"We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet," he said. "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 colonize whatever planets they can reach. If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans."
To me, this reads as sensationalist nonsense. As brilliant as Hawking is, he's talking out of his field. Hawking is a a physicist, not an anthropologist or an historian or even a biologist or anything else that imply any kind of knowledge whatsoever about what an alien civilization might develop into. Even so, Hawking's position is based upon three flawed assumptions:
- That intelligent life elsewhere in the universe will have biology compatible with our ecosystem.
- That Earth has resources that can't be found elsewhere. Even in our own star system, basic elements such as water and other resources are available in places where it would be much easier to harvest them. It would be easier to farm their own (or our) asteroid belt and Oort cloud for natural elements.
- That an intelligent species capable of traveling between stars would find it more expedient to enslave/exterminate the rare pocket of intelligent life they come across rather than solve their resource problems technologically. If you have the technology and the energy to traverse the gulf between stars, why aren't you smart enough to solve your resource problems?
Hawking's statement seems to be in direct opposition to what Carl Sagan once said. Sagan believed that advanced beings couldn't logically want to harm us, given that they'd obviously avoided killing themselves to progress to the point that they've attained space travel. I'd prefer that belief to one where intelligent life is either malevolent or indifferent to us. However, Sagan was no more or less qualified to comment on the issue than Hawking is.
Personally, I think that, if we meet intelligent life, we need to treat them with respect, not fear. After all, they've probably already been here anyway and have just been waiting for us to mature.