How did we get big brains?

In the book we explore the ideas that socialisation and dealing with gravity were some of the selective pressures that helped trigger an increase in the size of the brain. It is a useful question if we add the ideas that 'junk in equals junk out' and a big brain is essential to becoming conscious. The brain is an information processing device that needs good input to function. So understanding that certain inputs were critical to the development of the brain, both in evolution and in growing up, helps us choose pathways to stimulate those inputs to improve the functioning of the brain in the adult. http://www.guardian.co.uk/technology/2010/mar/28/colin-blakemore-how-human-brains-got-bigger The above  article dismisses the idea that there was gradual development in the brain due to selective pressures. The argument that stimulating pathways that deal with gravity and socialisation helps improve the brain function in the adult does not necessarily need an evolutionary basis for it to be valid, but I have always liked it as an explanation. If Blakemore is correct I will have to let go of that. Hey ho.