I'm trying to get my bearings straight with some of the highlights of human and pre-human history. Can anyone confirm or deny the following account (and feel free to elaborate where it seems helpful--particularly in regards to technology, which is my main interest)?
Australopithicus evolved from earlier primates in central Africa about 2 million years ago (rough timeline), and at a certain point spread out from jungles to savannahs. The latest species of this genus used very primitive stone tools. From Australopithcus the first hominid species evolved, and from that hominid, several other hominids evolved. Some of these hominids were increasingly human-like and started fashioning more sophisticated stone tools like the hand axes.
Australopithicus had at some time spread out from the jungles to the savannahs of north/central Africa and eventually through Asia. Hominids also began in Africa and spread throughout the world. When humans finally did likewise, about 50,000 years ago, wherever humans arrived there coincided an extinction of the other hominid species in that region. Humans also spread farther than previous hominds, to more northern climates and eventually the Americas.
At this point people are hunting, gathering, and in particular a lot of the plants that they like the best are having the best odds of reproductive success. The environment was adapting to the presence of humans, and slowly turning into a form that would allow for domestication much later. Wolves may be staying closer to human camps for whatever reason, possibly to get our food scraps. Any aggressive dogs get killed, which was also applying selective pressure on their population to transform them into a domesticatable form, namely the dog. Climate change might also have driven humans and animals toward scarce water resources where they would have to live together. Possibly with early forms of cattle, sheep, or pigs, humans would have to make sure that the animals don't die out. That means killing the right ones at the right time for food but also protecting the herd from other predators, etc., which could have laid the foundations for early sherpherding.
About 10,000 BCE we see some societies slowly adopt practices that would morph into agriculture. In the Fertile Crescent the Natufians gather wheat and other crops that can last over a year after harvesting if they're kept dry. But the need to carry the wheat causes them to build storage structures and tend toward sedentism, although much of their diet still derived from hunting. Due to the Younger Dryas they had to abandon these structures and return to foraging, but with the retreat of the Younger Dryas they might have re-settled areas where domesticable plants and animals were available.
The Catalhoyuk civilization may have represented a joining of people practicing sedentary crop gathering and shepherding. This constituted a very nearly agricultural society, although it's not clear that crops fully depended on humans for reproduction and therefore may not have been fully agricultural.
Other people developed agriculture independently in other regions, including the Indus Valley, two eastern Chinese peoples along the Yellow and Yangzi rivers, the Central American Olmecs, and the South American Norte Chicos. Less is known about these origins because we haven't yet conducted the necessary archaelogical research.
Societies tended to wax and wane in their development of agriculture, sometimes abandoning it completely, probably because it was more work than it's worth. However, when a society developed agriculture, it would afford it more power in the ability to give larger gifts at inter-tribal meetings and in the ability to raise larger armies in wars. Agricultural societies would then often forcefully dominate neighboring societies or neighboring societies would adopt agriculture in response, as an attempt at defending themselves.
Internally, these societies would develop increasingly complex political structures. In general a leader would justify his (usually a male) power by religious claims, or by claiming that he could defend the civilization and wage wars for the profit of the civilization. Still, priest and military classes would often grow separately but in some parallel. Increasingly, people would perform specialized work. Their living quarters were initially compact and communal but continually become more spaced and distinct.
Socieities relevant here are the Minoans, Egyptians, Akkadians, Sumerians, and Chinese. Later the Babylonians, Assyrians, Phoenicians, Aryans, and Hittites would be the relevant, large societies, and then Mycenaeans, Greeks, and a host of others, I'm sure. A complex struggle between various of these would ensue, which I'm not yet able to even attempt to describe or even understand.
After agriculture the most significant technological advances to come would be writing and bronze work. Writing probably came as an evolution from the artistic representations that had begun in even the earliest human and other hominid tribes, tending toward greater abstract symbolic representations. It was also necessary to have an agricultural society in which an educated class could develop and share a writing system.
Bronze working required the amalgamation of copper and tin. The discovery of copper probably came around by accident. We know some pre-agricultural people used malachite (copper ore) as ornament because it's a pretty blue rock, and ground it up as body paint. Since copper melts at the temperature of a camp fire, it is plausible that some could have fallen into a fire and they'd have observed the resulting pure metal the next day when they dug through the fire site. They had pottery enough to perhaps be able to shape the metal into rudimentary tools, but since copper alone is soft, they probably couldn't have made extremely useful tools with it. But as they then perhaps tried burning more rocks at higher temperature to see if they could get metal out of them, they may have discovered tin, and then discovered that the resulting mixture makes for a very strong metal that could make tools strong enough to take down trees and even be used for building material in some rare cases.
Iron followed after this, and while iron is stronger and makes better tools and weapons, this usually isn't a huge advantage for the overall success of a society. Rather, the significance of iron is the advanced technology necessary to smelt it, and societies that produced iron were remarkable because of their underlying social organization and greater knowledge in general.
So is this roughly accurate, did I get anything wrong or miss really important points?
I'll give it a try. This is a huge topic, so I'll gloss over some of the details that are maybe not entirely correct but more or less get the idea in favor of adding missing details or correcting false ones. Seems like you've done some good research already though!
