Gives a persuasive answer to a difficult question
This interesting book is not about how to avoid ageing or about how to grow old gracefully, etc. Instead Austad is concerned quite simply, as his title says, in why we age.
The argument that he develops from evolutionary biology is very subtle, but persuasive and profound. It's not that the ageing of individuals is good for the species. That's a fallacy, although it works that way. And it is not because of limited cell division. That too is an effect. Rather it is because evolution does not support system maintenance past the age of reproduction. In other words (this is a slippery, but nonetheless cogent and persuasive argument) no gene that either maintains the system or tears down the system or even just leaves the system as it is past reproductive age is selected. None are selected. All post-reproductive age mechanisms are instead randomly selected; that is, selected by accident. Since there is the second law of thermodynamics, or entropy, a random system will just run down. It will go to chaos; and for our bodies, that means breakdown. Simple as that.
Still, the question remains, why don't we continue to reproduce as we grow older? Or, why isn't our reproductive age unlimited? The answer is subtle: such a system wouldn't work because it would be static and couldn't change with the environment. The old reproducers would, through the strength of their experience and position, control reproduction and naturally work against change. Consequently, they would drift away from their changing environment and become less fit. Also, the faster an environment changes the faster the species must adjust; therefore, reproduction at an earlier and earlier age would be selected for, consistent with the ability to gain subsistence. As is noted here and elsewhere, it is a melancholy fact that we age and die because of sexuality. Sexual reproduction only works if the young have a better chance at reproducing than the old. It should be realized that someone a generation younger is, paradoxically, a generation older in terms of genetic experience. The gene pool has mixed one more time. The young can only have the advantage if the experienced and powerful get old, weak and die. And so we do.
--Dennis Littrell, author of the mystery novel, “Teddy and Teri”