Why do scientists think the first living cells to appear on earth were probably anaerobic heterotrophs?

According to Miller Urey and Sagan, these cells were anaerobic because there was no oxygen in the atmosphere and they were heterotrophs, using fermentation as a process to obtain energy from the molecules formed by the heat and light in the early atmosphere. During the Archaea period, 3.4 billion years ago, after amino acids developed, the first living cells, the prokaryotes, with no nuclei, simple design, and no organelles

Scientists believe the first living cells on Earth were likely anaerobic heterotrophs because the early Earth lacked oxygen, and anaerobic organisms can survive and reproduce without oxygen. Additionally, heterotrophs obtain their energy by consuming organic molecules produced by other organisms, which would have been abundant in the primordial environment.

Scientists think that the first living cells to appear on Earth were probably anaerobic heterotrophs because early Earth lacked oxygen in its atmosphere. Anaerobic organisms do not require oxygen for their metabolism, which would have been advantageous in an environment without atmospheric oxygen. Additionally, heterotrophic organisms obtain their energy by consuming organic molecules produced by other organisms or from the environment, which would have been more accessible and abundant on early Earth compared to autotrophic processes. Therefore, anaerobic heterotrophs are hypothesized to have been the first life forms to emerge and thrive under these conditions.