Is the Life on earth somewhat unique? Or, if we could somehow find life on other celestial bodies, they would be so radically different that we won’t even recognize them?
In this article, a scientist proposes that “If the history of life on Earth could be rewound and replayed, many of the same innovations would reappear, although at different times and in slightly different forms.”
I don’t have any sufficient reason to disagree with him, but I somehow cannot digest his hypothesis. I believe that Earth’s environment had played significant role in guiding evolution here. Moreover, evolution is susceptible to environmental catastrophes leading to mass-extinctions.
Let us imagine life on planet X. Let us say that the average temperature at X is -10 centigrades and it is lacking phosphorus (very unlikely, but remember that we are just imagining). Now, leave alone complex traits such as multi-cellularity, even DNA, Proteins, etc. are unlikely to evolve. They life at planet X could be significantly different in respects such as source of energy, metabolism…. Wild things such as gaseous life (I don’t know what that means), direct metabolism of EM radiation, distributed organisms, etc, could evolve there.
We don’t know much about universe, hence we must not generalize the nature of evolution in the universe. Unlike gravitation, there are no mathematical equations guiding evolution. Hence we cannot expect evolution to be predictable.