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What Was the First Life on Earth? A Self-replicating Molecule
The first life on earth, the first self-replicating molecule, originated in one of two ways:
- In situ hypothesis. Pre-biotic chemists believe life originated in the chemical cauldron that was the earth’s surface several billion years ago.
- Molecular panspermia hypothesis. In this hypothesis, organic molecules may not have had an earthly origin. On more than one occasion, astronomers have observed “sugar clouds” floating around in the Milky Way—some of the same non-living organic material contained in comets that smash into the earth every so often (not too often!). If this is how life on earth got kick started nearly 4 billion years ago, it probably happened on countless other planets in our galaxy and other galaxies.
How did non-life turn into life?
In popular mythology, life begins with “ensoulment,” which occurs at the “moment of conception.” In fact, there’s no such thing as a 'moment of conception.' The biological process of conception takes up to 48 hours to complete. Similarly, no sharp demarcation exists between non-life and life. Viruses, for example, have either DNA or RNA, but are not considered to be “alive” until they infect host cells, where they replicate and behave like life forms, sort of.