The experiment conducted by Miller and Urey can be considered to be an evidence of sorts for this.

They took molecules which were believed to represent the major components of the early Earths atmosphere and put them into a closed system. The gases they used were methane (CH4), ammonia (NH3), hydrogen (H2), and water (H2O). Next, they ran a continuous electric current through the system, to simulate lightning storms believed to be common on the early earth. At the end of one week, they observed that as much as 10-15% of the carbon was now in the form of organic compounds. Two percent of the carbon had formed some of the amino acids which are used to make proteins.

Perhaps most importantly, this experiment showed that organic compounds such as amino acids, which are essential to cellular life, could be made easily under the conditions that scientists believed to be present on the early earth.