Beginning to wrap my head arond the paleo program

The main argument for the paleo diet is, "The Paleo diet is good for you because paleolithic man ate like this and he did not die of lifestyle diseases such as cancer, diabetes or obesity. He ate this diet for 2.5 million years and it is what our bodies are genetically adapted to.  Agriculture started 10,000 years ago and our bodies, genetically speaking, have not had time to adapt to foods we created to feed our  larger populations.. ."  It is obvious to me that his active lifestyle and other factors could of played just as much of a role as diet in preventing these things.  The stronger argument for adopting a Paleo or Paleo-like diet is that the paleo mans CHILDREN did not have these diseases while ours have them in ever growing numbers.