This graph of European urban population over history shows some dramatic declines, suggesting that there may have been historical analogue to our upcoming world population decline. And there have long been rumors that at least elites often had low fertility. Searching for quotes, I’ve found these:
Classical literary sources, tombstone inscriptions and skeletal remains have been used by classicists to show that there was probably a decline in the population of the Roman Empire caused by the deliberate control of family numbers through contraception, infanticide, and child exposure.…
If the modern fertility transition … is not unique, then its most likely predecessors were probably found in the classical period, especially in Ancient Rome, or in Soong China or Tokugawa Japan. …Â
Where the literary evidence is strongest is that there was a significant restriction of legitimate fertility in upper-class society [in ancient Rome]. That there was such a phenomenon is given greater strength by agreement, both ancient and modern, on why it should have taken place, namely fear of dividing the family patrimony among the heirs, so inevitably demoting them and their children down the social and economic ladders. This would have meant one section of the society exhibiting long-term but probably stable lower fertility.
This may not have been a rare phenomenon in history. It may well have been the situation among the Genevese bourgeoisie in the eighteenth century. It may have been the situation in France that resulted from the equal inheritance promoted by the revolutionary army and the statutes of the Code Napoleón, a phenomenon possibly misinterpreted because the French fertility decline was caught up by the emerging global fertility transition induced by the Industrial Revolution. (more)
Europeans report[ing] on Asian infanticide … were surprised that infanticide occurred not only within marriage but among the rich as well as the poor. … Infanticide, even when not proscribed, usually had an element of secrecy, … Bangladesh … mortality rates showed a preference for a family consisting of two sons and one daughter. … East India Company officials noted with surprise that infanticide in India was practised not by the poor but by the rich …
Family pride was, and is, strongly associated with the ability to pay cripplingly high dowries. … All this is propelled by … aim of subcastes to be seen to behave as higher subcastes, … In the top rungs of these castes the daughters could not marry higher and so the only way to avoid the degrading shame of having a postpubertal unmarried daughter in the family was to kill her at birth. The East India Company’s reports recorded such subclans as claiming that no daughter had been raised for generations. …Â
Tokugawa [Japan] near-stationary population was achieved with lower marital fertility but higher marriage levels than in England at the same time. Lower marital fertility was partly attained by infanticide, although this was probably practised mostly in families with above-average fertility or below-average child mortality. It probably ensured a lower level of difficulty over land inheritance and fewer other siblings seeking work off the family farm and outside agriculture. …
From his field work on the lower Yangtze in 1936, spoke of infanticide being common at that time especially when small landholders were faced with the problem of land division. … The evidence is clear that the main fear in having too many sons was the division of the land in a male partible inheritance system to the point where the sons cannot grow enough food for their families’ needs. … Sons beyond the second were so disadvantageous that they were often given away; …
The expanding West with its denial of the right to kill a child was deeply shocked on encountering large-scale [Asian] infanticide.… decision to kill is usually made by the father, … women are more likely to reveal what happens, partly because many are aggrieved. The act is nearly always carried out by women. …
There is usually a desire to improve one’s situation or that of the family or to ensure that one’s descendants are not poorer. Female infanticide was greatest among the richest in eighteenth-century and nineteenth-century India. …
Situation was identical among the middle class in ancient Rome and probably among the late eighteenth-century and nineteenth- century French peasantry. The lowest subcastes in India’s hypergamous castes could not afford dowry for the marriages of more than one daughter. (more)
Many of these examples seem to correlate with resource limitations. In an agrarian society, if the amount of land is limited, increasing population leads to privation. This may be expressed in terms of not wanting to divide land to maintain status, but if there are more people on the same amount of land, with static technology, they will all be poorer and eventually starve. Describing this as a fundamentally social process rather than a social response to resource constraints seems like a reach.
Modern technological societies are built on childhood education. This puts economic stress on parents, both because education itself is expensive and because children are no longer a source of income. Such societies also use the production of women, reducing the amount of time women can devote to childrearing, further increasing the downward pressure on fertility. All of this would be true, regardless of social norms, so it seems odd to claim that social norms drive this, in preference to this being the social response to changing conditions.
Beyond that, at least some of the concern over this trend comes from a belief that unless the workforce keeps growing, technology will stagnate and progress will cease. If that is the case, however, removing women from the workforce in order to increase fertility would have the same effect.
My own expectation is that we will find a series of technological improvements (increased longevity, more efficient fertility and childrearing, improved allocation of resources) that will stabilize the population and maintain technological (defined broadly) progress. Whether population increases at that point will probably depend on how well we have addressed the other needs (land, waste, and energy) that constrain human population.
You should take a look at Augustus’s Moral Laws (Lex Julia). He’s often described as a devout social conservative (aristocratic, traditional Roman virtue and family structure), and the laws lend credence to that. They offer a glimpse of what Augustus thought had changed amongst his peers. They don’t seem to have worked in the long run (which is informative if we’re thinking about where to make the changes), and many were repealed soon after his death.