Something like a stable balance between human numbers and resources may then begin to define itself.

In any effort to understand what lies ahead, as much as what lies behind, the role of infectious disease cannot properly be left out of consideration. Ingenuity, knowledge, and organization alter but cannot cancel humanity's vulnerability to invasion by parasitic forms of life. Infectious disease which antedated the emergence of humankind will last as long as humanity itself, and will surely remain, as it has been hitherto, one of the fundamental parameters and determinants of human history.

...the galloping increase of human numbers practically guarantees that existing margins between food supplies and human hunger will swiftly disappear, leaving less and less in reserve for times of unusual crisis.

...it now requires an act of imagination to understand what infectious disease formerly meant to humankind, or even to our own grandfathers.

It is obvious that human (and non-human) diseases are evolving with an unusual rapidity simply because changes in our behaviour facilitate cross-fertilization of different strains of germs as never before, while an unending flow of new medicines (and pesticides) also present infectious organisms with rigorous, changing challenges to their survival.

Nonetheless, the way infectious diseases have begun to come back shows that we remain caught in the web of life - permanently and irretrievably- no matter how clever we are at altering what we do not like, or how successful we become at displacing other species.