All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
The small family is the path to social, but not evolutionary, success for offspring
Last reviewed: 01.07.2025
One of the foundations of evolution is natural selection. The larger the population of a particular animal species, the better this selection should be.
It is logical that in this case, a large number of offspring is an important condition for successful evolution. However, in industrialized human society, the growth of human well-being is inextricably linked with a conscious limitation of family size. This dependence in the middle of the last century was called the "demographic transition" (from a traditional society to a modern one).
According to the popular "adaptive" theory, the demographic transition is beneficial to evolutionary processes in the long run, since low fertility increases the wealth of descendants, who should eventually reach a level of wealth that allows for more children in modern societies.
Researchers from the London School of Hygiene and Tropical Medicine, University College London and Stockholm University disagree with this theory. They confirm that a small number of children contributes to the subsequent economic success and high social status of descendants, but they claim that their numbers decrease. The scientists conclude that the decision to limit family size can contribute to the improvement of the economic and social status of descendants, but socioeconomic success does not always lead to evolutionary success.
The study highlights the conflict in modern society between socio-economic and biological (evolutionary) success, whereas in traditional society, behavior that leads to high social status and well-being usually also implies large numbers of offspring.
For their research, the scientists used data on 14 thousand people who were born in Sweden at the beginning of the 20th century, and on all their offspring to this day.
The researchers determined the socioeconomic success of these people using indicators such as school success, higher education, and overall family income.
Reproductive success was measured by the number of individuals surviving to adulthood, marrying before age 40, and having offspring up to 2009.
It turned out that a smaller family size in the first generation under study and a smaller number of children in subsequent generations are indeed associated with a better socioeconomic status of the descendants. However, contrary to the adaptive hypothesis, the influence of a small family size and high well-being on the reproductive success of subsequent generations either did not have any effect at all, or this influence was negative.
[