Incidentally, it is not absurd to class this ecological role of humankind in its relationship to other life forms as a disease. Ever since language allowed human cultural evolution to impinge upon age-old processes of biological evolution, humankind has been in a position to upset older balances of nature in quite the same fashion that disease upsets the natural balance within a host's body. ... Sooner or later, and always within a span of time that remained minuscule in comparison with the standards of biological evolution, humanity discovered new techniques allowing fresh exploitation of hitherto inaccessible resources, thereby renewing or intensifying damage to other forms of life. Looked at from the point of view of other organisms, humankind therefore resembles an acute epidemic disease, whose occasional lapses into less virulent forms of behavior have never yet sufficed to permit any really stable, chronic relationship to establish itself.
- Plagues and Peoples, William McNeill, 1976, pg. 22.
