One of the observations that led to people to think that life could arise from nonliving things was that

The correct answer is fish appeared in ponds that had been dry the previous season

This is according to the spontaneous generation idea which is opposite of the biogenesis idea which states that all living things come from other living things. The idea of spontaneous generation is mostly obsolete nowadays and no serious scientist has adopted the idea of it since the middle of the 19th century due to evidence of biogenesis.