David Runciman, writing about population decline, assumes that the population growth required to prevent human extinction (the ‘replacement rate’) is best described by the Malthusian formula ‘one couple = two children’ (LRB, 20 November). He may have in mind white, European, monogamous couple-based families, but in general human reproduction simultaneously requires much more and much less than a couple. On the one hand, conceiving and delivering a baby can involve more than two people (surrogate parents, sperm donors, online fertility supplement markets, the vast range of formal and informal institutions from fertility clinics to birthing and maternity wards, doulas and adoption regulators); on the other, it needn’t require a couple at all. More important, to think of reproduction rates as decided by the ratio of children to presumptive progenitors is misleading: humans are uniquely ill-equipped to survive without extensive networks of support at least until late infancy (and, as many parents of millennials and Gen-Zs will know, possibly much longer). In this sense, the replacement rate would be better defined as something like ‘approximately two people alive on Earth for every two people that were alive one generation prior’.

From this perspective, the picture begins to look very different. Not only is there no discernible threat of extinction of the human species as such, but the decline of population looks set to be governed by factors other than the rate of reproduction: wars and other forms of violence, drought and flooding caused by climate change, the collapse of food systems and so on. The picture looks more different still when we realise that when the term ‘replacement rate’ is used, it isn’t even to mean ‘for every two humans alive on the planet now, two humans alive a generation later’, but instead something like ‘for every two humans likely to rely on pensions or public health in x years’ time, two humans entering the labour force (and paying contributions) now’. If it takes a village to raise a child (or two), it takes a lot more to raise a taxpayer: usually, a nation-state or other territorially bounded political entity with a system of public collection, distribution and enforcement.

This is where the true parochialism of the ‘two for two’ formula becomes apparent. There are societies that do not value people only or primarily for their ability to engage in productive (waged) labour or provide reproductive (usually unpaid, or at least worse paid) care labour. These societies do not treat elderly members as a burden on the tax, public health and care systems; many Indigenous cultures of the Americas are examples of this, as is China. It is a feature of this increasingly violent phase of capitalism that elders are treated as a burden; there are modes of production, redistribution and exchange that do not require the increased extraction of labour power to justify maintaining or improving living standards for those outside the confines of state-sanctioned social reproduction.

One thing that Runciman infers correctly from the data is that, on the whole, people tend to reproduce less (if at all) once there is no pressure to do so. What the books he is reviewing seem to conclude is that people (and women in particular) should be persuaded otherwise. Even if we discount the horrid ways in which this is already happening – in the US, for example, not only in the states that have made abortion illegal, but also through the reduction of access to free, safe and universally available abortions – how about concluding that having children isn’t so great after all?

There would be nothing wrong with there being fewer humans, especially in the global North, whose population also tends to weigh heaviest on the environment. As degrowth theorists have argued for years, we need to produce and consume less. Unless we rapidly find a way to do that, we are likely to see massive population shrinkage anyway, but not of the voluntary sort. This, as we know, is likely to have the first and greatest impact on those least responsible for climate overshoot.