Researchers at Indiana University in Bloomington, Indiana, used genetic changes in current human DNA sequences to pinpoint when men and women first started having children throughout the previous 250,000 years, or since the emergence of our species.
They developed a model to accomplish that using data monitoring the age of conception and DNA alterations through three generations of 1,500 Icelanders and their parents. To generate a history of motherhood and paternity over the years, they first used this model to sample 2,500 current people living all over the world. They then dated back to the development of various mutations.
"Through our research on modern humans, we noticed that we could predict the age at which people had children from the types of DNA mutations they left to their children," says study co-author Matthew Hahn, a genomicist at Indiana University Bloomington.
They discovered that across the centuries, dads were on average a lot older than moms: males became parents at 30.7 years old, whilst ladies became parents at 23.2 years old. That means that historically, males experienced fatherhood seven years later than women did, which is astounding.
According to earlier research, men have traditionally had children later than women, but those studies' estimations only covered the last 40,000 years. It is difficult to determine at what age people gave birth in the ancient past, but mutations that happen naturally between generations provide scientists with a method to trace back that information.
The study discovered remarkable constancy in the average age of new parents across the course of our species' history, with the exception of the recent increase in maternal age. The team notes that although it has changed throughout time, the rate of rise has not been constant since prehistory.
Since the development of agriculture and the beginning of civilization appear to have occurred around 10,000 years ago, the researchers speculate that the time's rapid population expansion may have caused the decline in the average age at conception.
Recorded history only spans a few thousand years at most, and it is challenging to infer large, population-level information like this just from archaeological findings.
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