Although several ecological and demographical arguments hint at the existence of a relevant time delay between the deteriorating action of human population growth on the natural life support system and the reaction of growth-limitating regulatory mechanisms, this notion has not been considered in population models so far. We show that global population growth can be simulated by a hyperlogistic time-delay equation. This model allows a simulated population to exceed the carrying capacity K for a limited period, falling below it subsequently. It is analyzed and compared to other population models. The parameters of the function--the "intrinsic rate of natural increase" r, the "carrying capacity" K and the time delay T--are evaluated by fitting them to the historic data of world population. In a sensitivity analysis those data where varied within the interval of their possible values. Whereas only one solution or r appears, a one-dimensional manifold of T-and K-values can be found, which provide equally good fits. This makes it impossible to exclude the existence of a time delay mathematically. Since a delay of one or two decades is sufficient to cause an overshoot and subsequent collapse of world population, there is no reason to trust in self-regulatory mechanisms in human population dynamics.
I" This work formedpart of the requi.rements for a masters degree. ~; Current address: Osterreichisches Okologie-lnstitut, Seidengasse 13, A-1070 Wien.