I first encountered this phrase when I worked alongside a solicitor from theproud city of Cork, in Ireland.
He was commenting on the suburb of choice of residence of a criminal: Sure they eat their own young there!"
I gathered it was run down, with few jobs and fewer open spaces and public money wasted or invested in amenities.
In another context we have all to some extent, eaten our children's future ...... Every time we borrow money we promise to invest now and repay later out of the proceeds of the investment. When this is regarded as a right and foist upon everyone as an "opportunity" then the odds are very high that there will be no proceeds in the future. A depression is created. Our children must survive impoverishment caused by bringing their future into our present. We enjoy their future investment opportunities now. We steal from them.