Humans apparently got the short end of the evolutionary stick. All aliens can easily shapechange or invade our bodies, and thereby infiltrate our society because they, for some reason, desire our planet. Or our women.
Dangerous true, but I thought it was just edged out by “Derelict Spaceship Salvager”.
http://www.orionsarm.com/topics/space_hulks.html
And even that might not help . . .
In the near future, astronauts will fly in business suits! (Gattaca.)
This theme might be prevalent in science fiction, but if we substitute “enslave you” for “eat you,” it is eerily reminiscent of what the New World natives experienced when meeting the Spaniards. So maybe there’s something to it.
Sailboat
SF?! Heck, I learned that from Beowulf! 
. . . And some few of the Spaniards got eaten by the natives, too.
Never build Toasters or other AI constructs without at least building in a Silicon Heaven Belief Chip…
Or our men. Perhaps both. We are in the Alpha Quadrant
In the near future, mankind will forget what a fuse is.
Alien contact in science fiction has been portrayed as parallel to European contact with indigenous people all the way back to War of the Worlds in 1898.
They will also forget some basic, common-sense workplace safety practices, such as seatbelts, having the crew sit down when there is a high likelihood of something shaking the ship and throwing everyone around, or putting railings around holes in the deck.
Why did the Death Star need those holes in areas where the crew would be, anyway? Their workers’ comp insurance rates must be astronomical.
But that was a long time ago and in a Galaxy far away.
Besides it looked life was pretty cheap in the Empire. 
Jim
I’d think replacing a cloned stormtrooper would be a lot more of a pain than replacing a normal crewmember on a spaceship. Unless they have huge numbers of clones in reserve somewhere (expensive), they’d have to create a new clone and raise it until it was old enough to be a stormtrooper (also expensive, and time-consuming).
Speaking of the Empire:
Creating an army of clones is easier and cheaper than hiring (or enslaving) people, indoctrinating them for your purposes, and ordering stormtrooper uniforms of different sizes.
None of the clones become fatter or thinner than the others, or grow up to be different heights because of different conditions before and after birth.
Medicine sufficiently advanced to create an artificial hand that is the same as a natural one from the user’s point of view, or to save someone with third-degree burns over a large part of his body exists, but there is no prenatal care capable of determining that a woman is carrying twins.
[ul]
[li]Virutally all alien worlds and large moons have a surface environment that is remarkably like Southern Califonia. (Those that don’t either resemble Redwoods National Forest or Tunisia, except for the rare “icy moon”, which looks like someplace in the Arctic Circle.) [/li][li]There is a grossly disporportionate number of worlds with an oxygen/nitrogen atmosphere that is sufficiently close to 1 bar–even otherwise lifeless worlds–to permit crewmembers to wander about in the aforementioned spandex uniforms. [/li][li]Evolutionary diversity is greatly restricted on other worlds, often to the point of having just two species.[/li][li]Bipedalism is a dominant feature in parallel evolution of virtually all sapient lifeforms.[/li][li]Alien cultures are monoethnic and monolinguistic.[/li][li]One can reduce the entire instinctual behavior and common philosophy of a species to what they had for dinner.[/li][li]Everybody in the universe speaks English, unless the plot otherwise requires a species to speak another tongue. [/li][li]In the future, emergency power supply priority is such that artificial gravity takes precidence over environmental control.[/li][li]Don’t push the big red button until you are a fraction of a second away from total annihilation, upon which it will suddenly transport you out of trouble, rendering only minor injuries in the process.[/li][li]Time travel is impossible, unless you need it for the plot, in which case you just reverse the polarity and slingshot around a convenient gravitational anomoly or something. (I forget exactly how it works but I’m sure the science officer can figure it out.)[/li][li]Magic replication technology will allow you to manufacture the most intricate of items except for those vitally needed to resolve a plot conflict.[/li][li]Even if you have a technology that allows a living body to be disassembled to component atoms, beamed through space as an electromagnetic signal, and reassembled in mere seconds, you’ll still have people who suffer from infection and degenerative diseases. Go figure.[/li][li]Always mount an accessible off-switch to the sentient, autonomous computer that controls your spaceship or strategic weapon system.[/li][li]Beware of people who are obsessed with bodily fluids. Do not put them in charge of a major strategic weapon system.[/li][li]It bodes ill to be the most junior officer on an away team or boarding party. Report to sick bay immediately.[/li][/ul]
Stranger
In the future, no one wears hats. Except for those guys who blew up the Krell.
Which reminds me… no matter how advanced or evolved a culture or civilization may become, there is always some way that we Humans can reassure oursleves that we are morally superior.
Once out in deep space, everyone will forget that there are at least 3 spatial dimensions, thus forcing most battle or retreat strategies to be limited to right/left/forward/back.
Let’s see… I’ve learned that the surface orbital period about a spherical body depends only on the mass of that body.
Reaction mass is most efficiently ejected near the bottom of a gravitational well.
Human behaviour is easier to understand in the statistical aggregate.
A toroidal structure around a large central mass is in equilibrium, but is not dynamically stable.
Even a very low constant acceleration adds up, if you can maintain it long enough.
Heinlein-lover!
Stranger
Argh! Density! It depends on the density of the body, not the mass!
I would have said “Niven-lover” myself.
My point was that when and if the human race develops FTL spaceships that are cheap and efficient enough to make interstellar colonization possible, they just MIGHT have developed a few other technologies to make life more comfortable as well. I imagine a dirt-poor colonist of the future will live a life that a current millionaire would envy, in some respects. I’m not buying this rags-and-mud-huts stuff at all. It’s all people with little or not imagination looking at the future, unable to imagine what a really wealthy interstellar society might be like, so fallilng back on primitive shit.
For a positive example of someone thinking intelligently about the future, try Iain Banks’ Culture novels.