The Average Age at Conception for Men & Women Over the Past 250,000 Years
The age gap between mothers and fathers has narrowed over the course of human evolution, according to evolutionary biologists.
A generation's lifespan can reveal a lot about the biology and social structure of humans. With a new technique they devised utilizing DNA mutations, researchers at Indiana University can now ascertain the typical age at which women and men gave birth throughout the course of human evolution. The study, which was released in Science Advances, claims that the average age at which humans gave birth to offspring over the past 250,000 years was 26.9.
The average age difference between fathers and mothers has also decreased over the previous 5,000 years, with women' ages now averaging 26.4 years according to the study's most current estimates. Moreover, fathers have consistently been older than mothers, who are on average 23.2 years old.
Mothers bearing children at older ages appears to be the main cause of the gap closing. The researchers discovered that parental age has not increased constantly over time, and may have even decreased around 10,000 years ago due to population growth occurring at the same time as the development of civilization, with the exception of the recent increase in mother age at childbirth.
The authors were able to do this by first identifying that about 25 to 75 new mutations are found in the DNA of children compared to the genomes of their parents. By comparing the DNA of the parents and the kids, researchers then identified the type of mutation that took place.
The authors discovered a pattern after studying the mutations in hundreds of offspring: the kind of mutations that children get depend on the parents' ages. The compounding effects of either recombination or mutation of modern human DNA sequence divergence from ancient samples were the foundation of earlier genetic methods for estimating historical generation duration. However, the results were averaged over the previous 40,000 to 45,000 years and included both males and females.
The authors created a model that uses de novo mutations, or genetic changes that occur for the first time in one family member as a result of a variation or mutation in a parent's germ cell or that develops in the fertilized egg during early embryogenesis, to estimate the male and female generation times at various points over the course of the past 250,000 years.
The initial goal of the study was to determine the number of mutations transferred from parents to children; it was not to explore the relationship between gender and age at conception throughout time. They only became aware of the age-based mutation patterns when attempting to comprehend how these patterns differ and overlap between humans and other species.
Our genes serve as a kind of manuscript for the history of human evolution. The results of the DNA research support certain information we already had from other sources, including the recent increase in parental age. This work can also benefit in our comprehension of the environmental difficulties that our ancestors faced as well as our ability to foresee how future environmental change will affect human communities.
Wang, R. J., Al-Saffar, S. I., Rogers, J., & Hahn, M. W. (2023). Human generation times across the past 250,000 years. Science Advances, 9(1), eabm7047. https://doi.org/10.1126/sciadv.abm7047