The assumption that aliens might resemble humans or animals can be attributed to the phenomenon known as anthropomorphism, which is the tendency of humans to ascribe human-like characteristics and traits to non-human entities. It is a natural cognitive bias, as our primary frame of reference is our own species and the living beings we encounter on Earth. When imagining extraterrestrial life, people often default to familiar forms and structures that they have seen or experienced before.
However, it's essential to recognize that the vastness of the universe and the diversity of environments it encompasses make it highly unlikely that extraterrestrial life would be exactly like humans or Earthly animals. The conditions and evolutionary histories on other planets or celestial bodies are likely to be vastly different, leading to potentially unfamiliar and alien life forms.
There are several reasons to believe that extraterrestrial life might be fundamentally different from life on Earth:
Diverse Environments: There are a wide variety of environments in the universe, ranging from scorching hot planets to icy moons and methane-rich atmospheres. Life in these environments would have evolved to adapt to their specific conditions, potentially leading to forms of life entirely unlike anything we know.
Biochemistry: Life on Earth is based on carbon, but there could be other plausible biochemistries that use different elements as the building blocks of life. Silicon, for example, is sometimes suggested as a possible alternative to carbon-based life.
Evolutionary Paths: The evolutionary history of an alien species would differ significantly from that of Earth. Different environmental pressures and circumstances would lead to the emergence of unique traits and adaptations.
Concealment: If advanced extraterrestrial civilizations exist, they might have evolved beyond the need for physical bodies or might choose to remain concealed, making it difficult for us to observe or detect them.
Evidence supporting the idea of diverse and non-human-like extraterrestrial life comes from astrobiology, which is the study of life in the universe. Despite the lack of direct evidence for alien life, scientists have discovered extremophiles on Earth—microorganisms that can survive in extreme conditions such as extreme heat, acidity, or pressure. This suggests that life may be more adaptable and diverse than previously imagined, increasing the potential for exotic life forms in the universe.
Additionally, the ongoing search for exoplanets (planets outside our solar system) has revealed a staggering number of potentially habitable worlds, each with its own unique conditions, further hinting at the possibility of diverse life forms.
While we can't say for certain what extraterrestrial life looks like, the scientific consensus is that the universe is so vast and diverse that the likelihood of finding familiar human or animal-like forms of life is minimal. Instead, we should be open to the possibility of encountering life forms that are radically different from what we know on Earth.