Scientists have discovered a new way to identify the average ages at which men and women reproduced throughout their lives. human evolutionary history.
By studying DNA mutations in modern humans, they discovered a window that allowed them to look back 250,000 years in time.
“Through our research in modern humans, we noticed that we could predict the age at which people had children based on the types of DNA mutations they left behind in their children.” He says study co-author Matthew Hahn, a geonomicsist at Indiana University Bloomington.
“We then applied this model to our human ancestors to determine at what age our ancestors procreated.”
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 It’s also around the time our species first appeared.)
Average Homo sapiens father has always been older than average Homo sapiens mother, found the study, with men who become fathers at 30.7 years, compared to 23.2 years for women.
But the age difference has narrowed over the past 5,000 years, the researchers add, noting that the most recent estimates from the study suggest that the average age when women become parents he is now 28 years old. This trend seems largely driven by women having children at later ages, they suggest.
Apart from the recent increasing maternal ageHowever, the study found a remarkable consistency in the average age of new parents throughout the existence of our species. It has not increased steadily since prehistoric times, the team reports, although it has fluctuated over time.
The average age of conception appears to have fallen by 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 could be related to rapid population growth at that time.
Recorded history only goes back a few thousand years at best, and broad population-level information like this is difficult to obtain from archaeological evidence alone.
But secrets of our ancestors they also lurk within each of us today, which is how Hahn and his colleagues stumbled upon a way to determine the age of parents so far back in time.
The new study takes advantage of the discovery about de novo mutations: DNA alterations that debut in a family member and appear spontaneously instead of being inherited through the family tree.
While working on another project related to 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 novel mutations formed in parents before being passed on to their children depends on each parent’s age of conception.
This allowed the researchers to estimate separate male and female generation times over 250,000 years.
“These mutations from the past accumulate with each generation and exist in humans today.” He says Study co-author and Indiana University phylogeneticist Richard Wang.
“Now we can identify these mutations, see how they differ between male and female parents, and how they change based on the age of the parents.”
Previous research has also used genetic clues to estimate generation length over time, but has generally relied on comparisons between modern DNA and ancient samples that were averaged between sexes and over the past 40,000 to 45,000 years, the researchers note. .
“Human history is made up of a diverse set of sources: written records, archaeological finds, fossils, etc.” Wang He says.
“Our genomes, the DNA found in each 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, but also offer a richer understanding of the demographics of ancient humans.”
The study was published in Progress of science.