You are correct that a lot of hominid evolution (such as bipedalism) was spurred on by living in savannas instead of forested environments. However, it was less that our ancestors moved out of forests and more that climate change resulted in a contraction of forests in Africa. Environments that were previously forest dried out and became savanna with patchy forests, forcing our ancestors to spend more time on the ground and ultimately develop bipedalism.
Let me make a correction to your explanation of human migration out of Africa. Australopithecines never left Africa. The first human species to leave Africa was Homo ergaster (previously known as Homo erectus) which made it to Europe and most of Asia. Otherwise, you've got the right idea about the spread of Homo sapiens.
Your discussion of the origins of agriculture is more or less correct, but you are missing probably the most important component that led to domestication, which is the Broad Spectrum Revolution.
With the Pleistocene coming to an end and the general warming of the planet, a lot of the megafauna which early humans exploited heavily (e.g. mammoths, aurochs, giant reindeer and bison, etc...) began to die out and be replaced with either smaller varieties or other species. Partly because of this, humans generally began to diversify the kinds of resources they exploited. In short, they had to use a lot more kinds of resources to meet their subsistence needs than they did before. This has two important consequences in that populations were generally more sedentary than before and people had a new kind of relationship with plants and animals. When before you had people following herds of animals across the landscape, you now had people generally staying in a more limited region (but still moving through that area) and exploiting geographically restricted resources on a seasonal basis. For instance, moving up to the mountainsides to exploit the stands of oak for acorns in the fall and them moving to the coast to hunt seal during the winter. Additionally, this Broad Spectrum Revolution brings people into a much closer relationship with certain plant and animal species, laying the ground work for manipulating them on a yearly basis. For instance, harvesting squash along a river in a particular season and selecting seeds from the largest squash to plant and collect in the following year. All of this eventually leads to your Natufians relying on stands of wild wheat for subsistence, but you see the same pattern basically everywhere else on the planet.
For the origins of agriculture, I'll just make a few corrections. While the Olmec are one of the first complex, sedentary, and agricultural societies in Mesoamerica, they didn't invent agriculture there. There are some smaller-scale agricultural societies prior to the Olmec. In fact, the major agricultural staple corn was likely domesticated in central Mexico much earlier than the first Olmecs down on the Gulf. That said, some very early corn has been found in the state of Tabasco in the Olmec homeland.
For South America, as far as we know, the Norte Chico cultures didn't actually begin as agriculturalists, but rather transitioned to agriculture after they started building monumental architecture and exhibiting other characteristics of complex societies. They began by domesticating and growing cotton rather than food crops, likely to weave nets to better exploit the rich fisheries off the Pacific coast of South America.
Finally, it is important to note that crops were domesticated and sedentary agriculture was invented independently in both Western Africa and in the eastern woodlands and Mississippi valley of North America.
The origin of states and complex societies is not a subject I'm going to touch in much detail, because it is a huge and quite contested topic. Suffice to say, there isn't really any one explanation for why people started living in states. What seems to be the case is that a lot of different factors contribute to people becoming sedentary farmers and living in states, and those factors aren't necessarily the same in all of the places were early states emerged. I've added two sources with differing perspectives on state formation, but know that that is a vast and diverse field of research.
In general though, the push towards sedentism and agriculture seems to be motivated not by technology or domestication of plants, but by population pressure. As populations worldwide began to grow, the land available for people to use to support themselves began to shrink. This can lead to a lot of different catalysts for state formation. For instance, warfare to take control of resources. Alternatively, you have a situation where adopting agriculture is an effective strategy for producing more with a smaller amount of land. It is actually probably harder to support yourself as a farmer than as a hunter-gatherer. However, if you don't have the option of being a hunter-gatherer because of population pressures, being a farmer beats starving!
As for relevant societies, don't forget what is going on in the New World and South Asia (India-Pakistan). You have early states in South America such as Chavin, and in Mesoamerica such as the Olmec.
Just a note, but you might be overestimating the importance of metalworking and writing. You have tremendously complex states in the New World that function without any writing, or very minimal writing, and by mostly using stone instead of metals. As you mention, complex social organization isn't tied to having metals, although many of the societies that pioneered metallurgy did have complex social organization.
I suppose the last thing I would add is that it this is a very particular story of the development of state society, but even after the development of states and complex societies, large portions of the population on the planet didn't live in particularly complex societies. Just as some perspective, even though we make a big deal about the first cities and how significant they are, the majority of the population of the planet didn't live in what we can call cities until as recently as 2008. There are still hunter-gathering groups making a fine living today, and many times more if we go back 200-300 years. Not that you imply this in your post, but it is important to talk about how non-state societies change and developed over the course of the last ~5000 years just as much as state societies because that is just as much a significant part of human history as the story of states and cities and such.
Sources:
[Craft specialization and old world states] (http://link.springer.com/article/10.1023/A:1022801712684#page-1)
I can't really answer your question, though from my amateur perspective it seems like your view is correct in very broad strokes. I did want to say that you may want to ask people in /r/AskAnthropology as well, particularly about the early, pre-history aspect of your narrative.