What the heck happened between 1 million years ago and now? The human race changed a lot and matured very much, but it's so incredible that such a big evolution only happened in the last few thousand years and the rest has taken hundreds of thousands of years.
The documentary Cave of Forgotten Dreams[2] presents the cave in a breathtaking detail, definitely worth a watch.
They must have been members of what David Deutsch calls a "static society". These are societies which actively try to keep things the same, and stamp out any innovation or differences. Things change there so slowly that the change is not noticeable within a single generation. In a 2011 interview with Ken Rose (https://groups.google.com/d/msg/beginning-of-infinity/dr64n4...), Deutsch said that "progress, from the point of view of the human species as a whole, is very recent and very rare. Through most of human history, people would live their entire lives without ever encountering an innovation, whereas now, we take it for granted that iPhone updates come more often than is comfortable."
For more, see his superb book The Beginning of Infinity (2010).
Agriculture appears to have been developed independently in the Middle East, China and Americas about 10,000 years ago, but I and some others believe there was more dissemination of ideas, mainly via individual travellers or small groups of travellers, than conventional historians take into account.
A boring answer to this question is that it was simple incremental changes driven by random mutations and natural selection (eg. evolution). For example, we might have started to occasional plant the seeds of plants as we found them, which could become us regularly doing so. Then we might have started moving the seeds to more central locations, and eventually arrive at agriculture as we know it today. These adaptations may have started before homo-sapiens. If it happened long enough before (so that there is another species with a common ancestor that did this), we could check this by looking for agricultural tendencies in species related to us (If anyone is aware of research on this hypothesis, please post).
A more interesting hypothesis is that agriculture was the result of an abiotic change. Instead of gradually developing agricultural tendencies, we 'immediately' became agricultural following some other event, such as a change in climate. This seems to be consistent with my understanding of climate history, which puts us in a relatively short window of nice climate.
We think agriculture and city-building started around that time, but it's possible we just haven't found older evidence because it was destroyed when the ice age ended and sea levels rose.
It seems incredibly arrogant to me to think that our ancestors, who were virtually identical to us much of those million+ years, required at-minimum hundreds of thousands of years to figure out what seeds are and how to make them grow. These are people who knew how to live off the land and were far more familiar with plants and animals than most of us could dream of being. These people invented astronomy, art, religion, clothes, tools, fire. They'd notice that plants produced seeds, that seeds wound up on the ground, and that new plants grew where the seeds fell.
Anyway, if you look at tribes native to the America, about all of them knew about agriculture (it's in their culture), but not all established an agricultural society. What we are calling "developing agriculture" probably is a much more complex phenomenon, with several different (near) contemporary developments, and probably none of them was learning that plants grow from seeds.
* Ok recent humans certainly were similar, and agriculture could probably have appeared a few thousand years earlier, I'm not sure we can extend that to hundreds of thousands, or maybe even tens of thousands.
Il flip your arrogance accusation around. These people developed agriculture and even cities tens of thousands of years ago, yet none of them managed to put together a sustainable survivable civilization? None of them managed to go from basic agriculture to even slightly more advanced agriculture that would have launched them on the track to specialization, even given hundreds of thousands of years in which to try? Why not? What was wrong with them?
To a hunter-gatherer, which is a nomadic lifestyle, cultivation in a fixed area for long enough to both sow and later reap a crop is not at all obvious.
"Fungus-growing ants practice agriculture and have been doing so for the past 50 million years according to research published in the Jan. 17 issue of Science. These ants not only grow fungus gardens underground for food but also have adapted to handling parasitic "weeds" that infect their crops."
Which leads to an off-topic question: Is mushroom cultivation considered as agriculture?
There have also been agricultural civilizations that grew rain-fed crops on forest sites and built houses of wood. Like the Maya, or ancient southeast Asian civilizations.
Luckily those peoples did help us out by building stone temples, but I would assume that probably several more civilizations have practiced slash-and-burn jungle agriculture and just not happened to have built monumental temples.
Supporting my hypothesis, one early layer of Jericho seems to reflect a forestal mode of production - something about acorn horticulture[0].
So, I think if we are to find the hidden backstory behind the sudden simultaneous 10,000 YE agricultural revolutions, the place to look would be in the trees. But what do I know.
[0] http://en.wikipedia.org/wiki/Natufian_culture#Settlements "Settlements occur in the woodland belt where oak and Pistacia species dominated...The superstructure was probably made of brushwood. No traces of mudbrick have been found."
an exponential process (of life complexity in this case) looks the same at any scale. The Earth has existed for 4B years, life is ~3B years, life as a cell with nucleus ~2B (yea, 1B years to develop nucleus :)
i kind of see it here. The evolution speed depends on the speed of generating of changes and on the speed of selection of the generated changes.
Wrt. the speed of generating of changes. The more complex a system (i.e. types and number of actors/components and relationships between them) - the more diverse set of small gradual changes/variations to components/relationships/behaviors can happen while the system will still be functioning. In particular it is applicable to biological systems, ie. single cells, colonies, multicell organisms and various groups/societies of it. For example, in general, 2 different species of cells can produce more diverse set of natural variations than 1 species even if the total number of cells is the same in both cases. An example at different scale - one science - philosophy of Ancient Greeks has become a multitude of sciences through the same process of branching/specialization and the speed of this process is proportional to the number of branching/specializing sciences. Following the same principle - there is no way US tax code (or the law in general :) will become simpler anytime in the future :)
Technological advancement tends to follow that pattern, and I imagine many evolutionary changes do, too.
* stone hand-axe: http://en.wikipedia.org/wiki/Acheulean
* fire: http://en.wikipedia.org/wiki/Control_of_fire_by_early_humans
Sadly, I must once more indicate that this post is sarcastic, for the humor-challenged ones.