Why Can't Alien Life Be Non-DNA-Based?

It is certainly possible that alien life forms could exist without a DNA-based structure. These extraterrestrial entities are not constrained by our biological norms and could develop entirely different physical and chemical characteristics.

The Possibilities of Non-DNA-Based Life

Life, as we know it on Earth, has commonalities due to its shared ancestor. These commonalities have helped scientists understand evolution. However, this does not necessarily mean that all forms of life must adhere to the same rules.

André Brin, a science fiction writer, explored this concept in his Uplift series, where he introduced planets with life forms that originated from five independent evolutionary paths. Local scientists on these planets deduced that there must have been at least five distinct origins for life. This suggests that non-DNA-based life could be a valid possibility.

Beyond DNA: Early Life and Chemical Complexity

Some forms of life may not have relied on DNA to store genetic information at the beginning. DNAt might have been an evolutionary addition as cellular complexity increased. However, once DNA was formed, it might have become the dominant medium for storing genetic information due to its compactness and efficiency.

It is conceivable, though unlikely, that alternative chemical entities could serve the same function as DNA. Any chemical that can compactly store a vast library of genetic information and be equally efficient in translation would be a viable candidate. However, the process of unwinding and separating complementary strands, as required for protein synthesis, would still pose a significant challenge.

The Universality of DNA

On Earth, once DNA evolved, it has likely become the primary medium for cellular reproduction, outcompeting other potential information storage molecules. If we consider the vastness of the universe, it is reasonable to hypothesize that DNA-like molecules might be uniquely suited for compact information storage and translation in environments with similar conditions.

However, it is also possible that extraterrestrial life might have developed entirely different storage mechanisms, given the vastness of the universe and the many potential scenarios for life to thrive. Sci-fi writers have already explored the possibilities of energy beings, silicon-based life, and more. It is entirely plausible that something similar might exist elsewhere in the cosmos.

Until we find evidence of extraterrestrial life, all we can do is imagine. The basic unit of life on Earth is known as the cell, but other species or forms of life might have a different fundamental unit. Until we discover them and study their biology, we must remain open to the myriad possibilities that the universe might hold.