According to recent studies, genetic inheritance accounts for 20 to 40 percent of a child's intelligence. (Photo: GT/Li Hao)
Do children inherit specific genetic traits from their mothers and others from their fathers?
Is a child's intelligence inherited primarily from his or her mother?
Many in China are pondering the question after a short Sina Weibo article was posted last week asserting that a mother's genetic makeup had three times as much influence in determining a child's intelligence as a father's.
"To know whether a son will be intelligent or not, one need only look to the mother," the article reads. "For men who consider themselves unintelligent, it is essential they find themselves a smart wife."
The article, which has since been forwarded more than 1.1 million times, also claims a child's personality and height are primarily inherited from the father.
The explanation given is that the genes that determine intelligence are located in the X chromosome, inherited mainly from a child's mother. As for personality and height, the article does not provide any reasoning. The article does not cite any scientific studies or provide any sources for any of its claims.
Si Dayong, a professor of evolution at Jilin University, rejected the assertions made in the Weibo article outright. "Sex-specific inheritance has little to do with X and Y chromosomes, but a kind of epigenetic inheritance [traits that are not caused by changes in the DNA sequence, but changes in gene expression]," he said "I have not found any particular traits that are inherited more from one's mother or father."
Inherited intelligence
A study that appeared in academic journal Behavior Science in 1982 looking at parent-offspring correlations for IQ noted that the correlation between a mother's intelligence and a child's intelligence was slightly higher at 0.464 than that of a father and a child at 0.423.
"I don't think this slight difference is statistically significant," said Si. "After all, genetic inheritance is random and complicated beyond human imagination."
While it has long been accepted that heredity plays a part in determining a child's intelligence, recent studies have suggested that it has less of a role than previously thought.
A 2013 study conducted by researchers from the University of Queensland analyzing DNA and IQ test results of more than 18,000 children from Australia, the Netherlands, the UK and the US found that heredity accounted for 20 to 40 percent of variation of childhood IQ, which is lower than the 40 to 50 percent estimated by earlier research.
Researchers further concluded that there was no single gene variant that could strongly predict childhood intelligence, and that genetically inherited intelligence was the cumulative effect of many different genes.
Zhao Bowen, a researcher at Shenzhen Huada Gene Research Institute, elaborated on the findings in an article on knowgene.com in 2014.
"Presently, no DNA site directly deciding human intelligence has been found," he said. "Parents' genetic influence on a child's intelligence is more or less even, and a child's intelligence tends to belong to a normal distribution curve, with the average of both parents' intelligence level as the median."
