The fixation with N, the size of the human system is absurd, when for all practical purposes the two attributes that really matter are i) the impact of each in

The fixation with N, the size of the human system is absurd, when for all practical purposes the two attributes that really matter are i) the impact of each individual on the biosphere (human - external interactions, or h-e) and its long term biophysical stability and ii) the internal relations of individuals (human - human interactions, h-h, also known as economics, politics etc.) and its long term socioeconomic stability Alarmism regarding either over or under population usually has hidden agendas and unspoken assumptions as to what is desired state of the human system and the stability or continuation of certain past and current arrangements, the dominance of certain tribes over others etc. What complicates the discussion is the enormous unevenness in the distribution of both important factors mentioned above and the resulting wealth and quality-of-life gradients across the planet. In turn this results from the (relatively) slow timescale of technological diffusion which involves complex cultural phenomena and conflicts. A cursory discussion of the intricate web of social dynamics, dependencies and inequalities and how they affect "N". When people complain about how "expensive" it is to raise kids we need to recognize the changing meaning of "raising kids": from the pool of cheap labor that this was historically, to the growing amount of individual attention lavished on kids in the developed world today. Yet that attention requires societal resources. Between parents, various providers and (potentially) a subsidy from the commons some economic equilibrium must be found. On the other hand why would economically active parents not be able to "afford" raising kids to the available and desired standard? One factor (among many) might be that their own economic output is devalued as a result of others doing the same work while aspiring to a lower standard of living. Back to the question of optimal N. In a sustainable global economy (conditioning on meeting the h-e, h-h challenges to an adequate degree) I suspect that N is actually irrelevant within a very broad range. In a sense the attention we pay to population numbers is a measure of how primitive our societies.