Principle 2:

“Our neural circuits were designed by Natural Selection to solve problems that our ancestors faced during our species' evolutionary history.”

In the meanwhile we have learnt that the brain has circuits, that these circuits were designed by Natural Selection to solve problems that our ancestors faced during our species' evolutionary history. This takes us back to the 19 th century, to the seminal work The Origin of Species , by Charles Darwin, published in 1859. A keyword in Darwin's work is “adaptation.” Adaptations are traits that help us in survival and reproduction. Let us look at an extract from The Origin of Species , at the definition of the principle of Natural Selection:

“Owing to this struggle for life, any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring ... I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection….”

According to Darwin, therefore, if there is any variation (whose cause may be anything) that would bring in a change that is profitable to an individual of any species, it will tend to the preservation of an individual, and second, will be inherited by its offspring, so that the individual survives because it preserves the variation which is profitable to it and secondly it is able to pass it on to its offspring. And this is the principle of Natural Selection.

Here we point to four important terms of the principle of Natural Selection. These are variation, inheritance, high rate of population and growth, differential survival and reproduction. It is important for us to understand differential survival which is distinguished from survival per se.