Washington, Jan 23 : A new study has revealed that mothers are opting to have fewer kids in order to give them the best start in life, but by doing so they are going against millenia of human evolution.
For the study, Duncan Gillespie, Dr Virpi Lummaa and Dr Andrew Russell, from the University of Sheffield, analyzed Finnish church records from the 18th and 19th centuries and traced the reproductive histories of 437 women, their 2888 children and 6470 grandchildren.
The researchers found that fertility of kids from large poor families appeared to be constrained, potentially due to a lack of wealth and resources.
On the other hand, kids from large wealthy families went on to have large families themselves.
According to the study, this has caused a trade-off between offspring quantity and quality with modern women choosing to have fewer kids so that they can instead invest in their education or career, gaining resources to give their children the best start in life. esides this, the researchers found evidence for an evolved relationship between a mother's fertility and the fertility of her kids - the more offspring a woman has, the larger her overall family will be.
This means that women having fewer kids will ultimately have fewer grandchildren.
"Before modern day birth control high fertility was a sign of wealth and families would therefore strive to have large numbers of children. However for poor mothers, having more children did not always lead to more grandchildren, due to economic constraints on their children's fertility," Gillespie said.
"In today's society, this has gone even further with wealthy families choosing to invest in fewer children as well. However, this trade-off between offspring quantity and quality has come full circle in that fewer children will ultimately lead to smaller families. This could help explain the decline in fertility in modern society," Gillespie added.
The study has been published in Proceedings of the Royal Society B.