Why We Haven't Encountered Intelligent Extraterrestrial Life

Life is a result of the process of evolution and, there being no reason to believe that the Earth is uniquely suited to hosting evolution, it seems reasonable to believe that life is common throughout the universe. The simplest hypothesis would suggest that, of the total star systems in the galaxy, some contain planets with the necessary ingredients and conditions to support life, and of those some have evolved life. Of those planets with life some have evolved forms highly organized into complex, technological cultures. By this logic something like the "Star Trek" universe (or galaxy) seems likely.

The puzzle is this: assuming that we live in a Star Trek universe, why haven't we been contacted or visited by other cultures?

Contrary to the Star Trek universe, the fastest feasible speed for interstellar travel may be limited to some small fraction of light speed. If this is the case then a typical journey between advanced cultures in different star systems might require times on the order of many lifetimes of the individuals.

Very long interstellar journeys would thus require the culture and the individuals comprising it to invest resources for the benefit of their descendants in the distant future, highly altruistic behavior. In fact, the existence of technology for interstellar travel implies a highly organized and highly cooperative culture, one in which a complex web of rules would be necessary to share benefits fairly thus ensuring cooperation. In our own history, as societies have become more complex and as individuals have become more specialized and therefore more dependent upon society, we have developed ever larger bodies of abstract rules embodied in religion, law, and ethics to provide incentives for cooperative behavior. The core and the source of this cultural system is our propensity towards altruism. Our culture is built upon and benefits from the philosophy of altruism and cooperation which is implemented by abstract rule systems. These rule systems seem to evolve towards increasing generality or 'universal-ness' so that our culture's altruistic impulse has even manifested itself as legal protection for other species and for the 'natural' environment.

As Earth culture is the only example we have at the moment, let us assume that other cultures would behave similarly to our own. Projecting our culture into the future or using these ideas to predict another advanced culture, it seems necessary that the achievement of interstellar travel would be accompanied by a high degree of altruistic behavior.

And this is where Star Trek-type ideas give us guidance. It may be that such advanced star-travelling cultures address other less-advanced cultures with a "do not interfere" or "do no harm" policy as in Star Trek. So it may be that other cultures are aware of the existence of our culture but have refrained from making contact out of a desire to protect us in some way.

PostScript: Apparently Daniel Dennett has advanced a similar idea about the development of what he calls "conscience" in humans. This excerpt from Wikipedia discusses his thinking:

In game theory terms, a free rider is an agent who draws benefits from a co-operative society without contributing. In a one-to-one situation, free riding can easily be discouraged by a tit-for-tat strategy. But in a larger-scale society, where contributions and benefits are pooled and shared, they can be incredibly difficult to shake off.

Imagine an elementary society of co-operative organisms. Co-operative agents interact with each other, each contributing resources and each drawing on the common good. Now imagine a rogue free rider, an agent who draws a favor ("you scratch my back") and later refuses to return it. The problem is that free riding is always going to be beneficial to individuals at cost to society. How can well-behaved co-operative agents avoid being cheated? Over many generations, one obvious solution is for co-operators to evolve the ability to spot potential free riders in advance and refuse to enter into reciprocal arrangements with them. Then, the canonical free rider response is to evolve a more convincing disguise, fooling co-operators into co-operating after all. This can lead to an evolutionary arms races, with ever-more-sophisticated disguises and ever-more-sophisticated detectors.

In this evolutionary arms race, how best might one convince comrades that one really is a genuine co-operator, not a free rider in disguise? One answer is by actually making oneself a genuine co-operator, by erecting psychological barriers to breaking promises, and by advertising this fact to everyone else. In other words, a good solution is for organisms to evolve things that everyone knows will force them to be co-operators - and to make it obvious that they've evolved these things. So evolution will produce organisms who are sincerely moral and who wear their hearts on their sleeves; in short, evolution will give rise to the phenomenon of conscience.

This theory, combined with ideas of kin selection and the one-to-one sharing of benefits, may explain how a blind and fundamentally selfish process can produce a genuinely non-cynical form of altruism that gives rise to the human conscience.