Did the Human Brain evolve to solve complex problems

The New Scientist of 26th May included an article entitles The Argumentative Ape contains some interesting ideas about persuasion but but I am unsure about the foundations of the article and as a result I have posted the following comment after the article on the New Scientist site:

While a number of good points are raised in this article about group interaction I feel it is based on a flawed assumption when it says about the brain:

Why did we evolve such an apparently flawed instrument? Our irrational nature is very difficult to explain if you maintain that human intelligence evolved to solve complex problems, where clear, logical thought should offer the advantage. As such, it has remained something of a puzzle.

But did human intelligence evolved to solve complex problems, or do we simply have an animal brain which has been enlarged in various ways to be able to process large volumes of information, using the same simple logic circuits? This would provide a simple explanation of the so-called "flaws" 

A new-born animal arrives knowing nothing about the world and has to build what is an inevitably an incomplete and fuzzy model of the world in which it lives. The difference with humans is that once a rudimentary language has reached a certain level the most evolutionary effective way for a child to learn is to accept what its parents tell as correct without question, which explains the way children suddenly start learning like a sponge once they have conquered the elements of language.

Social groups which pass on the most effective life skills to children in this way are more likely to be successful, even if they also pass on some suppositions about the world which are actually unsound, but not actually dangerous. It is only a small step further to assume that individuals who appear to be particularly authoritative are more likely to be considered purveyors of “reliable” information. Of course as a child gets older its rate of learning drops and it starts to be more questioning of authority, to an extent which can vary from rebellious to subservient.

Taking this view, our brain has evolved to handle fuzzy and incomplete information and the question is not why the brain is flawed – but rather how a simple brain learns to handle more formal matters. But we teach subject such as formal logic and mathematics in school because they are not natural skills, and this approach suggests that there is nothing to indicative that our brains work in a significantly different way to animals once you allow for the differences in brain size  and the ability to be taught using language.