably volcanic in origin and composition, composed largely of carbon dioxide and nitrogen rather than the mixture of reducing gases assumed by the Miller-Urey model.'"Seems you shouldn't believe everything your high school science teacher says! Personally, I worked that one out in my twenties when I read a number of books on the new physics and cosmology and discovered our science teacher's cosmology - the steady-state theory of the universe - had been challenged both theoretically and empirically for the best part of the 20th century. One of the most compelling arguments against naturalism I came across was in connection with Sir Fred Hoyle's theory that life was cast to earth by some extra-terrestrial intelligence. Having already become familiar with the then most recent mathematical calculations regarding the probabilility of intelligent life existing elsewhere in the universe, it seemed simpler to me to posit a super-natural creator, and from there I adopted a philosophical belief in the Christian God. Actual faith came somewhat later and is another story altogether. But enough of my thoughts... it seems the myth of the Miller-Urey exoeriemnt is a long time dying; for a short assesment of the top five problems with current naturalistic theories of the origins of life on earth, go here.