A few years ago, I read a couple books by geneticist Bryan Sykes. The one that was the most fun was mostly about the population genetics of the British Isles but looked at the whole of Europe and just a little on the remainder of the planet. It was an explanation of the genetic relationships of the British to each other and what could be determined about where the groups came from. As I say, it was fun.
I believe that Sykes is working on something for North America. That seems a little frightening - given some of our problems over the more recent centuries.
Anyway, Sykes talks a little about population "bottlenecks" and how much more common these were in Europe, than elsewhere. Now and then, the Europeans had some tough times. The small number of ancestors - well, their genes - show up in the genetics of today's populations.
A percent of a whole might just be pulled from a hat, perhaps 5%. That percent could be associated with a fairly large resource share. Let's say 25% of the world's resources. Then, if a 5% of the human population could be found using 25% of the world's resources perhaps that would indicate an natural efficiency that warrants the 5% controlling a larger percentage of the world's resources. The earth might return to a pristine state if, say an even smaller slice of humanity controlled more resources.
I once read a sci-fi book where the entire population of the planet was something like 9. Not surprisingly, 1 of these people often tried to kill himself out of some sense of despair but the other 8 were highly resourceful so they would revive him. They probably just appreciated the drama that he brought to their existence.
If we use World Bank numbers: about 80% of the world's population lives on less than $10/day. World population of nearly 7 billion. That is 5.6 billion people. The 2008 Farm Bill sets US food aid at $450 million/year. The UN's World Food Program provides $1.25 billion/year. If all that food aid is distributed to those 5.6 billion people - they are getting about 31 cents . . . per year in food. Let's say it only goes to 10% of those people living on $10 a day. Then, each of those "poorest of the poor" would have $3 of food from the US & UN each year.
Obviously, some other means than cutting off food aid would have to be arranged for a depopulation of the world's poor.
Steve