WEDNESDAY, March 10 (HealthDayNews) -- It was no accident if your grandmother helped raise you: It was a biological and social necessity that helped you survive and helped your mother have more children, researchers report. While most female animals continue to reproduce until they die, women live long after menopause. The evolutionary explanation may be the so-called "grandmother hypothesis." This hypothesis says that menopause and female life span beyond the ability to have children evolved because the advantage of helping daughters reproduce and raise their children outweighed the advantages of continuing to give birth. Latina Movies It suggests natural selection favored menopause, long life and perhaps even close family ties, because only grandmothers who are not busy feeding their own children have time to help with grandchildren. In a new study, researchers looked at two groups of women -- one in Finland and the other in Canada. In Finland, they collected data on 537 women, following the families from 1702 to 1823. Hornyspanish flies The Canadian population was made up of 3,290 women born from 1850 to 1879. The research team followed these families through over 130 years. In both groups they looked at the life span of the women, according to the report in the March 11 issue of Nature. MikeinBrazil "Surviving grandmothers may have some effect on the reproduction of their own children," says study co-author Marc Tremblay, director of the Interdisciplinary Research Group on Demographics, Epidemiology and Genetics at the University of Quebec. This influence is on the number of children that their own children have and how many survive to adulthood, he explains. 8th street movies "On average, in the families where the grandmother was still living when their children started to have children, there were more children born compared with families where the grandmother was dead," Tremblay says. Also, more children survived when the grandmother was around than when she wasn't, he adds.