Natural selection means for the most part a struggle ensuring the death of the weak and the 'unfit.' The survival of the fittest means that those creatures survive who are best adapted to all their circumstances, whether these are favourable or unfavourable to the maintenance of a high standard of living. That 'nature' may carry out selection it is necessary that there shall be no outside interference, say of man, able to stave off death, whether of the individual or of the race. Death, you see, is the protagonist in this biological play, or rather the mainspring of the machine. And, undoubtedly, death is not only conspicuous in nature but is of profound significance for life. Is it or is it not also of value in a sense surpassing that which the biologist acknowledges? Ought we to look upon it as the enemy or as the friend of life?
One thing is plain. Those men of science who saw it as protagonist were right in thinking that by the death, that is, by the natural selection, of the unfit from among the fit, the survival of useful variations may be assisted. Death, of course, cannot have anything to do directly with the originating of better lives (that is of better accommodated lives), but once they have come into being it can help to keep them in the ascendant as begetters of their kind. Natural selection has its use—shall we say its value?—for the advance of life.
Need we be surprised at this, we who have a more than scientific sense of values and have discovered purpose? Need we be surprised to find death a friend to life, seeing it everywhere? Matter is life's friend as well as means and hindrance. So too is death.
Let us consider the beginning of death on the earth; that is, of natural, not of merely accidental death. For it had a beginning, not coeval with the coming of life. There are living creatures now who normally escape it, who die only by accident, are, in fact, if they die, always killed. There are creatures alive now whose years are to be numbered by thousands upon thousands upon thousands, yet who have never grown old. The Pyramids of Egypt are of yesterday compared with the amoeba in the nearest pond.
The manner of life of a one-celled creature is this: it grows, and when it has grown to a size presumably inconvenient it divides into two creatures, both of which, obviously, are the same age. The creature itself becomes two instead of remaining one. The two creatures who were one repeat the process and become four. The four become eight and so on to the end of the earth. None die naturally, and when or if the end of the earth and of themselves is reached they will all be killed and every one of them will be of the same age; but none will be aged. They will be cut off, these naturally immortal creatures, in unimpaired maturity and the perfection of their structure and functions. But, you observe, if life on earth had not passed beyond the one-celled condition it would never, to our minds (if our minds could have been arrived at in some other sphere), have been worth living. All the potency and promise of life which have slowly been revealed through the improvement of its creaturely medium would have remained hidden behind the screen of those immortal jellies. Life began to create a new engine of advance when cell and cell were built up together, and the many-celled creatures started on their mortal and masterful career. For, note, the aggregation of cells in an organized body precludes their individual immortality. They become differentiated and associated for special purposes and they lose the opportunity of preserving life by continuous division. They are mutually imprisoning, they grow old, in time they die—they must die. Life, in beginning this advance, embraced inevitable death. Death, if you like, is the price—if indeed it should be counted a price and not a boon—that we pay for freedom to live as what we are and to become what we shall be. The immortal amoeba is after all a slave. It is this creature that manifestly pays a price, one at which no man of us would buy immunity from death.