Paul Davies disagrees with Stephen Hawking:

When British cosmologist Stephen Hawking warned against contact with extraterrestrials in a new Discovery Channel documentary, … [his] comparisons with Columbus … reflect the rampant anthropocentrism that pervades much speculation about alien life.  Just because we go around wiping out our competitors doesn’t mean aliens would do the same. A civilization that has endured for millions of years would have overcome any aggressive tendencies, and may well have genetically engineered its species for harmonious living. Any truly bellicose alien species would either have wiped itself out long ago, or already taken over the galaxy.

By comparison, humans would quite likely be considered dangerous warmongers, posing a possible menace to our galactic neighbors in centuries to come. If so, then ET may act to eliminate the threat if we didn’t mend our violent ways. Ironically, the greatest danger from an alien encounter may be ourselves.

Many species here on Earth have endured for millions of years while retaining “aggressive” tendencies, and even very “mildly” bellicose aliens, ones who would only exterminate us if they could make a plausible case that we might pose a future menace, should still be of great concern to us.  I sure don’t want to be exterminated “just in case.”  Wouldn’t it make more sense then to shut up until either we don’t look so menacing, or until we are strong enough to defend ourselves?

If I didn’t know more about Paul Davies, I’d leave it at that.  But Davies has long been a well respected academic expert in this area, and I’ve come to respect him in my personal contacts.  I can’t claim he hasn’t heard contrary arguments; he invited me to present my “Burning the Cosmic Commons” work (more) at a workshop he held, and he covers it extensively in his (good) new book The Eerie Silence:

Hanson points out that whatever the motives a community may have for spreading, and whatever the parameters such as travel speed, length of sojourn at new colonies, order of priorities and level of incentive to continue, there will always be a fastest wave of of migration  Given a sufficiently rich plethora of diverse cultures vying for planetary pastures new, the leading edge of this wave will be determined purely by competitive selection effects.  [p127]

Davies even considers in great depth possible signatures that an alien colonization wave passed this way long ago:

How about this: aliens passed through our part of the galaxy a long time ago harvesting comets? … If the solar system is typical, and other stars have comet clouds too, then the comets ejected from them should sometimes come our way and enter the solar system.  If an extra solar comet paid us a visit, it would be seen traveling on a hyperbolic rather than elliptical orbit, i.e. moving too fast to be from the Oort cloud.  So far no such comet has been seen, which is a bit puzzling.  [p133] …

We can’t be sure the [puzzling] lack of monopoles is universal – maybe its just our region of the galaxy that is affected.  Are the aliens to blame?  Why would magnetic monopolies be of use to them?  Monopoles would be the power source of choice for any self-respecting super civilization. [p137]

But even though Davies accepts that selection could induce such rapacious alien expansion, he still sees any nearby aliens as unthreatening:

Obviously not every spacefaring civilization would choose to colonize the galaxy in a grand imperial manner; … But it only takes one such community somewhere in the galaxy to present us with Fermi’s awkward conundrum. [p120] … The motivations of intelligent aliens are a closed book to us.  Whatever might induce them to spread out, it is unlikely to be the product of primitive urges that confer little long-term survival value – the relevant genes would, I believe, long ago have been engineered out of the gene pool. [p125] … Once technology advance to the point where a community can exercise choice over who survives and who doesn’t, pure natural selection breaks down.  … The further course of evolution can be determined by design. [p154] … Free of primitive Darwinian urges such as flight-and-flight, disgust and the need for procreation, autonomous computers are unlikely to see humans as threatening or in competition with them. [p159] …

Can we trust ET not to dupe us?  An alien civilization might not be explicitly hostile to humans.  It could regard us as mildly useful, but ultimately ‘in the way’ and of little relevance to their grand scheme.  They might enlist our help, then elbow us aside. … An alien civilization that goes the the trouble and expense of actively trying to contact us would probably be highly altruistic. [p171]

The danger from METI is miniscule. …We need to ask why aliens would be interested in harming us or invading. … The greatest danger to humanity is if a nearby alien community judges us to be a threat.  Given our warlike history, that is not an unreasonable conclusion. …The aliens might decide to mount a preemptive strike for the greater good of the wider galactic community.  And could we blame them …? … But even if this gloomy assessment is correct, METI would not increase the risk of bringing fire and brimstone down upon us.  In fact it may serve a useful purpose if we could signal our best intentions to ET. …

I am in favor of METI, not just because I think there isn’t a snow-ball’s chance in hell of anyone out their picking up the signals, but because the act of designing and transmitting messages to the stars serves manny noble purposes, such as raising interest in science in general and SEIT in particular, and in encouraging people – especially young people – to think about the significance of humanity and the vastness of the universe, and to reflect on the common factors among our disparate cultures that we wish tho preserve for posterity. [p198]

Davies’ reasoning still puzzles me.  Why not just inspire youth by standing in a field and yelling up to the sky “Yo aliens, here we are!”?   OK, youth may not believe that aliens could hear you then.  And yes, if you tell kids you used a big expensive radio telescope to send a message, they’ll naturally assume you did that because you calculated aliens could hear you that way.  But if you actually calculate that aliens couldn’t possibly hear you that way, well then you are “inspiring” youth by lying to them. Why not “accidentally” leave your telescope unplugged, or just lie about having used it?  Would those lies be worse than tricking them into assuming your radio telescope could be heard?

But if your argument is that while the chance is small it is real, with a substantial expected value when you multiply the probability of contact times the value of such contact, well then you have to consider the relative probability and value of friendly versus hostile contact.  Sure we can’t assume they’d be hostile, but neither can we assume they’d be friendly.  Until we have a better handle on how to make this calculation, shouldn’t we just shut up in the meanwhile?