This question originally appeared on Quora. 
By John David Ward, teacher
I don't know whether what's mind-blowing to me is what's mind-blowing to you, but here are some of the possibilities.
- Roughly six million years ago, the ancestors of humans and the ancestors of chimpanzees regularly interbred (they were the same species, of course). Just think about it.
- Contrary to those posters you see, the ancestors of humans were fully erect long before they developed brains larger than those of chimpanzees.
- Empathy is computationally expensive, and the physical limits of our brains create an upper bound on how many other people we can interact with, keep track of, and generally "grok." This is called the monkeysphere and has been estimated at around one hundred and fifty, but it could potentially be two or three times as large, depending on how it's defined. Beyond this point, our ability to treat others as humans, rather than as objects, begins to decline.
- Human beings, and the human world, are very, very large and very, very slow. Our tendency to use anthropomorphic units of measurement obscures this. The natural unit of length, the Planck length, is about 1.6 x 10^-35 meters, or about 3 x 10^35 times smaller than the average person. The natural unit of time, the Planck time, is about 5.4 x 10^-44 seconds long. Describing it this way makes it seem like it's a matter of physics, but it's not. The Planck time and the Planck length are what they have to be. These numbers actually describe us and the entire world we apprehend. These numbers are physical constants only in the sense that we ourselves are physical beings.
- We're used to describing humans as mostly weak and unremarkable except for our brains, but humans are actually quite physically adept at many things. For instance, for tailless bipeds, we're extraordinarily good runners. For primates, we're excellent swimmers. By the standards of mammals, our sense of smell is poor, but as mammals, it's still pretty good. Our brains are the coolest, but there's a lot that's interesting about humans physically, too.
- Humans survived for hundreds of thousands of years without any government or written records, and only minimal economic specialization. As a result, we're living in societies that are really too complicated for us to understand, and which, as a result, are counterintuitive in many ways.
- Subsaharan Africa contains most of the genetic diversity in the human race. Outside of Africa, we are all pretty much inbred. This is one of the big problems with the traditional division of the human species into races.
- Although human races don't exist at the moment, farther back in our evolutionary history they did. Extinct human races include at least the Neanderthals and what're nick-named Hobbits. There may have been more that we don't know about now. All modern humans happen to be descended relatively recently from the single surviving human race.
- Neanderthals were redheads.
- Illegitimacy is usually underestimated. Worldwide, about 10% of people are not descended from the man they think is their father. In places with weaker taboos, this may be closer to one third.
- Anthropology is rife with fraud and accusations of fraud. These are doubts about the accuracy of some of the most famous anthropological case studies, such as Margaret Mead's Coming of Age in Samoa (see the Mead-Freeman controversy). Consequently, all ethnographies (reports on cultures) have to be taken with a grain of salt, something that non-anthropologists don't really seem to take into account.
- Although they've made bits and pieces of progress, anthropologists still have never been able to develop a purely behavioristic (ethological) explanation of human society. Behaviorism and the idea of conditioning, which works relatively well in individual cases, don't scale up very well.
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