At age 7, due to my fanatical obsession with airplanes, I had a fairly complex understanding of flight, such as the various flaps on a wing, what feathering a turboprop engine meant, Mach speed, the stratosphere, etc.
I may have lagged behind my peers in most other social or academic aspects, sadly, but at least when it came to planes I was a walking Wikipedia.
What was your childhood area of info expertise?
The Watergate scandal. I was 8-9 when it was going on, and I was fascinated. My parents would have their friends ask me to explain it, and I would tell them all about the various illegal activities and the people involved. I remember seeing a story on T.V. in which they asked little kids to explain Watergate, and I couldn’t believe the wildly wrong answers they gave.
One of the top items I was hoping for when I grew up was to learn the identity of Deep Throat. It took 31 years, but I was finally able to cross that one off my list. (I knew that the pseudonym came from a porn movie, but it was a long time before I learned what it meant.)
I was an odd solitary kid with a philosophical bent. I have a clear memory of being in a car with my parents around age 8 or 9. They were driving through the main street of a town; people were parking along the side of the street and coming and going from stores along the street. Other people were working, unloading things from trucks or sweeping the sidewalk. It was a bustle of normal daily activity. And I had this sudden thought-- what is the purpose of it all? We eat, we sleep, we play, we work at jobs, but what’s the greater meaning of it, if anything? Why are we here? Why do we do anything at all? Thus I had my first existential mini-crisis and began my personal struggle with the ultimate meaning of life.
I had another clear revelation one day while walking down the hall of my Junior High School to class: without the existence and knowledge of evil there could be no goodness, or at least we wouldn’t be able to recognize goodness as goodness without the existence of evil to contrast it with. Therefore evil, as undesirable as it is, is nevertheless necessary (a necessary evil, ha). It was years before I learned of Taoism, read the Tao Te Ching and found out I wasn’t the first to think of that; in fact I was beaten by 2,400 years.
When I was very small I couldn’t understand what made us, and other living things, stay alive. If, as it was carefully explained, we are mechanical systems, extremely complicated machines, what kept us going? Why didn’t we just stop, when something broke inside, like a car? Why did we instead heal and go on?
Then I realized that what was different was that we wanted to live. The desire to live was, itself, what made us alive. And everything living was imbued with this same desire.
I had no one to talk about this with, but it was a strong revelation which is with me yet. At the time it was very reassuring, as it was frightening to think that we were nothing more than machines which once broken just sat there dead or dying unless someone fixed us.
This happened before I ever went to school, so maybe I was four or five.
When I was in Boy Scouts, we would often, on a camping trip, make foil-pouch meals: You take a hamburger patty, and a potato, and some veggies, and maybe a raisin-stuffed apple for dessert, and wrap them all up in foil and toss the foil into the coals of a campfire to cook. There was much debate about whether the shiny side of the foil should be facing in or out, but I insisted that it couldn’t possibly matter, that a substance couldn’t possibly reflect heat better in one direction than the other. Which prompted some of the guys to do the experiment, and conclude that I was right.
I had those last night for dinner. Put 'em in the oven… delicious!
Anyhoo, I can’t think of a specific area of knowledge , but I started reading words when I was about 2 1/2. Does that count?
I was 6 years old when I reasoned out that Santa Claus couldn’t be real. The world was just too big, the time interval too short, for him to do what they said he did.
When I learned about the Socratic Method, I realized I had already invented it and been using it as long as I could remember. Yup, me and Socrates, birds of a feather.
I was 7 years old:
"Hey, Dad; could you use the spinning of a car’s wheels to generate electricity to keep the battery charged? "
“Lemme tell you what an ‘alternator’ is, son.”
Well, in contrast to what I often heard said about young children’s moral development as an adult in a classroom, a strong sense of moral code.
Our elementary school’s classroom doors opened to the playground, not to a central hallway. (Think of a low-end motel and how the doors open onto the parking lot). I was in a line of first graders and standing next to us were the kindergarten kids, all of us waiting for the bell to ring and the doors to open to let us in. The first graders were taunting the kindergartners, singing the taunting song at them about them being babies. And I was all outraged and offended, because we were all in kindergarten just last year.
