One of the foundations of evolution is natural selection. The larger the population of a particular animal species, the more qualitative this selection should be.
It is logical that in this case a large offspring is an important condition for successful evolution. However, in an industrialized human society, the growth of people's well-being is inseparably linked with the conscious restriction of the size of the family. This dependence in the middle of the last century was called the "demographic transition" (from traditional society to modern).
According to the popular "adaptive" theory, the demographic transition in the long run has a beneficial effect on evolutionary processes, since at a low birth rate the well-being of descendants increases, which ultimately must reach a level of wealth that allows more children in modern society.
Researchers from the London School of Hygiene and Tropical Medicine, University College London and Stockholm University do not agree with this theory. They confirm that a small number of children contribute to further economic success and the acquisition of high social status by descendants, but they say that their number is decreasing. Scientists conclude that the decision to limit the size of the family can contribute to improving the economic and social status of descendants, but socio-economic success does not always lead to success in the evolutionary.
The study emphasizes the conflict in modern society between socioeconomic and biological (evolutionary) success, whereas in traditional society behavior that leads to high social status and well-being, as a rule, also assumes large offspring.
Scientists used data on 14 thousand people who were born in Sweden at the beginning of the 20th century and all their offspring to this day for their research.
The researchers determined the social and economic success of these people with the help of indicators such as the success of schooling, the availability of higher education and the total income of families.
Reproductive success was determined by the number of people who survived to maturity, by marriage to 40 years and by the number of offspring until 2009.
It turned out that the smaller family size in the first generation under study and the smaller number of children in subsequent generations are indeed associated with the best socioeconomic status of descendants. However, contrary to the adaptive hypothesis, the small generation and high welfare of the family did not have any impact on the reproductive success of the following generations, or this influence was negative.