Recently I dodged a bullet in avoiding the latest alien invasion movie. My friends who saw it, hated it. Bad ending and bad premise.
I can think of very few reasons why an alien race would invade the Earth. First, however, let’s discuss reasons they wouldn’t.
Humans as a reproductive medium
If an alien species requires a human body (or part of it) to procreate, how did said species exist and thrive to the point where it possessed the capabilities of interstellar travel?
Humans as food
If people made good food, cannibalism would have been more rampant. As convenience goes, there are far easier fish to fry (sometimes literally). No culture has ever developed on this planet that subsisted primarily on the flesh of people. Meat is more plentiful on things like cows. Chickens are far more efficient at converting vegetable matter to meat. And if you kill a cow or chicken, the other cows and chickens are highly unlikely to organize and fight back.
Humans as anything else the invading species needs
Humans evolved on Earth. Despite the claims of Creationists and ancient astronaut enthusiasts like Erich von Däniken, there is no “missing link” and humans were not created by the intervention of aliens or gods. That pretty much means that humans exist only on Earth. Nothing could exist elsewhere in the universe that depends on something only humans can provide.
Earth as a new home
I know we’ve only found under a thousand other planets so far. And so far, only a very few have been in the “Goldilocks Zone.” The key phrase in both of those sentences is “so far”. We know our technology is insufficient to find Earth sized planets. The wobble detection method, which most exoplanet discoveries have used, has previously required a planet bigger than Jupiter orbiting closer to its star than Earth is to our sun. As the various techniques to detect exoplanets mature, we are finding smaller planets farther from their stars. My opinion is that the trend is leading to a realization that every star has a planetary system of some kind. Earth is not unique, but the rarity is yet to be determined. Even if only 1% of stars have habitable planets, there are a ton of habitable planets out there. No reason to pick Earth. It’s not worth the fight. At the technological point where our weaponry is ineffectual, an alien race would possess the technology to terraform.
Earth as a mining resource
There’s nothing on Earth that isn’t somewhere else. Looking for Gold? Mercury has more gold per cubic meter than Earth. The science of planet formation tells us that the denser elements are going to stay closer to the star. Inner planets are going to be made of denser stuff – more metal, less gas. Aliens that have got interstellar travel down can handle mining from the dark side of Mercury. Seems an even more obvious place to look would be one of the hot “Superearths” we’ve discovered.
Which brings us to what threats we might face:
Humans make decent slaves. Though we are prone to periodic uprisings.
There is no hard and fast rule that says that technologically advanced races must be peaceful. We like to think that higher reasoning skills would teach that violence is not the answer, but we might be the America’s to some Centauri civilization’s Europe. If there’s a planet at Alpha Centauri and if it developed an intelligent species and if that species developed space travel a century or so ago, they could be sending billions of space marines as we speak. Some leaders measure their success by the size of their empire. If we’re the next planet outside their borders. Even if conquered, life will likely change little or maybe they’ll enslave us all to build for their war machine. But the technology window for this is small, once a civilization breaks certain technological barriers, the need for conquest vanishes. Peaceful trade is only slightly less profitable and a whole lot less stressful. And there is always the possibility of a species reaching a high technological level and not only plateauing but regressing much as Europe did after the fall of Rome.
The Predator series is not unfathomable. Of course, finding a human worthy of a trophy hunt is not easy. Convincing your friends that the trophy was a military commando and wasn’t just some farmland hick you beamed up off a country road in the middle of Nebraska might be tough.
Talking about alien life, I feel compelled to give the Fermi Paradox a mention. It’s the concept that, statistically speaking, other intelligent life must exist in the universe, but questioning why haven’t we made contact yet. I don’t see the paradox, really. Sure, I think there’s intelligent alien life somewhere. There are many reasons why we wouldn’t have contact with them. First, to quote Douglas Adams, “Space is Big.” There is a distinct possibility that Faster-Than-Light travel is impossible. Even if some warp technology is found, there’s not much interesting about our solar system to draw attention. Radio and Television signals will become gibberish and after a few light years are indistinguishable from the universal background radiation. The few space probes we sent out of the solar system are very small and unlikely to slam into anyone’s spacebus anytime soon.
It’s unlikely, but we might just be the most advanced civilization in the universe. It does take billions of years to create the elements, like iron, in the bellies of stars and via supernova explode them out into the universe. All the stars we see are made up of bits exploded from other long dead stars that were made up of bits of other exploded dead stars. It took 5 billion years, after the formation of the Sun and the Earth, for life to get where it could create a spaceship. And we only had one branch of the evolutionary tree make it to our level of intelligence. If early humans hadn’t crossed the land bridge or sailed across the oceans, the America’s would be devoid of intelligent life. Basically, this tells us that there could be planets out there with full biospheres of life without a single intelligent species. Intelligent life might be just that rare.
But if it does exist, it wouldn’t come to Earth to use our brains as incubators or attempt to conquer Earth if they are all violently allergic to dihydrogen monoxide.
Douglas Adams also had this to say on the subject:
It is known that there is an infinite number of worlds, simply because there is an infinite amount of space for them to be in. However, not every one of them is inhabited. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds, so the average population of all the planets in the universe can be said to be zero. From this it follows that the population of the universe is also zero, and that any people you may meet from time to time are merely the product of a deranged imagination.
-Douglas Adams (1952 – 2001), Hitchhiker’s Guide series