Second, this post will contain spoilers for the manga and anime, so if you are not up to date with chapter 79 beware of being spoiled.
At first sight this manga is set in a 1700-1800 era society with some steampunk additions. From the start we are led to believe that while the society is indeed post-apocaliptic, they haven't lost much technology from the past, and in fact have advanced in some areas.
The apocalypse is brought by the most unlikely threat, though, a race of human-looking giants, apparently dumb, but that possess incredible strength, regeneration and who don't even need to eat, but would go to extremes to eat humans, while ignoring any other plant or animal.
This manga is exceptional in that while it has definitely an element of action and adventure to it, and most mangas would stop at that and call it a day, instead it's main focus is on mistery: both the readers and main characters don't really know anything at all about the world, and little by little we are both given clues, some faint, some clear, some only make sense much later, but they are there from the start.
-Genetically engineered supersoldiers (Ackerman clan).
-Serums far more advanced than whatever the people within the walls can analyze, let alone create (titan creating serum).
-Titan-shifters that: 1) wear modern clothes 2) drink coffee 3) know baseball 4) can infect or mass produce the titan creating serum that the humans from the walls can't even study.
All this, together with how we know the Reiss used the coordinate to wipe out the previous history of the world for those living within the walls, points towards a society far more advanced than our current real-world existed, one that is at least somewhat mantained by the shifter village.
Now that we know the giants are not some mythological creatures, and the Ackermans not some random badasses, but rather biological weapons and tools engineered by an advanced society, how do you think those could possibly work based on modern science, and why were they created? Or is it all amateur scifi gibberish?
Ackermans: superior strength, speed, reflexes, stamina, focus and possibly intelligence. Think Captain America levels of fitness; in one chapter we have a 1.60 Ackerman dragging a 1.80 corpse up a roof with one hand while he climbed with the other, fast. Hereditary power.
(Dumb) Titans: go from 2-3 meters up to 50 meters (colossal titans within the walls). Humanoid. We now know they are all humans that were turned into that form. No clear female characteristics even if created from a female, no reproductive organs. They regenerate all kinds of wounds almost instantly, including the brain, all except the nape of the neck, which is also where a titan-shifter would be placed, cutting off a large portion of that area kills them. They have very light bodies, an arm several meters long can be easily lifted by a person. They don't need to eat anything, but will chase after humans and titan-shifters, can be entombed without light, food or air for extended periods of time and remain alive. They seem to generate heat, in particular the skinless titan-shifters.
Titan-shifters. In human form they have: extreme regeneration, survival to almost all kinds of wounds, can transfer their conciousness out of their brain to other parts of their nervous system or to their titan, can survive being frozen without food and air for extended periods of time (Annie is alive but trapped in a crystal in human form, the titans in the walls are trapped without light or air but alive, Reiner gets his whole head blown off and survives, Ymir regenerates having her body crushed, almost all shifters had body parts cut off and fully regenerating quickly). And of course, all titan shifters can, upon inflicting a small wound on themselves, invoke a titan that goes from 7 meters up to 60. The creation of this titan is almost instantaneous, cause some kind of lightning centered on the shifter, apparently needs to be done under sunlight (might be possible to do it if there is moonlight), and the only apparent cost to the shifter is becoming tired after using it, and possibly reducing their life expectancy. Some titan-shifters can control dumb titans when they are in their titan form. The only way to create a new titan-shifter, that we know of, is for a dumb titan to eat the nape of the neck of a titan-shifter.
The Coordinate: we are led to believe it is a titan-shifter with exceptional powers, such as controlling dumb titans, humans and possibly titan-shifters at will, including erasing or altering their memories. They can pass the memories of the previous owner from generation to generation to the point the original personality of the first Coordinate owner remains almost unaltered, even if repressed, through their whole family line.
This seems at odds with the fact that unlike titan-shifters, the Coordinate can actually control titans and humans while he/she is in human form, and force them to perform very complex operations.
So what do you think? what were each of these engineered for, and what are they made of, specially the titans and titan-shifters?