Would Life Really Develop Differently On Another Planet? The Convergent Evolution
An alien is about to open the door of his spaceship… What will it look like?
Pointed ears, blue skin, abnormal head, or reptilian jaws: there are a thousand ways in which science fiction literature, movies, and alleged eyewitness accounts have depicted Aliens visiting Earth. So different in height, shape, and somatic features, but still with one thing in common: a vaguely human appearance.
But if in the entertainment world, it is easier and cheaper to make up actors as humanoid E.T.’s rather than as shapeless blobs or tentacled octopuses–in the scientific debate the criteria are evidently different.
Yet there is no consensus among researchers as to what these possible neighbors from the next galaxy should look like: assuming and not assuming they exist, are they similar enough to us or so different that our minds cannot even imagine them?
Some argue that it is futile to speculate on the nature of alien life; our imaginations would be too constrained by our own experience to be able to embrace the amazing heterogeneity and unusual possibilities perhaps realized in other worlds.
Well, if I may express my personal opinion… I disagree.
In my opinion, science can help us overcome such a pessimistic view, allowing us to make realistic assumptions about how aliens might be structured morphologically.
Many – like me – are confident that the laws of physics and chemistry are unambiguous and universal. And that they work on Earth just as they do on any exoplanet.
If there is one thing we know for certain about aliens, it is this: they too, just like us, are a product of evolution by natural selection.
Others, however, believe that biology is an exception. They find it hard to believe that the biological laws underlying Earth’s evolution are also applicable to exoplanets.
Carl Sagan, one of the most famous astronomers of the twentieth century, was firmly convinced that intelligent life existed elsewhere in the universe, yet he wrote, “To our knowledge, however, biology is a literally terrestrial and provincial science, and we can be familiar with only one special case in a universe of diverse biologies.”
When we face the unknown, there are indeed good reasons to be cautious. But why should biology be “terrestrial and provincial” rather than universal? Shouldn’t the laws of nature, physical, chemical, and even biological, be common to the entire universe?
Fortunately, there is a strong component of scholars in the scientific community who do not think like Sagan. According to them, aliens, if they exist, cannot be so different from us–and to support this hypothesis they usually invoke a well-known phenomenon, that of evolutionary convergence.
Would Aliens Look Like Us?
This is why a mammal like a dolphin looks similar to a cartilaginous fish like a shark. Even a creature that developed and lived in the liquid ocean of a distant exoplanet would probably develop a fish-like shape to move quickly.
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