Before speculating on what might happen in the future, it is well to recollect what has happened in the past. The earth has been inhabited for thousands of years, and modern research has revealed the remains of many ancient civilisations that have perished. For example, there were the great nations of Cambodia and of Guatemala. In Crete, about 2000 B.C., there existed a civilisation where women were dressed as are this evening the women of London and Paris. That civilisation perished, and even its language cannot now be deciphered. Why did these civilisations perish? Surely this momentous question should take precedence over barren discussions as to whether there will be sufficient food on the land or in the sea for the inhabitants of the world in 200 years' time. How came it about that these ancient nations did not double their numbers every fifty years and fill up the earth long ago? The answer is that they were overcome and annihilated by the incidence of one or other of two dangers that threaten every civilisation, including our own. These dangers are certain physical and moral catastrophes, against which there is only one form of natural insurance, namely, a birth-rate that adequately exceeds the death-rate. They help to illustrate further the fallacy of the overpopulation scare. The following is a general outline of these dangers, and in a later chapter (p. 70)(see [Reference: Dangers]) I shall quote an example of how they have operated in the past. Section 9. PHYSICAL CATASTROPHES Deaths from famine, floods, earthquakes, and volcanic eruptions are confined to comparatively small areas, and the two physical catastrophes that may seriously threaten a civilisation may be reduced to endemic disease and war. (a) _Disease_