Although many factors influence the size of a family, Australian researchers have found that the genetic influences on both the number of children you have and the number of grandchildren you have are identical.
This suggests that the genes affecting the number of kids you have are the same as those which affect how many grandchildren you end up with.
Previous measures of reproductive fitness considered only the quantity of offspring, possibly neglecting variation in offspring reproductive quality that may influence the number of grandchildren.
To determine how genetic factors influence grandchildren quantity, Brendan Zietsch and colleagues at the School of Psychology, University of Queensland, traced the number of children and grandchildren born to Swedish twins who were themselves born between 1915 and 1929.
The researchers correlated the number of children of one twin with the number of grandchildren of the other twin.
The authors report this correlation was higher for identical twins than for non-identical twins, likely signifying overlapping genetic influences on the number of offspring and grandoffspring.
The article, “Perfect genetic correlation between number of offspring and grandoffspring in an industrialized human population”, was published by the Proceedings of the National Academy of Sciences in the USA.
It was written by Brendan Paul Zietsch, Ralf Kuja-Halkola, Hasse Walum, and Karin J.H. Verwejj.
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