Granny - Mankind's Greatest Evolutionary Weapon

[jimmydasaint]

I always knew that my granny was a great benefit to society and especially my family However, I could not put this on a measurable footing with a sensible hypothesis. Much to my surprise, I found the following article which underlines the importance of genetically defined onset of menopause:

 

To determine the evolutionary significance of menopause, Daryl Shanley from the University of Newcastle in England, led a team that developed a computer model using historical demographic data from 5,500 people from two villages in Gambia. The model, detailed this week in the British journal, the Proceedings of the Royal Society B, used the data to project the nature of the population if women reached different ages of menopause.

 

The team's figures on population growth under various scenarios hinted that a woman undergoes menopause after 50 because she is at greater risk of dying in childbirth and consequently unable to provide care. The study also showed that toddlers' chances of survival are better with a maternal grandmother around. In other words, both the mother and the grandmother's input on child survival are factors in the evolution of menopause.

 

 

Cosmos

 

So it seems that the menopause has a possible purpose after all but that the granny is essential to the survival of the young generation.

 

Any thoughts?

Edited October 26, 2011 by jimmydasaint

[TonyMcC]

I have heard it suggested that the value of grandparents as back-up for parents in the event of the early death of a parent may have been, in historical times, a valuable factor in the survival of infants. I have also read that this might have been a factor in the evolution of a life form that commonly lives well beyond what is necessary for the safe maturing of offspring. These days it seems to be that "The Bank of Granny and Granddad" is a useful backup for "The bank of Mum and Dad" which seems to be essential for the development of the grandchildren - (rueful lol).

[jimmydasaint]

I have heard it suggested that the value of grandparents as back-up for parents in the event of the early death of a parent may have been, in historical times, a valuable factor in the survival of infants. I have also read that this might have been a factor in the evolution of a life form that commonly lives well beyond what is necessary for the safe maturing of offspring. These days it seems to be that "The Bank of Granny and Granddad" is a useful backup for "The bank of Mum and Dad" which seems to be essential for the development of the grandchildren - (rueful lol).

 

From the findings, it appears that the presence of a grandmother is a highly important factor in infant survival as you correctly mention, and that genes for menopause would have been preserved in an evolutionary sense for the purpose of increased survival advantage.

 

On a personal note, I would love to be a grandad at about 55 years old! It would be young enough to care and take part in the welfare of my grandchild, and old enough for a more mature world outlook.

 

The “grandmother hypothesis” proposes that menopause evolved because ancestral middle-aged women gained greater reproductive success from investing in extant genetic relatives than from continuing to reproduce [Williams GC. Pleiotropy, natural selection, and the evolution of senescence. Evolution 1957;11:398–411]. Because middle-aged women faced greater risks of maternal death during pregnancy and their offspring’s infancy than did younger women, offspring of middle-aged women may not have received the needed level of prolonged maternal investment to survive to reproductive age. I put forward the “absent father hypothesis” proposing that reduced paternal investment linked with increasing maternal age was an additional impetusfor the evolution of menopause. Reduced paternal investment was linked with increasing maternal age because men died at a younger age than their mates and because some men were increasingly likely to defect from their mateships as their mates aged. The absent father hypothesis is not an alternative to the grandmother hypothesis but rather a complement. It outlines an additional cost—reduced paternal investment—associated with continued reproduction by ancestral middle-aged women that could have been an additional impetus for the evolution of menopause. After reviewing additional explanations for the origin of menopause (“patriarch hypothesis,” “lifespan-artifact” hypotheses), I close by proposing a novel hypothesis for the ontogeny of menopause.

 

According to the “adaptive onset hypothesis,” the developmental timing of menopause is a conditional reproductive strategy in which a woman’s age at onset is influenced by the likelihood that any children she could produce would survive to reproductive age. Twelve variables predicted to be associated with age at onset and evidence that bears upon the predictions is discussed.

 

Link

Edited October 26, 2011 by jimmydasaint