Researchers recently discovered 12 areas of the human DNA sequence that determine the age a person will have their first child, as well as the total number of children they will have over the course of a lifetime.
The study, published in Nature Genetics, was co-authored by 250 biologists, geneticists and sociologists from around the world, and was led by the University of Oxford.
The researchers analyzed 62 datasets with information from 238,064 men and women documenting the age that they had their first child, as well as information from 330,000 men and women documenting the number of children they had.
From this analysis, the researchers were able to identify the 12 areas of DNA that most directly impacted the age that people have their firstborn children and the number of offspring they will have. This comes in direct contention with the previous idea that reproductive behavior was a result of environmental and social factors and personal choices.
The 12 areas of human DNA were also found to be linked to other reproductive and sexual characteristics. These characteristics include the age at which a boy’s voice first cracks, the age in which girls begin to get their periods and the age in which a woman experiences menopause. The study’s authors believe that insight into these 12 areas of DNA can lead to greater breakthroughs on women’s fertility and the latest age a person can wait until having a child.
“For the first time, we now know where to find the DNA areas linked to reproductive behavior,” said Melinda Mills, the study’s lead author. “We found that women with DNA variants for postponing parenthood also have bits of DNA code associated with later onset of menstruation and later menopause.
One day it may be possible to use this information so doctors can answer the important question: ‘How late can you wait [to have a child]?’ based on the DNA variants.”
Although the researchers calculated that the combined DNA variants predicted less than 1 percent of the timing of a person’s firstborn child, the combined variants can predict in some cases whether a woman will remain childless.
“Our genes do not determine our behavior, but for the first time, we have identified parts of the DNA code that influence it. This is another small piece to understanding this very large jigsaw puzzle,” said study author Nicola Barban.
Within the 12 DNA regions, researchers identified 24 genes that are most likely responsible for the effects these regions have on reproductive behavior.
The researchers posit in the study’s conclusion that their findings can be beneficial in discovering how postponing reproduction into older age can be detrimental for some people, as well as further clarifying how long and to what age humans can wait to reproduce.