"We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet. I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise [Americans say sic] whatever planets they can reach."
So shut down SETI (Search for Extra-Terrestrial Intelligence)! Tone down the radio transmissions! And don't talk to strangers if they're short and green!
Hawking alludes to Columbus as an example of what space aliens might be like. But we've come a long ways from the Middle Ages, haven't we? Many of us? The Borg, the evil menace of the Star Trek TV series, may be the science-fiction stereotype (apparently modeled on the golden-age Hollywood motion picture studio) that Hawking suffered with a little too much. And no. I disagree. And I'm appalled. Who would have imagined a scientist in fear of the future, in fear of foreign scientists?
I'm not a scientist, but I'm inclined to optimism, to faith in creature-kind - at least in the kind of creatures who can advance so far as to master interplanetary travel. I will concede that much like global-warming denial, the risk factor alone argues for prudence as the better part - if I'm wrong, advertising ourselves to the universe with radio signals is a very bad idea.
But an extra-terrestrial civilization with massive ships capable of interstellar travel will be able to find us no matter what we do. They'll have it all down. And rather than relying on a strategy of sitting back and waiting for naive attempts at friendly communication from relatively advanced planets, they will be out scouting smartly for primitive and pristine planets with untapped resources. And if it's meat they're after, we flatter ourselves to think we're a desirable catch. Think about it: Two-legged creatures (only two drumsticks!) high in fat content, pre-marinated in chemical poisons, and intelligent enough to know, and raise hell, when we've been fenced in a feedlot. I'd pass if I were an extra-terrestrial. For every world like ours there must be a hundred that are teeming with herds of leaf-eaters.
So maybe there's an extra-terrestrial civilization that just plunders whatever it comes across. The question is: Is an inter-galactic Columbus a realistic possibility? What sort of society can achieve, and sustain, advanced technological development without first destroying itself with nuclear weapons, without the political virtues of greed and power-lust collapsing its entire eco-system?
Consider our own social models of potential galactic expansion before pre-judging the likely character of space visitors. China looks to be the next society to emerge supreme on our world, just based on current momentum. It's not a pleasant prospect, if the space-aliens who come to visit have followed a Chinese-like model. They'll eat anything in China, from yellow-mellow insect innards to cute little kittens; a "Red Chinese" style space invasion by huge, highly weaponized, and voracious meat-eaters would be a terrifying prospect. But how long can China keep a lid on a billion-plus people being treated like ant-workers? How far can they progress, how creative can their best repressed-and-blindered minds ever be, to develop beyond the level of catch-up by pirating others' technology, when there's no more technology to pirate? The Chinese have been building empires of warlords upon regional warlords for millennia. Each time a new dynasty is consolidated the warlord structure begins to fracture again. Historically, the Chinese could never extend their empires beyond the sea, so how could such a system reach across solar systems? It's an extremely unlikely model upon which to build a successful interstellar operation.
Would our extra-terrestrial visitors come from a U.S.-style system of corporate-and-government consolidation and domination? Forget about it. The ideology of the quarterly bottom-line, mega-merger, bonus-bonanza, lobby-horsing, peon-pinching, and divide-and-bonker is too ridiculous to keep from imploding on itself long before it could embark on interstellar exploration. Oh wait - it's already imploding.
European social welfare? If you can overcome the way that word "socialism" makes you foam and drool with rabid salivation, it begins to seem plausible: A society that puts the general welfare above all else, that respects or at least tolerates individual eccentricity, provides free education - even higher education - celebrates the arts, humanities, and vacationing, and willingly pays even its technological workforce a living wage.... It could work!
Look at our history as a species. Along with technological development there has always been cultural and philosophical development. Sometimes technology outpaces culture, but neither leaves the other far behind. Our planetary culture has tended toward an ever-greater appreciation for the intrinsic value of sentient beings - all sentient beings. More and more humans qualify as humans. More and more animals qualify as pets. More and more people are rejecting cannibalism, human sacrifice, slavery, and discrimination. More and more people are refusing to eat anything with a brain. It seems to be a development that has paralleled, more or less, our development of technology.
I believe it's a universal truth: Civilizations either develop culturally as they develop technologically or they collapse dinosaurically. So I believe extra-terrestrials are going to be nice. And I'm willing to risk it, too. When other earthlings are quaking in their homes, refusing to come out and talk, I'll stand forward, I'll put myself between the little greens and the Steven Hawkings. I'll put my hunch and my life on the line. Give me a Hawaiian lei, a book of world history (one that precedes the Texas school board's authority), and a Chinese kitten (just for test purposes). Then take me to their leader!