The time at which the evolution of man took place is very well fixed. Scientists are almost unanimous in placing the first steps prior to the glacial times during a very long period, some even going to the extreme of giving 600,000 years to the eolithic or protolithic stage higher than the pithecanthropus or ape-man. They are also almost unanimous in opinion that the first sure evidence of a creature we can call man occurs in the earliest glacial epoch, and the estimates vary as to how long ago that was, but it is generally believed that it was at least 250,000 years. It is safe, then, to state that it is not very far from a million years since the first steps from the anthropoid to man. In this pliocene time a tropical climate extended throughout Europe, but it grew colder and colder, and furnished the very conditions of a severe environment necessary to kill off the least intelligent and to evolve a brainy man by natural selection.
* The Malay Archipelago.
* Science, February 28, 1902.
There is a current delusion that man was evolved in an environment where life was easy and the climate warm. It is amazing that many scientists hold this view, scientists, too, who know that such a condition could not possibly eliminate the stupid and select the most intelligent. If Africa could have evolved man, the gorillas would not exist there now, for they would long ago have changed into higher types. Nevertheless Africa is very commonly assumed to be the cradle of the race.
Though the Scandinavian ice cap did not extend into Asia, that continent had a cold period also; indeed, we are still finding the frozen carcasses of mammoths imprisoned in the ice of Siberia at this time. The difficulty or impossibility of traveling south over the Hindoo Koosh and other ice-clad mountains, no doubt imprisoned the Eastern type so that evolution occurred at the same time it did in Europe. The geology of Asia points to excessive submergence in glacial times when Europe probably was elevated. The central plateau would then have been insular, and a gradually increasing severity of climate would have produced the severe conditions necessary for human evolution, just as in Europe.
In 1881, August Weismann showed that duration of life was dependent upon the needs of the species,* and that sometimes species could not survive unless the individuals died early - even immediately after egg laying in some cases - and that sometimes when enemies were numerous and slow breeding more advantageous long life was essential, or the species would have perished. Man being in the latter class it rather indicates that his environment was so severe that a large number of offspring was at one time a necessity if two were to survive and raise offspring of their own. He had to live long to do this. This is another form of the law that need of the species is sometimes paramount to the need of the individual in the struggle for existence.
* Essay read before Association of German Naturalists at Salzberg.
We must not confuse maximum length of life with average length of life. In the early savage life, the latter was probably not more than five or ten years on account of the mortality among children, and it is still less than fifteen years in the Philippines, even with large birth rates. Maximum years or period of senility on the other hand, is a result of the above law, and the fact that man was a slow breeder, having but one offspring every year or two. The only surviving lines were those that lived long enough - natural selection of those whose long life permitted the most offspring. This evolution had really been finished before high civilization began, because our earliest records show that three score and ten was the maximum. There has been no change in age of senility since. As procreation usually goes on until old age, forty-five must have been old age once, and the other twenty-five years have been added by civilization. Primitive man, like all other animals, never died a natural death. All present wild animals die violent deaths, at the hands of enemies or of starvation, and few, if any, ever reach the senile period, though they can live into this period if we take care of them as we care for our old people. Likewise, savage man could have lived into his senile period if cared for, but as he could not be thus looked after he had to die, and probably forty was the limit. Man's length of life, then, is a remote result of the struggle for existence due to overpopulation in his early evolution.