In measuring the dimensions of space we have to start from some fixed standard, such as the foot or yard, taken originally from the experience of our ordinary senses and capable of accurate verification. From this we arrive by successive inductions at the size of the earth, the distance of the sun, moon, and planets, and finally at the parallax of the fixed stars. So in speculations as to the origin and evolution of the human race, history affords the standard from which we start, through the successive stages of prehistoric, neolithic, and palæolithic man, until we pass into the wider ranges of geological time. Any error in the original standard becomes magnified indefinitely, whether in space or time, as we extend our researches backwards into remoter regions. Thus whether the authentic records of history extend only for some 4500 years backwards from the present time to the scriptural date of Noah's flood, as was universally assumed to be the case until quite recently; or whether Egyptian and Chaldæan records carry us back for 7000 years, and show us then a dense population, powerful empires, large cities, and generally a highly advanced civilization already existing, makes a wonderful difference in the standpoint from which we view the course of human evolution. To begin with, a short date necessitates supernatural interferences. It is quite impossible that if man and all animal life were created only about 4000 years B.C., and were then all destroyed save the few pairs saved in Noah's ark, and made a fresh start from a single centre some 1500 years later, there can be any truth in Darwin's theory of evolution. We know for a certainty from the concurrent testimony of all history, and from Egyptian monuments, that the different races of men and animals were in existence 5000 years ago as they are at the present day; and that no fresh creations or marked changes of type have taken place during that period. If then all these types, and all the different races and nations of men, sprung up in the interval of less than 1000 years, which is the longest that can by any possibility be allowed between the Biblical date of the Deluge and the clash of the mighty monarchies of Assyria and Egypt in Palestine, the date of which is proved both by the Bible and by profane historians, it is obviously impossible that such a state of things could have been brought about by natural causes. But if authentic historical records carry us back not for 3000 or 4000, but for 6000 or 7000 years, and then show no trace of a beginning, the case is altered, and we may assume an almost unlimited duration of time, through historical, prehistoric, neolithic, and palæolithic ages, during which evolution may have operated. It is of the first importance therefore to inquire what these records really teach in the light of modern research, and what is the evidence for the longer dates which are now generally accepted.