We live in an age in which the majority of people blithely accept the suffering and death of aging as a given, an axiom, something of no great consequence to the arrangement of everyday life, and do much the same for the centralized control over lives and activities undertaken by a small, empowered elite. The latter is not a novel situation - see ancient Sparta, for example - but the sheer, pervasive breadth and depth in which it is presently practiced is an invention of the past few hundred years, made possible through great increases in wealth and technology. The Panopticon state is a modern creation, Sparta only its tiniest seed. Aging is aging, of course, and has been with us since the beginning. But both of these things are far from inconsequential, and indeed they shape our lives to a very great degree.
It is an important point that most people consider it unremarkable and entirely ethical to talk of regimenting society, placing widespread strictures on everyday activities and choices. Part of the struggle faced by researchers and advocates focused on lengthening human life stems from the fact that a large portion of the population sees nothing inherently wrong in forcing other people to act or not act as they see fit - or worse in forcing them to suffer and die to a timetable. It's somewhat irrelevant that the reasons for such would-be tyranny are flimsy and illogical. The real horror is that this is considered normal and reasonable.
Prompting this line of thought, earlier today I stumbled over an unusual argument against working to reverse degenerative aging and extend healthy life. At root it appears to suggest that a higher throughput of human lives is better (for nebulous reasons relating to variety of life and culture at any given moment), and since population will tend to fall off with increasing wealth and longevity we should thus refrain from trying to prevent the tremendous suffering and death caused by aging. As I was thinking what to make of this particular example, it occurred to me that in order to put forward this sort of argument, you really have to be very accepting of the present cost of aging: the pain, the death, the loss. It has to be a trivial axiom, something that isn't all that important, if you can focus instead on incrementally steering the variety of culture present in the world. Further, you would also have to be pretty comfortable with the sort of tyranny needed to force the world to relinquish biotechnology and die to a particular arbitrary schedule.
My most serious worry is about the lower total population of 90-150. 10 people wind up existing in 240 years, in contrast with 14 in 30-90. The reason this troubles me is not because I'm concerned about the four missing people. They are not harmed by not coming into existence. The reason why 30-90 seems better is because it has greater human richness. It's more diverse because four more people come into the world, and that diversity has advantages for the people who exist in that world.
Greater human diversity goes along with more intellectual and technological progress, or so it's been hypothesized by [diverse] authors. They hypothesize that the huge current population of the world is one reason why we are at a point of unprecedented development in many areas. More people means more specialization, more minds working on problems. The crucial thing here is not just how many people exist at a time, but how many exist over time. Arguably, 30-90 is better than 90-150 for the reason that more people are around to contribute to the human enterprise in 30-90 (though the same number exist at one moment in time).
It is an ongoing failure on our part that people can idly - or not so idly as has been the case in past years - make arguments of this nature without being noted as unethical, evil, and morally bankrupt. You can advocate enforcing the deaths of as many people as you like, and for whatever thin reasons, so long as they are old, or so it seems. Few people will think you any less of an upstanding fellow for doing so.