This is probably a political issue in the minds of many, but I'm not sure you need science to establish the fact there are too many folks. Just look around you!
Seriously though, I don't agree with forced sterilization. In the end, people must be free to make choices concerning their own lives, and such talk is frighteningly remindful of the Nazis.
I am going to venture that the man who sat on the ground in his tipi meditating on life and its meaning, accepting the kinship of all creatures, and acknowledging unity with the universe of things, was infusing into his being the true essence of civilization.
Chief Luther Standing Bear
"Protest is when I say this does not please me. Resistance is when I ensure what does not please me occurs no more."
Illegitimi Non Carborundum