Assumption of the grandmother

The assumption of the grandmother aims at explaining why the Ménopause occurred during the evolution of humanity, whereas it is rare at the Mammifère S, and how this unfertile age of the life could confer a real evolutionary advantage on the human ones. The menopause would originate in the risks associated with the Grossesse and the Accouchement as well as the relative importance attached to the parental investment by the mankind. The investment of the grandmothers would have also her importance at the rare animal species which know the menopause, as for example the Baleine S. This assumption is due to Kristen Hawkes and C.G. Williams, who was the first to be advanced that the menopause could have a protective effect.

The pregnancy as well as the childbirth are extremely prejudicial with the health of the women and their Longévité. The pregnancy increases their needs for heating consumption especially while the childbirth exposes them to infections mortals, when they are old. As certain anthropologists think as the old women of prehistoric times were less fertile than youngest.

One can imagine that, having lost their capacity of procreation, the old mothers laid out of more than time to help and protect their children and grandchildren and to deal with their education. The behaviorists qualify this investment of time of parental investment. The experiments and the simple observation showed that the animals having profited from such a period of protection and instruction were likely more to reach the age to which they were capable to reproduce.

At prehistoric times, the ménopausées women would thus have profited from increased average longevity a while laying out of more than time to deal with their children and their grandchildren. The offspring of these ménopausées women benefitted from this supplement of parental investment and was thus more likely to reach the age to procreate. Thanks to the embarrassments maternal of which she inherited, this new generation profited in its turn from the menopause and had a more posterity. Starting from this reasoning, the anthropologists stated an evolutionary theory of the menopause: among current women, the menopause would be the heritage of a protective adaptation which formerly made it possible to the old women to better concentrate their maternal resources.

This model was criticized in particular by J. Peccei, in particular because it is based on modern demographic data. According to this enquiring, the menopause would be a very old evolutionary advantage, selected in the young mothers so that they are invested in the follow-up of their offspring pre-adult. The age of the menopause would have then moved back with the lengthening of the average lifespan of the human being.

References

Alvarez, H.P., “Grandmother hypothesis and primate life histories”, American Newspaper off Physical Anthropology , Nov. 2000 113 (3): 435-50.
Lahdenper, Mr. Lummaa, V. and Russell, A.F. “Menopause: why does fertility end before life ? ”, Dec. 2004.
Peccei, J.S., “critical off the grandmother assumptions has: old and new”, American newspaper off human biology , July-August 2001, 13 (4): 434-52. (summary)

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