Not necessarily. There is current active research looking for non-DNA-based microbial life here on Earth, assumedly left over from Earth's formative years. The idea that we've never seen evidence of it is that it would have slipped right through the cracks of all our current tests - whether that means not detected or merely not differentiated.Moridin said:It is, at its core, a probability argument.
There is currently no concrete evidence to suggest that life has occurred more than once on earth. However, scientists have discovered microfossils that could potentially be evidence of life forms on earth as early as 3.5 billion years ago, indicating that life may have emerged multiple times in earth's history.
There are several factors that contribute to the possibility of life being a one-time event on earth. These include the unique conditions of our planet, such as its distance from the sun, its atmosphere, and its abundance of liquid water. Additionally, the timing of events such as the formation of the moon and the bombardment of meteorites may have played a role in creating the conditions necessary for life to emerge.
It is highly possible that life exists on other planets or in other parts of our own solar system. In recent years, scientists have discovered evidence of water on Mars and the potential for liquid oceans under the icy surfaces of moons like Europa and Enceladus. Additionally, the discovery of exoplanets (planets outside our solar system) in habitable zones further increases the likelihood of life existing elsewhere in the universe.
The theory of evolution supports the idea of life being a one-time event on earth. It suggests that all living organisms on earth share a common ancestor, and that the diversity of life we see today arose through a gradual process of natural selection and adaptation. If life had emerged more than once on earth, we would expect to see multiple, distinct lineages of organisms rather than a single interconnected tree of life.
If life on earth is a one-time event, it would suggest that the conditions necessary for life to emerge are extremely rare and specific. This could have significant implications for our understanding of the origins of life and the search for life on other planets. It could also raise questions about the uniqueness and fragility of life on earth and our responsibility to protect it.