The kind of population pressures and ecosystem destruction that humans are now wreaking upon the body of the Earth, are exactly analogous to the excessive multiplication of cells and systemic malignancy that are recognized in medicine as a cancer tumour: both are proliferative disorders characterized by uncontrolled growth; both tend to spread throughout the "body" of the organism; both exert pressure on adjacent "tissue"; both continue to grow even under extremely crowded conditions; both produce chemicals that have negative effects on remote regions of the organism; both generate new vessels to support their growth; both fail to "differentiate" in form and function. It is no exaggeration to say that humans have become a plague upon the Earth.