(Perhaps you have been misinformed on the definition of the word "atheist".
An atheist is a person that does not believe that deities exist. The definition goes no farther. An atheist may believe or disbelieve many other things and may have faith.)
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It has been demonstrated that basic amino acids, the chemical constituents of the proteins used in all living organisms, can be synthesized from inorganic compounds under conditions that replicate those of the early Earth. It has been suggested that the first reproducing form was merely some of the abundant amino acids grouped together in a shape against which others would chemically fit and then break away retaining the same or mirror image shape.
The first object that could self-replicate would likely not be anything that we would define as "life" by today's standards. Once there was an object from which copies naturally formed, the numbers soar. After 5 generations there would be 16 individuals. After 20 generations, half a million, and after 50 generations 500 trillion!
The first object that naturally produced copies probably was very poor at reproducing and may have been quite fragile. Being crudely formed, it may have taken hours to replicate or even years – but there was plenty of time. Within 100 generations, its descendants could probably reproduce in minutes.
From the beginning of the ability to replicate, changes began to occur. Then as now, there are occasionally errors in replication and most of the errors are harmful to the individual and/or the reproduction process. Those mutated forms were unlikely to reproduce. But every now and then a mutation is beneficial. It may cause the organism to be stronger, endure bumps (or other trauma) or to reproduce more quickly. These will quickly outnumber the rest of the population.
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There are a great many things that people have not discovered about the origin of life, but it is not reasonable to assume that magic was involved.
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