Here's the (excessively long) scenario:
The xenomorphs are pretty similar to us. They're made of carbohydrates, proteins, lipids, and water, they breathe oxygen and exhale carbon dioxide. Their genetic information is carried in DNA and expressed through RNA. Good stuff--this is all like a basic life-kit of really simple chemicals that are really good at expressing complexity when they're stirred around in the same soup. They prefer temperate climes that hover between the freezing and boiling points of water, because liquid water is awesome. They're even keen on Earth-style gravity because that keeps all their air and water from whooshing away into space.
Not only are those basic building blocks the same, but they're bipedal, having evolved from quadrupeds because quadrupeds are parsimonious, and they need their hands in order to use tools. Bilateral symmetry, erect posture, opposable thumbs, internal lungs and other dry land accoutrements (they're land-dwellers . . . figure that if you're going to take advantage of basic technologies like fire, you've probably evolved to be a land-dweller) and basically they are your standard rubber-forehead-alien. Maybe with a little light variation . . . some scales, say, or retinas right-side out, or separate orifices for breathing and eating. They see using light and hear using sound because those are both relevantly scaled modalities useful throughout the course of evolution. They're even roughly our size.
So these guys could basically be our long-lost cousin space-apes. And they have a civilization that ultimately results in space travel, 'cuz if they can't cruise space, we're really not interested. This civilization is basically the same as the one we'll eventually end up with because game theory, like physics, chemistry, and evolution, follows a universal set of rules.
Now . . . some differences. Though they have DNA and RNA, obviously their genomes are completely different than ours. Anything that can be arbitrary (restriction sequences, promoter regions, etc.) is completely different unless there's some kinetic reason for it not to be. Chromosome number, you name it. The short story is that they're not interested in our women.
Likewise, though they have a craving for energy-packed protein-rich flesh and their genetic code comprises a library of amino acids assigned to three-base codons (two means only sixteen amino acids, minus STOP codons, and four would be 256, which is way more than is probably necessary) the more complicated amino acids are different, and even the simple ones have a different chirality. They don't have the biochemistries to deal with the terrestrial complement of proteins. Eating human flesh makes them nauseous and gives them diarrhea. They're totally not interested in chowing down on us, our cats, or even our crops.
Their own proteins, based on a differing complement of amino acids, bear little or no relationship to our own except where form follows function--and even here, since the forms are made of different building blocks, they're incompatible. Think linux and windows, but less compatible. For them, there's no compelling commercial interest in taking tissue samples or probing us. Also, we smell funny.
They've evolved on a world with a seventeen hour light-dark cycle. Even hanging out on Earth gives them chronic jet-lag and makes them grumpy and depressed . . . and to add insult to injury, even though they're bona-fide oxygen breathers and carbohydrate metabolizers, their regulatory systems are calibrated to a partial pressure of oxygen outside their comfortable range of adaptation, making them giddy or causing them to pass out after just a few minutes in our air. Their food crops really suck it up . . . soil nutrients are all wrong, the bacteria just aren't right, the photoperiod and season lengths are uncomfortable, and they're just not equipped to handle the spectrum of light our sun puts out. So these aliens really are not all that keen on vacationing here, much less moving in to stay.
This basic incompatibility also makes us lousy slaves. If they want us to grub around in their spice mines back home, they have to raise our kind of food and one little breach in the mine's Earth-air-type seal and oops . . . gotta import more of us from halfway across the galaxy. They also have to go through the hassle of learning our language if they want us to work efficiently. It's just so much easier and cost-effective to make slaves of your own species.
As for the resources buried in Earth's crust. If there's one thing any canny space-faring species can use, it's more basic elements to fuel their chemical and metallurgical industries. Except that, as has been pointed out several times in this thread, all that crap's floating around in space for the taking, along with more solar power than you can shake a stick at. You don't have to waste energy boosting it into orbit or trucking it home halfway across the galaxy to a place where the climate's more hospitable.
. . . and you really don't have to quarrel with natives over it. Space is huge! We're pretty unlikely to run out of it before the next Big Bang. You have to go out of your way to even be likely to randomly bump into someone else, much less find that the one thing you need more than anything is only found on their home planet under their big tree . . . much less exert the effort involved in genocide . . .
Speaking of which, space is huge! Complete genocide's a pretty tough job, what with having to scrub out every individual likely to hold a grudge, and the fact is that once interstellar travel is in-play, every dude with a decent fusion-or-whatever-powered rig has Armageddon at the press of a button. Do-it-yourself Rods from God, near-C collisions, a meltdown of whatever immense power source allows you to jet around from star-to-star . . . why risk it?
So . . . in summary, interstellar conflict between us and this hypothetical species is:
a.) pointless
b.) possibly dangerous
. . . and if they're smart enough to come visit, they know it.
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Topic: Stephen Hawking is afraid of aliens (Read 18850 times)