Predicting what extra-terrestrials will be like: and preparing for the worst

Abstract

It is difficult to imagine evolution in alien biospheres operating in any manner other than Darwinian. Yet, it is also widely assumed that alien life-forms will be just that: strange, un-nerving and probably repulsive. There are two reasons for this view. First, it is assumed that the range of habitable environments available to extra-terrestrial life is far wider than on Earth. I suggest, however, that terrestrial life is close to the physical and chemical limits of life anywhere. Second, it is a neo-Darwinian orthodoxy that evolution lacks predictability; imagining what extra-terrestrial life would look like in any detail is a futile exercise. To the contrary, I suggest that the outcomes of evolution are remarkably predictable. This, however, leads us to consider two opposites, both of which should make our blood run cold. The first, and actually extremely unlikely, is that alien biospheres will be strikingly similar to our terrestrial equivalent and that in such biospheres intelligence will inevitably emerge. The reasons for this revolve around the ubiquity of evolutionary convergence, the determinate structure of the Tree of Life and molecular inherency. But if something like a human is an inevitability, why do I also claim that the first possibility is 'extremely unlikely' ? Simply because the other possibility is actually the correct answer. Paradoxically, we and our biosphere are completely alone. So which is worse? Meeting ourselves or meeting nobody?

The detection of extra-terrestrial life and the consequences for science and society

“…Therefore, a widely adopted strategy is to search for liquid-water habitats, given that terrestrial biochemistry relies on liquid water as solvent (cf. [16,27]). Moreover, given the requirements of metabolism, energy is a more universal imperative for life, providing a further criterion to narrow down searches, and opening an opportunity to go far beyond characteristics that might be specific to life as we know it [37].…”

“…Strikingly, a system of life based on molecules just of opposite chirality but otherwise identical to those that form the building blocks for life known on Earth appears to be a viable distinctive alternative (cf. [16,17,27]). …”

“…The latter is strongly supported by the observed evolutionary convergence in the biological history on Earth, but it cannot be ruled out with certainty that our existence is a fluke arising from a highly improbable chance event (cf. [27]). …”

“…[27]). However, with the Sun just about half-way through its lifetime as a main-sequence star, with about 4.5 billion years remaining, that 'comparable stage' might constitute a rather short transient episode, and advanced extra-terrestrial life might be inconceivable to us in its complexity, just as human life is to amoebae.…”

‘Grandeur in this view of life’:N-body simulation models of the Galactic habitable zone

“…Such a fair biosphere is less likely to produce a complex intelligent species, detectable via interstellar travel, distant communication and other means, such as IR excess from dissipated energy (Zackrisson et al, 2015). There are multiple reasons to believe that evolution of cognition and intelligence is possible only within a large and diverse habitats, where many necessary evolutionary innovations could be achieved (Russell, 1995;Vermeij, 2006;Morris, 2011). It is unlikely to happen in tightly constrained, ultra-specialized habitats.…”