Are we facing self-extinction?
The threat to the Homo sapiens population has received less attention than other species. The possibility of self-extinction of Homo sapiens has been highlighted in several quarters (10), but dismissed by many. From an economic perspective, it is argued that a fertility rate between 1.48 and 1.78 is ideal in high-income countries, as labour immigration offsets the population decline (11, 12). However, this ignores the fact that the population of Homo sapiens is correspondingly reduced in the countries the immigrants emigrate from. It also overlooks the possibility that the low fertility rate might continue, leading to fewer fertile women in each generation. With a fertility rate of 1.4 in Norway, and assuming a 50–50 gender distribution, only 0.7 girls would be born per woman. If each of these girls also has 1.4 children, the next generation would have just 0.49 fertile women, and so it continues. The combination of a low fertility rate and fewer fertile women would, after a few generations, reduce Norway's population to less than one-third of its current size.
With a fertility rate of 1.4 in Norway, only 0.7 girls would be born per woman. If each of these girls also has 1.4 children, the next generation would have just 0.49 fertile women
Against the backdrop of the climate crisis, a reduction in the world population might be desirable and could even offer economic and environmental benefits. If the population were to be halved over a few generations, emissions would return to the level 100 years ago. The climate crisis would be resolved, and climate measures could be redirected to other areas. After that, the fertility rate could be increased to 2.1 to stabilise the population at a desired level.
However, developments have shown that this may be difficult. China's fertility rate is currently 1.2 due to its strict one-child policy and it is now experiencing a serious population decline. Two children have therefore been permitted since 2015, and Chinese women are now being encouraged to have three. Nevertheless, 30 % say they do not want more than one child, and the population decline has become a major political issue (13). Russia and Japan, with fertility rates of 1.4 and 1.3 respectively – and minimal immigration – are in the same situation.