The Dangerous Neighbors Hypothesis suggests that intelligence may be common but that communicative intelligence is rare. The reason for this is that those species that do communicate their presence tend to be obliterated by their neighbors, leaving only those species that maintain a strict cosmic silence alive. Charles Pellegrino, in particular, has come up with "The Three Laws of Alien Behavior", which he contends apply to all species:
- Their survival will be more important than our own survival. If an alien species has to choose between us and them, they won't choose us. It is difficult to imagine a contrary case; species don't survive by being self-sacrificing.
- Wimps don't become top dogs. No species makes it to the top by being passive. The species in charge of any given planet will be intelligent, alert, aggressive, and ruthless when necessary.
- They will assume that the first two laws apply to us.
The rationale is that, in recognizing that other species represent a potential threat, and given that the survival of one's own species is of primary important, the most rational thing to do when encountering another species is to destroy them before their potential threat is transformed into a real threat. In the meanwhile, because you can assume that other species will do the same to you, your best option is to remain absolutely inconspicuous (e.g., no open radio broadcasts).
There are two major objections to the DNH. The first is to argue that it is presumptuous to simply assume that all other species will be automatically aggressive to the point of acting with paranoid abandon. Supporters of the DNH note that even if we do presume that some species are altruistic, such species will still be in jeopardy from species that embrace the rationale of the DNH. Over time, a sort of cosmic natural selection would weed out the altruistic species leaving a galaxy full of dangerous neighbors.
The second objection is to question the technological feasibility of destroying another species in a first strike, particularly without opening oneself to a counterstrike. Unfortunately, this is a very technical topic and it would be impossible for me to give a fair representation to the points and counterpoints that have been made over this contention. Suffice it to say that both sides do have arguments for their respective positions.
As a final note, the DNH is, perhaps, the only solution to the Fermi Paradox that directly impacts upon our own survival as a species. If the DNH is true, our radio broadcasts are placing us in grave danger and should be curtailed as soon as possible.