Is civilization possible without slavery?
I don't know that it is. You can read online that not every civilization has had slaves, but then again, most have. Certainly the most "civilized" have kept humans as chattel. In the West, our origins are tainted by this fact, as Athens and all of Greece was a slave society, and Rome, the West's Classical model, was very much dependent on the slave class. I'm not even getting into the Arab slave trade, nor what was going on in the East, which were monumental in their own ways.
There was less slavery at other times. It declined in the Dark Ages and on into Medieval Europe. Not to the point of being absent, and it differed country to country, but it was largely replaced by serfdom. Which is still basically forced labor, though not as explicit and carrying somewhat more freedom. But then the Renaissance hits, the great "rebirth" of Western civilization, and what does it bring? The horrors of the African slave trade, the enslavement of whole nations of Native Americans, plus indentured servitude, which was in some ways worse, as far as how the people were treated (an African slave was an investment for life, so was somewhat less abused than someone only "owned" for 4-7 years. They worked the latter to death, more often than you'd think, to get their money's worth).
I've heard that if people had been civil and patient, slavery in the Old South would have died out on its own, without the national bloodletting of the Civil War. Much the way Canada waited patiently to themselves eventually split from England by a gentlemen's agreement, no Canadian Revolution required. Canadians like to use these examples to prove how violent we Americans are. They are only partially right, because things aren't black and white or simple like that. There were principles at stake, and institutional human suffering, and these are worth fighting for and against, respectively.
Thoreau had something to say about this:
When the majority shall at length vote for the abolition of slavery, it will be because they are indifferent to slavery, or because there is but little slavery left to be abolished by their vote. (1)
It's true, it would have ended of itself, the way things were going. But only because we replaced human slaves with machine slaves. Be certain that I am not saying that it is immoral to use machines to do our work. I am simply saying that slavery has not been abolished, only mutated and changed. Of course, there is still wage slavery, as machines have not replaced all human labor, and actual human slavery still persists in pockets all around the world, even here in the US. But that is not my overall point here. The point here is that high civilization is not possible without free labor, and that the degree of civilization is based on how much free labor (energy) is available.
Hell, take animal domestication, the final nail in the slavery case. No civilization has existed that did not have domesticated animals, that is, enslaved animals. Perhaps the American civilizations like Cahokia, the Aztecs and Maya did (the Inca had llamas), but they practiced human slavery, were not as stable or long lasting, and not as developed (at least in the case of Cahokia) as, say, Greece, Rome, China, India, or the Arab world. That is, they were not as far removed from the hunter-gatherer and simple horticultural models they grew out of, and that is why they so easily disappeared back into those models when their civilizations dissolved (in the case of Cahokia and the Mayans).
Animal slavery is where higher civilization began. It's one thing to keep a herd of sheep around to eat, or even cattle for milk and cheese and meat. But when you strap a saddle on a horse, or a yoke on a pair of ox and force them to do the work for you, you free up human labor to do things like form more refined administrative techniques, writing, art, religious embellishment, war, and technological invention.
And it all comes down to energy, no? The Age of Fossil Fuel is exactly the same as the Age of Animal Domestication, in that the vast power available in either the livestock or the oil barrel frees humans from drudgery and labor to do other things. Each is a step up of an order of magnitude from what went before. That's why higher civilization developed out of the use of animal labor, and why the Industrial Age sprung up when we tapped the energy of machine labor running on fossil fuels.
This is the issue around which our current energy woes revolve. Naturally no labor is free, even slave labor, since the slaves need to be bought, and fed, and at least minimally maintained in good health, much as a horse or ox needs to be. Likewise the machine, which, while often cheaper than human workers, still needs maintenance and fuel. It's funny, the way the owner class comes to depend on its slaves, and the energy they represent.
So now the upshot. If it turns out to be true that Peak Oil is not resolved via new energy sources, things are going to decline in complexity. This is obvious, but one must understand what's at stake. You read books like James Kunstler's A World Made By Hand, and it seems like democracy and freedom largely survive the fall. I wonder at that. Power doesn't let go so easily, and I wonder if instead of a sort of benign localism of freeholders and townsfolk, we won't end up with something more akin to a world under a myriad of Pol Pots. Those used to living high on the hog are not going to want to climb down, and I fear that they will simply see that as the oil energy goes, they must return to human energy in the form of serfs and slaves.
(Finally, check out this link, and savor the irony)
(Finally, check out this link, and savor the irony)