Along with decreasing doubling times as a function of increasing rates of population growth over the past several thousand years, the human species has shown striking parallels with a malignant growth. Some cancers also display decreasing doubling times of cell proliferation during the most rapidly growing phase. At 6 billion, the number of doublings reached by the human population as of 1998 is 32.5, with the 33rd doubling (8.59 billion) expected early in the next century. In terms of total animal biomass, including that of domestic animals under human control, the 33rd doubling of human-related biomass has been passed. In terms of energy use, which is a more accurate, index of the global ecological impact of humans, the human species has passed its 36th doubling. These calculations are important because, in addition to the number of doublings, the human population is showing several important similarities with a malignant organismic tumor, which results in death of the host organism at between 37 and 40 doublings. At current growth rates, the number of individual humans will reach those levels within 200–400 years from the present, but the ecological impact will be felt much sooner since the number of doublings of energy consumed will pass 37 early in the next century. These observations support the hypothesis that the human species has become a malignant process on the planet that is likely to result in the equivalent, for humans, of ecosystem death, or at least in a radical transformation of the ecosystem, the early phases of which are being observed.