By | November 24, 2022
Fathers have been older than mothers by 250,000 years, the study shows

Scientists have discovered a new way to identify the middle age when men and women reproduced all the time human evolutionary history.

By studying DNA mutations in modern humans, they discovered a window that allowed them to look back 250,000 years.

“Through our research on modern humans, we noticed that we could predict the age at which people had children based on the types of DNA mutations they passed on to their children.” says study co-author Matthew Hahn, a genomicist at Indiana University Bloomington.

“We then applied this model to our human ancestors to determine the age at which our ancestors reproduced.”

They found that over the past 250,000 years, the average age for humans to have children is 26.9 years. (For context, 300,000 years ago is also about when our species first appeared.)

The average Homo sapiens dad has always been older than average Homo sapiens mother, the study found, with men become parents at 30.7 years, compared to 23.2 years for women.

But the age gap has narrowed over the past 5,000 years, the researchers add, noting the study’s latest estimates suggest the average age when women become parents is now 28 years old. This trend appears to be largely driven by women having children at older ages, they suggest.

Apart from the latest increasing maternal age, however, the study found remarkable consistency in the average age of new parents throughout our species’ existence. It hasn’t increased steadily since prehistory, the team reports, although it has fluctuated over time.

The average age at conception appears to have dropped about 10,000 years ago, and since that would roughly coincide with the advent of agriculture and the dawn of civilization, the researchers say it may be related to the rapid population growth at the time.

Recorded history stretches back only a few thousand years at best, and broad population-level information like this is difficult to glean from archaeological evidence alone.

But secrets of our ancestors also lurks within each of us today, and that’s how Hahn and his colleagues stumbled upon a way to determine the age of parents so far back in time.

The new study addresses the discovery of de novo mutations — DNA changes that debut in a family member, appearing spontaneously rather than being inherited through the family tree.

While working on another project involving these new genetic changes and parents of known agesthe researchers noticed an interesting pattern. Based on data from thousands of children, the pattern and number of new mutations that form in parents before being passed on to their children depends on each parent’s age at conception.

This allows the researchers to estimate separate male and female generation times over 250,000 years.

“These mutations from the past accumulate with each generation and are found in humans today,” says study co-author and Indiana University phylogeneticist Richard Wang.

“We can now identify these mutations, see how they differ between male and female parents, and how they change as a function of parental age.”

Previous research has also used genetic clues to estimate generation span over time, but it has typically relied on comparisons between modern DNA and ancient samples averaged across sexes and over the past 40,000 to 45,000 years, the researchers note.

“The story of human history is compiled from a variety of sources: written documents, archaeological finds, fossils, etc.,” Wang says.

“Our genome, the DNA found in all our cells, offers a kind of manuscript of human evolutionary history.

“The findings from our genetic analysis confirm some things we knew from other sources, but also provide a richer understanding of ancient human demography.”

The study was published in The progress of science.

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