Grandfathers' Role In Reproduction Unravelled By Researchers (7/29/2007)

Researchers at the University of Sheffield, in collaboration with the University of Turku in Finland, have discovered that grandfathers have little influence on the reproductive success of their adult children, where as grandmothers gain two extra grandchildren for every ten years they live after the menopause.

Unlike women who survive past menopause age, men living past the reproductive potential of their wife in a monogamous society brought little in the way of survival or reproductive benefits to their children. The study found that although all offspring began to have their own children two-and-a-half-years younger if their fathers were still alive, and also had shorter birth intervals between children, it was only the eldest son that benefited from the presence of the father in terms of increased family size.

Dr Virpi Lummaa and Dr Andrew Russell from the University of Sheffield´s Department of Animal and Plant Sciences, and Dr Lummaa´s PHD student, Mirkka Lahdenpera, from the University of Turku, used Finnish church records spanning from 1719 to 1839 as part of their research. The team examined the family histories of 361 men and their 2,227 offspring and the complete survival history of their 4,683 grandchildren to determine how having a grandfather alive affects the success of the family.

The researchers also found that unlike grandmothers, whose presence brought significant benefits to each grandchild´s survival chances to adulthood, having a grandfather around made no difference to the grandchild´s mortality risk.

Dr Lummaa said: "We have carried out previous research on the benefits of grandmothers but we wanted to get the full picture by looking at grandfathers as well. The results suggest the long lifespan in human men has not benefited their adult offspring´s reproductive success, even though grandfathers are much valued today. It is thus more likely that longevity in men is related to their ability to have their own offspring even at advanced ages."

Note: This story has been adapted from a news release issued by the University of Sheffield

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