2001 02 22 Nature - Vol 409 - Jack Cohen

Magazine Overview

This issue of Nature features an "insight commentary" titled "Where are the dolphins?" by Jack Cohen and Ian Stewart, published on February 22, 2001. The article delves into the complexities of searching for extraterrestrial intelligent life, moving beyond the assumption of Earth-like beings to consider a broader definition of "alien" and the concept of "xenobiology."

The Search for Extraterrestrial Life Beyond Earth-like Forms

The authors begin by acknowledging the current scientific focus on finding extrasolar planets similar to Earth, but they question this narrow approach. They highlight the prospects for Earth-like aliens due to the prevalence of similar cosmic environments, citing the potential for oceans beneath Europa's icy surface as an example. However, they emphasize that the true meaning of "alien" implies beings very different from ourselves, potentially inhabiting environments unsuitable for Earth life. They posit that some of these aliens might be intelligent and possess advanced technology, including interstellar capabilities.

The central question posed is "Where are the dolphins?" – a metaphor for intelligent, non-humanoid aliens. This leads to a discussion of Enrico Fermi's paradox: if intelligent aliens exist, why aren't they here?

Canonical Answers to Fermi's Paradox

• The article lists several common explanations for the absence of aliens:
• No Aliens: Humanity is unique.
• Self-Destruction: Advanced civilizations destroy themselves, often through nuclear war.
• Short Lifespans: Civilizations exist but not concurrently with our own.
• Impossibility of Interstellar Travel: Relativistic limits or the inability of living creatures to survive such journeys.
• Lack of Interest: Aliens exist but are not interested in interstellar travel or contact.
• Galactic Law: Contact is forbidden due to humanity's perceived primitiveness or violence.
• Elimination: Some aliens actively eliminate other technological civilizations.
• Already Here: Aliens are present but undetected (a popular internet theory).

The authors note that evidence for these assertions is generally poor, citing the unconvincing nature of eyewitness abduction accounts.

Xenobiology: A Broader Perspective

The discussion area is termed "xenobiology," which the authors prefer over "astrobiology" because it focuses on the biology of the strange and extends contemporary biology into new realms. They argue that science should not be constrained by current understanding, using the example of physics a century ago to illustrate how scientific paradigms shift. Xenobiology requires contemplating what *might* happen, not just what *does* happen, and involves exploring "xenospace" – the vast realm of possible aliens, their evolutions, and cultures.

The Nature of Life and Universals vs. Parochials

Life is described as an emergent phenomenon that the Universe "invented." The authors suggest that the diversity of life is far greater than currently realized, and that Earth's life-forms, while diverse, may share certain "universal" features rather than "parochial" ones. Universals are traits that arose independently more than once in evolution (e.g., flight, photosynthesis), while parochials are unique to a specific lineage (e.g., pentadactyl limbs). Alien evolution will mirror Earth's in universals but differ in parochials.

They challenge the idea that DNA, carbon-based molecules, or an oxygen/water environment are necessarily universal. Instead, they propose that the dual interpretation of DNA as "instructions" and "information" (predicted by von Neumann) is likely a universal principle, suggesting that aliens will have their own form of genetics, possibly based on different substrates.

Extelligence: The Key to Advanced Civilizations

A crucial concept introduced is "extelligence," which is presented as more important than mere intelligence for sentient, technically competent aliens. Extelligence is the contextual analogue of individual intelligence, encompassing language, permanent archives, and communication technologies. It is this extelligence that has driven human cultural growth and technology. While human intelligence is only marginally greater than that of chimpanzees, our collective extelligence is far more powerful.

The authors consider whether intelligence and extelligence are universals or parochials. While intelligence has arisen only once on Earth, its presence in various species suggests it might be a universal. Extelligence, however, appears to be a parochial trait. They note that dolphins, while communicative, show no signs of technology, suggesting a potential deficiency in extelligence, though they concede that dolphin technology might simply be too alien to recognize.

Habitats and the Unseen Alien

Life, being a universal, can evolve in any habitat that supports the necessary complexity of organization, not just Earth-like water/oxygen planets. Science fiction has explored numerous exotic habitats, from gas giant atmospheres to stellar interiors. The authors propose that aliens might not wish to visit Earth, just as humans would find many alien environments unattractive. They suggest that aliens might be observing us for scientific purposes, leaving subtle clues in their "xenobiology texts."

If aliens are present, they would likely be undetectable due to their advanced technology, which Arthur C. Clarke famously described as indistinguishable from magic. They might not resemble "Little Green Men" but could look like people, animals, or even be invisible, existing in dimensions or states beyond our perception.

The Introspective Trend and Humanity's Reluctance to Explore Space

The article concludes by reflecting on humanity's own "introspective trend." Despite landing on the Moon decades ago, the capability for manned lunar missions has been lost. Plans for future space exploration, such as manned missions to Mars or probes to Pluto, face cancellation or lack of enthusiasm. The authors pose a final, poignant question: is the inability or reluctance of an extelligent species to leave its home planet a universal trait? They suggest that the most likely reason for the absence of aliens is not their non-existence, but rather their "alien extelligence" – the realization that virtual experiences might be preferable to the expense, risk, and potential boredom of actual travel.

Recurring Themes and Editorial Stance

The commentary consistently challenges anthropocentric views of life and intelligence. It advocates for a broader, more imaginative approach to xenobiology, emphasizing the potential for life to exist in diverse forms and habitats. The authors express a skeptical but open-minded stance on the existence of extraterrestrial intelligence, leaning towards the idea that their absence might be due to their own advanced understanding and priorities (extelligence) rather than a lack of existence or capability. The article also subtly critiques humanity's own limited ambition in space exploration, suggesting it might be a universal characteristic of advanced, introspective species.