I don’t remember the details of the event so much as what followed, but not long after, there was a kid I didn’t like, and I saw him reach into his own book bag to get something. A moment later a girl on the next row said something had been stolen from her and someone sitting nearby said they’d seen the boy I didn’t like reach over just now and take it. Someone else confirmed that. Teacher asked for a show of hands and a lot of people testified that they had seen it happen. I said I’d seen him reach into his own book bag and that was probably what everyone had seen, and he hadn’t reached to the girl’s desk or into her bag.
I was all full of abstract concepts about fairness and honesty and doing the right thing and caring about what other people experienced even if you didn’t like them personally, and trying to work out rules for everyday life situations that would honor those principles.
Apparently, according to theories of childhood development, I wasn’t supposed to be capable of having such thoughts, I was only supposed to be able to fear personal consequences of getting caught or having other kids be mad at me or whatever. Dunno if that’s universal bullshit and all the other kids were contemplating such matters, or if I was doing something advanced for my age.
That’s very admirable. I guarantee you that that kid never forgot what you did for him that day.
I did too at the same age, but it was after a quick perusal of a globe one Christmas, when I realized that there was no solid land at the North Pole, and Santa’s castle would quickly sink through the ice. I ran downstairs and announced my sudden revelation to my shocked parents. [I still got my presents however]
I have spent the majority of my life wondering about this. Just yesterday I was wrapping something up to reheat in the oven and I had to stop and think “is it shiny side out?”. Glad to know it doesn’t matter!
Not sure if this counts as “understanding” but I empathy seems to have come naturally and early to me.
I also remember being very young when it occurred to me how damned lucky I was to be living in (to me) the greatest place in the world. Not in a braggy “California rules!” way, but in loving everything about the place and realizing I did nothing to earn that privilege. All credit to my parents who moved there in the late 50s from Chicago. I also love Chicago, but I’m glad they made the migration.
I was in 4th or 5th grade catechism class when I realized how ridiculous the Catholic religion was. Not sure whether that is advanced or simplistically obvious. 
Driving starting when I was 11 through 14. Trucks, cars, tractors, motorcycles.
My grandfather built and owned a 230 lot mobile home park. And I worked there on weekends. My truck to use was an old Chevy with three on the tree for getting around the mobile home park. Did everything from installing gas lines to lots, to repairing streets. And the every present mowing of grass.
I still remember how to use a RIDGID pipe threading machine for threading/cutting pipe for gas lines. The driving part was the most helpful though. But the time I got my license, it was no big deal at all.
The same for me. Read everything about them I could get my hands on. Another plus was my uncle was an aircraft mechanic at an airline and he was a wealth of info to me, and another uncle had a small plane he used to give us kids rides in.
WW2 history is another: Aircraft, guns, ships, tanks, battles, tactics, personalities. I greedily accessed any and all reading material of it I could. By the time I was 12, I could out Wiki Wiki, even if it didn’t exist then.
When I was about 12 I realized that parking fines (letting your meter run out, for instance) were not designed to punish you for parking misbehavior; they’re designed to generate revenue. And a little later: that a lot of laws are designed to be broken, so that every citizen is constantly in violation of some law or other, and can thus be controlled.
(p.s., I am not a libertarian.)
This probably doesn’t count but I’ll post it anyway.
When I was a kid, I had seven imaginary friends. I could only “see” one of them though. And I would have to communicate to the other six through the one I could see (His name was Rice, the other six didn’t have a name). Usually the group acted as a counsel with “Should I or shouldn’t I” types of situations. We would also ponder existential stuff as I lay in bed at night.
Anyway, not advanced, but that’s a rather complex imaginary friend to have at such a young age.
Maybe I’m not understanding you correctly but “the desire to live” has nothing to do with healing injuries. 
I was always very good with maps, and was official navigator on family holidays from the age of eleven or twelve, I would guess - as in full responsibility for route planning, keeping us on track etc.
I have always attributed this to being raised in West Cumberland (as it was then) - with the Irish sea on one side and the Lake District mountains on the other. For almost all purposes you either went up the coast or down the coast, and that was it. Put me in two dimensional space and I was (literally) lost - hence the need to understand maps.
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