Researchers from Indiana University can determine the average age that women and men had children throughout human evolutionary history using a newly developed method using DNA mutations.?
According to the study, the average age at which humans had children throughout the past 250,000 years is 26.9. Moreover, fathers were consistently older at 30.7 years on average compared to mothers who averaged at 23.2 years.
In the last five years, however, the age gap has considerably reduced, bringing the average material age to be around 26.4 years. This mainly is because the mothers are having children at older ages.?
What¡¯s surprising is that despite the material age increasing, parental age hasn¡¯t really budged -- it may have dipped around 10,000 years ago due to population growth coinciding with the rise of civilisation.
Children¡¯s DNA inherited from their parents contain around 25 to 75 new mutations that allow scientists to compare the parents and offspring and then classify the kind of mutation that occurred. When looking at mutations in thousands of children, researchers spotted a pattern -- the type of mutations kids get is based on the ages of the mother and the father.
Earlier genetic approaches to finding historical generation times were based on the compounding effects of either recombination or mutation of modern human DNA sequence divergence from ancient samples. However, the results were averaged across both males and females and across the past 40,000 to 45,000 years.?
Researchers Richard Wang and Matthew Hahn and their colleagues developed a model that makes use of de novo mutations -- a kind of mutation that's present for the first time in a family member as a result of a variant or mutation in a germ cell of one of the parents or if it surfaces in the fertilised egg during embryogenesis -- to separately predict the male and female generation times at several different points throughout the past 250,000 years.
Researchers weren¡¯t really seeking to understand the relationship of gender and age at conception over time, they were conducting a broader investigation into the number of mutations passed from parents to children.
They only saw the age-based mutation patterns when looking to understand similarities in these patterns between mammals and humans.?
Wang explains, ¡°The story of human history is pieced together from various sources: written records, archaeological findings, fossils, etc. Our genomes, the DNA found in every one of our cells, offer a kind of manuscript of human evolutionary history. The findings from our genetic analysis confirm some things we knew from other sources (such as the recent rise in parental age), but also offer a richer understanding of the demography of ancient humans. These findings contribute to a better understanding of our shared history.¡±
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