Grannies can’t help but prefer their son’s daughters to their other grandchildren, according to a new study.
The researchers at Cambridge University, who also suggested that a son’s sons were least popular among grandmothers, believe granny’s favouritism is all down to DNA.
The laws of inheritance mean that of all their grandchildren, grannies are most genetically similar to their son’s daughters and least genetically similar to their son’s sons.
Grandmothers share about a quarter of their genes with each grandchild. However, the difference comes in the way the female X chromosome are passed through the generations, causing some grandchildren share more than a quarter.
Grannies pass about 31% of their genes to their son’s daughters, but only 23% to their son’s sons. Their daughter’s children fall in the middle, with both sexes sharing about 25% of their genes with their grandmothers.
The researchers also found that grandchildren may give off ‘signals’, perhaps in the form of smell or facial resemblance, that help grandmothers work out how similar they are genetically.
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