Yes, but how do the other 4 billion humans "go away" without civilization grinding to a halt from the process?

Will we all have to follow China's policy of one child per family? Enforced euthenasia for the elderly and infirm? You can see the slight problems there, I am sure.

One thing is certain: Humanity cannot keep at its current level of population growth and resource consumption while remaining on one planet that is not expanding and adding new materials without something giving way. Will we survive the changes and still remain civilized and human? Or will something else take over from the world we have left?