The transition from hunting and gathering to full-blown agricultural civilization took thousands of years, and constitutes the single most impressive jump in human development. But that doesn't mean that humans thought any more sequentially once they started living in cities. One would think that, with the specialization that civilizations could afford, hot-shot thinkers would arise who would have discovered sequential thinking -- but it didn't happen until after writing got started and really seeped into the consciousness of the people.
Mesopotamiam law provides us with good insight into the development of sequential thinking. At first it was nothing more than a collection of if-them statements, exactly the same kind of thing that hunter-gatherers developed for their environment. With time, a small amount of subjunctivity developed; but at no point did abstraction appear. However, the Mesopotamians did make one big leap forward: they invented writing. Although they themselves did not use this technology to advance human thinking, they at least set the ball rolling.
The Eyptians represent an interesting transitional case. They had something like algebra, definitely involving sequential reasoning, but it seems that this style of thought did not penetrate deeply into the Egyptian mind. They used no sequential reasoning in their criminal justice system, nor did develop much in the way of abstract thinking.
The next big step in the process was the invention of the alphabet. Some Semitic genius came up with the idea of representing individual sounds rather than entire words. What a concept! The Phoenicians came next, and they had two important advantages that the Egyptians lacked: an alphabet and and extensive trade network. But they didn't quite pull it off.
The Greeks came next in the story. Their first contribution was to make writing a core component of their culture. With a critical mass of people reading and writing, the extended sequential reasoning that writing made possible gave the Greeks new powers of reasoning, powers that they exploited vigorously.
We can't talk about Western Civ without discussing the Romans, and the sad fact is, they weren't very logical, either. They were too busy conquering the world to worry about things like logic. For example, Marcus Tullius Cicero, sometimes called "the greatest of the Romans", was certainly one of their best and brightest, but the notion of logical thinking was lost on him.
The Greeks and Romans did hold reason in high regard, but what they meant by 'reason' was altogether different from what we mean by it. Central to Greek and Roman thinking was the division of the human into body, mind, and soul. They saw these three as a hierarchy, with body at the bottom and soul on top. Thus, the ideal man paid no attention to bodily wants and paid full attention to the demands of the soul. The acme of this was the Roman soldier Mucius Scaevola. He was one of 300 Romans who had been chosen by lot to assassinate the Etruscan king, Porsenna, who was beseiging Rome at the time. Mucius screwed up and killed the king's secretary. He was caught and brought before the king, who threatened him with torture by burning if he did not reveal the Romans' plans. In response, Mucius thrust his right hand into a nearby fire without so much as flinching. Then he told Porsenna that there were 299 equally determined Romans sent to assassinate him. Porsenna, intimidated by the determination of the Romans and impressed with Mucius' courage, released him and raised the siege.
It was this contempt for bodily needs that animated the Romans and Greeks. It wasn't that they esteemed reason -- instead, they held emotional reactions (which they held to be 'bodily') in contempt. Thus, a 'reasonable Roman' would pay heed to omens, portents, and superstitions, because these were considered to be valid indicators of the real world.
The ancients' approach to religion is illuminating. As an extension of the natural history mental module, much ancient religion concentrated on understanding the universe and predicting its future behavior. The ethical dimensions of religion, and its role in personal spiritual development did not arise until later in history.
Another indicator of the nature of thinking in ancient civilization was the degree to which inconsistency was shunned. The record here is not impressive; the ancients didn't seem overly concerned with matters of consistency. This is another indicator of weak sequential processing. To put "2" from way over here and "2" from way over there together, and realize that they don't add up to "4", takes a logical perspicacity not appreciated by the ancients.
MILITARY THEORY
ABSTRACTION