Not meaning to be picky Hoggy but stone age man wasn't our cousins
they are our ancestors

I understand what you are trying to say comparing paeolithic to neolithic
man and physical strength etc but nature gave us an adaptive brain and
developing agriculture was part of our natural evolution.Nature gave us
the ability to develop and evolve.
As for cancers not being prevalent in the stone age,you can put
this down to the fact that man didn't live much past our physical
peak which is around thirty and most cases of cancer occur in people
older than this
We are definitely better off today matey,i will take our current lifestyle
over the previous which must of been for the most part a hard and miserable
existence.