Evolution, however, is not driven strictly or solely from needs for survival. That has an impact, yes, but realize... Evolution is driven by increased reproductive fitness. That term, reproductive fitness, refers to the ability of an individual to pass its genes on to another generation.
If people who used symbolic thought (language, counting, pictures, etc) managed to increase their reproductive fitness (that is, get more of their genes into the next generation and beyond) then that would mean the genes for those traits would survive and multiply.
I think I see what you are saying, but I politely disagree. Every evidence that comes to mind regarding evolution is that environmental pressures play on the genetics (epi-genetics) causing adaptations, and only over time do these adaptations (presumably) cause speciation.
Reproduction has little to do with how a human brain functions. Indeed, the old adage is that a man's thinking turns from his big head to his little head with next to no reasoning at all.
There is a point in the not all so distant past where humans crossed a line and began utilizing symbolic reasoning. That symbolic reasoning is now so pervasive we have difficulty seeing how it was prior. We right now are communicating by symbolic reasoning and symbolic thought. It must be taught. Once taught, we tend to forget how we reasoned previously, dismissing it as the thoughts of a child.
Speech (and song) are natural in that other animals communicate by making sounds, recognizable to each other. So human speech of itself isn't an indicator. But writing is an indicator of symbolic thought; every letter is a symbol, every ideogram is a symbol, every numeral is a symbol. There is no environmental pressure that can bring about symbols and symbolic thought. The symbols are not the thing they represent.
The explosion of thought in Mesopotamia just after the Ice Age and humans incorporating grain into their diet (bread, beer) and as cattle feed, spurred such an exponential growth in cumulative "knowledge" that has yet to be matched. We come pretty close with this past century, but in a very short span of time by evolution standards, humans developed mathematics, writing, astronomy, construction of walled cities, pottery, textiles, the wheel, and weaponry. This was at the end of the Stone Age and the beginning of the use of certain softer metals like copper and tin. All of this took place in a comparatively short span of time - without any evident environmental pressure.
The presumption has always been that the opioids in grain affected the human brain. Humans did not evolve to consume grain, we are not ruminants. Indeed, a very common human allergy is to grain.
This is why I have long viewed the Adam and Eve / Tree of Knowledge story as an allegory for the "opening of the mind" brought on by the agricultural revolution. At some point humanity crossed a line into "knowing they were naked." Previously they didn't care, because they still thought and functioned solely as animals. With the advent of a grain diet and the transitions brought about developing symbolic thought and reasoning, whole new vistas of intelligence opened up. But none of this was due to environmental pressures, it was either a happy accident or there was some deliberate external nudge.
