The Greek historian Polybius largely blamed the decline of the Hellenistic world on low fertility rates, writing his work The Histories that:
||“In our time all Greece was visited by a dearth of children and generally a decay of population, owing to which the cities were denuded of inhabitants, and a failure of productiveness resulted, though there were no long-continued wars or serious pestilences among us…. For this evil grew upon us rapidly, and without attracting attention, by our men becoming perverted to a passion for show and money and the pleasures of an idle life, and accordingly either not marrying at all, or, if they did marry, refusing to rear the children that were born, or at most one or two out of a great number, for the sake of leaving them well off or bringing them up in extravagant luxury.”
In a speech to Roman nobles, the Emperor Augustus commented on the low birthrates of the Roman elite:
||“How otherwise shall families continue? How can the commonwealth be preserved if we neither marry nor produce children? Surely you are not expecting some to spring up from the earth to succeed to your goods and to public affairs, as myths describe. It is neither pleasing to Heaven nor creditable that our race should cease and the name of Romans meet extinguishment in us, and the city be given up to foreigners,—Greek or even barbarians. We liberate slaves chiefly for the purpose of making out of them as many citizens as possible; we give our allies a share in the government that our numbers may increase: yet you, Romans of the original stock, including Quintii, Valerii, Iulli, are eager that your families and names at once shall perish with you.”
Upon the establishment of the Roman Empire, Emperor Augustus would introduce legislation to increase the birthrates of the Roman nobility.
From Wikipedia: https://en.wikipedia.org/wiki/Societal_collapse
Some believe that not only the Great Recession, but the Great Depression, may have been the result of a decline in birthrates overall. Clarence L. Barber, an economist at the University of Manitoba, pointed out how demand for housing in the US, for example, began to decline in 1926, due to a decline in ‘household formation’ (marriage), due, he believed, to the effects of World War I upon society. In early 1929, US housing demand declined precipitously. And, of course, the stock market crash followed in October of that same year.
Even though the overall world population continues to increase, it is more at the ‘back end’ than the ‘front end’ that this is occurring. That is, more people are kept alive than in the past due to improved nutrition, more refrigeration and better sanitation worldwide, as well as health care advances, from vaccines to antibiotics, and many other advances in medications and in different improvements in health care. Certainly, in advanced nations, few groups would be considered to be “breeding like rabbits”. The ‘baby boom’ (1946–1964) in the US, was likely, if Barber’s contentions are correct, more of a return to birthrates closer to historical norms, like those of the first decade of the 20th century (but the ‘baby boom’ of 1946–1964 were still lower than the 1900–1910 period), with birth dearths both before and since making the so-called “baby boom” appear so big.
From Wikipedia: https://en.wikipedia.org/wiki/Sub-replacement_fertility#Historical_effects