The average age of Swedish women having their first child has steadily increased, with more women over 45 becoming mothers than teenagers. In 2021, the average Swedish woman was 30.1 years old when she had her first child, while the average Swedish man was 32.1 years old. This pattern of men being older than women when having children is a global phenomenon, and researchers suggest that men have been becoming fathers later in life for hundreds of thousands of years.
Determining the age at which our ancestors became parents is difficult, but researchers have used genetic mutations to estimate the age at which humans throughout history have become parents. They found that the average age of becoming parents over the last 250,000 years is 26.9 years old, with men generally having children later than women. This could be due to biological factors or social pressures in patriarchal societies.
Overall, the average age at which women have their first child has increased over time, but not to the same extent as men. The reason for this could be a combination of biological factors and societal pressures.
The age at which Swedish women have their first child has increased steadily. This week the news came that there are now more 45+ women becoming mothers than teenagers. In 2021, the 30-year dike was blown up for the first time. This year, the average Swedish woman was 30.1 years old when she had her first child, according to Statistics Sweden. In the meantime, however, the fathers have also grown older. In the same year, the Swedish man was on average 32.1 years old when he had his first child. That is, on the dot two years older than the woman.
Sweden is not unique. That the man is usually older than the woman when having children is a pattern that exists throughout the world. Not only that. Now researchers can state that men became fathers later in life for hundreds of thousands of years. As long as we humans have existed.
To find out how old our ancestors were when they became parents is tricky. Especially if we want to look further back in history, because it doesn’t take many generations before the notes start to thin out and disappear completely.
The older the parents, the more mutations.
But inside our genetic mass there is another kind of documentation – in the form of genetic changes, or mutations. All children have mutations that their parents do not have. These changes occur when the genetic material inside the gametes (eggs or sperm) is damaged before fertilization or as random errors when the cells divide. On average, a person’s genome contains between 25 and 75 completely new mutations that their parents do not have.
Consequently, it is possible to compare parents and their children and classify the changes. That’s exactly what researchers did when they tracked new genetic changes in 1,500 Icelanders over three generations. The research, which was reported in the journal Nature in 2017, shows that the number of new mutations depends on how old the mother or father is at conception. The older the parents, the more mutations. Age also controls the type of mutations the child receives with distinct differences between the sexes of the parents.
Based on the Icelanders’ genome, researchers at Indiana University, Bloomington, USA, have developed software that can not only detect such changes, but also link them and their occurrence to the age and gender of the parents. Now the researchers have used this software on the sequenced genome of 2,500 living people from different parts of the world, in order to understand when different kinds of genetic changes appeared during human development.
The men have always had children later in life than the women.
In that way researchers have managed to estimate the average age at which we became parents throughout history. According to the researchers, who report their results in Science Advances, we have been 26.9 years old on average – during the last 250,000 years. That is, as long as we humans have existed. The age has varied over the millennia, but men have always had children later in life than women. Because according to the study, the woman was on average 23.2 years old when she became a parent, compared to the man’s 30.7 years.
Why this clear age difference, one might wonder.
A general explanation is of course that it is biologically possible. It may seem unfair, but at the age of 35 a woman’s fertility declines significantly, while men can often become fathers much later. In addition, population geneticist Mikkel Schierup speculates in Nature Briefing, social factors may have played a role. For example, if there was social pressure on men in patriarchal societies to first acquire status, before becoming fathers. Regardless, the average age at which women have children has increased over the past 5,000 years. Not close to the man’s, admittedly, but well to 26.4 years.