"In the beginning God created the heavens and the Earth. And the Earth was without form and void. And darkness was on the face of the deep. And the Spirit of God moved on the face of the waters."
This is how the Bible describes the beginning of the world. For a long time that, and other creation myths, were the best explanations we had. For the subject of the beginning of life was the airy concern of philosophers and theologians. Scientists didn't have much to go on.
The earliest fossils on Earth, clumps of bacteria called stromatolites, are found in Western Australia, and are 3.5 billion years old. They might be simple compared to life now, but single-celled bacteria have a cell membrane, allowing them to regulate their internal environment and metabolize chemicals to gain energy.