If evolution has taught us anything, it is that favourable survival characteristics are perpetuated and non-favourable characteristics are eradicated. Applying this to the development of 21st century humans, it has been well documented that our progression from the earliest ancestral hominoid beginnings of homo habilis through homo erectus, homo neanderthales and homo sapiens was accompanied by an ever-increasing brain size.
Our human evolutionary separation began when we were forced to adapt to our changing landscape in our basic needs for survival and in our efforts to gain knowledge of the world in which we inhabited, we accelerated the encoding of proven genetic advancements in our DNA in order for successive generations to build upon.
Indeed, over the millennia humans have subconsciously continued to exploit slight favourable evolutionary characteristics, and enhanced both physical and mental skills to continually learn more about the environment in which they inhabited, and how they could exploit these advantages within the need for survival.
It is easy to suggest that the waves of successive human evolutionary advancements have always been gained through an increase in knowledge and have therefore simply come about through an ability to encode this increase in the knowledge gained over time within our successive cultures and societies. There is a strong case to show that as this knowledge became more complex, it acted as an evolutionary stimulus so as to develop an increasingly complex social structure to first encode, and subsequently to exploit this knowledge.
Alternatively, there is a large catalogue of physical anomalies that have left their indelible mark on the human form and just a cursory glance can shed light on a previous time in our history a tailbone tells of a time when human ancestors possessed a tail and inhabited trees and an extraneous appendix that was used to secrete enzymes into our digestive system in order to break down the grass that was part of our diet. The slow removal of these previously evolutionary favourable components within the human form show us that when things are not needed they are removed over the successive generations, however this is certainly not true for the brain.
As part of the human form, the brain is our most important organ with its influence over every process that occurs, in order to maintain the balance of life. It controls what we do and how we do it, and the success of its function is dependant on the energy it receives, and its ability to deliver the myriad of various messages to different parts of the body. The more complex the processes which the brain is asked to carry out and the speed at which they must be completed requires a large proportion of the energy being consumed by the body. Ally this to the fact that the majority of these processes are completed on a subconscious level and occur without specific instruction from the conscious, a picture can be developed of how vital the brain is.
The brain is encased in the strongest bone structure which itself has adapted over the species to provide the relevant protection to the most important internal organ and throughout this adaptation has directed the other major organs of the lungs and heart to draw the energy source of blood through the largest artery in the body.
All of this evidence points to the belief that the majority of what we possess as a human and what is contained within the 21st century human form is evolutionary favourable. If we apply this to the question in hand, it would seem an evolutionary backward step to have a brain that was 900% too large, contained in a part of the human form that is vulnerable, relatively heavy, requires a large component of blood and demands a high proportion of chemical energy. There is little or no evidence to suggest that any part of the brain is superfluous and therefore the only conclusion is that humans use if not all then most of our brains. Perhaps the question may be bound in the fact that we can merely access 10% of our brains at any one time thereby asking a question that may serve a more useful purpose.
