Back and Next - Back and NextCRA Chimpanzees support another international scientific paper
Monday, January 12, 2009
Only a month before her death Dr Stella Brewer Marsden OBE, of the Chimpanzee Rehabilitation Association (CRA), managed to have another peer reviewed scientific paper published.
Co-authored with Dr M Emery-Thompson, Dr J Goodall, Dr R Wrangham, et al, and titled: Aging and Fertility Patterns in Wild Chimpanzees Provide Insights into the Evolution of Menopause it appeared in Current Biology, Volume 17, Issue 24, 18 December 2007, Pages 2150-2156. Menopause is an interesting phenomenon, possibly limited to human primates, in that a large proportion of human females live decades beyond their reproductive life span.
It had been suggested that wild chimps might also live well beyond their reproductive years and either enter menopause or at least exhibit a significant decline in fertility in later years. The paper shows neither to be the case, with healthy females maintaining high birth rates into old age. The paper was based on demographic date from the CRA’s chimps (currently 81) living at the River Gambia National Park together with those from several other well studied chimpanzee sites across Africa.
But the paper did not touch on the ‘Why’ of menopause. Is the menopause phenomenon merely the result of increasing longevity and thus women out-living their egg supply - as well as out-living men? But where is the evolutionary advantage in that? Or did women actually evolve the grandmother function? As grandmothers they are around to help ensure that yet more of their genes survive, but this time indirectly by helping both their daughters and their grand-children to prosper.
The ‘Why’ question has been a matter of scientific debate for some time. Research undertaken earlier this decade in Finland showed the clear reproductive advantage for a daughter having her mother alive and living not far away. These daughters gave birth earlier and their inter-birth intervals (time between births) were shorter than those whose mother had died. The effects were reinforced when the matriarch lived less than 20 km away.
Very interesting was the fact that the average age at death of these post-menopausal matriarchs corresponded closely to the point at which their own daughters stopped reproducing. Once her daughter became unable to reproduce then the matriarch’s presence, in evolutionary reproductive terms, became redundant.
The debate goes on with a research paper very recently reported in New Scientist further supporting the evolutionary advantage deriving from the ‘grandmother hypothesis’. But whatever the final outcome of the debate, the demographic data collected on the CRA’s chimps in The Gambia will have played some small part.
Co-authored with Dr M Emery-Thompson, Dr J Goodall, Dr R Wrangham, et al, and titled: Aging and Fertility Patterns in Wild Chimpanzees Provide Insights into the Evolution of Menopause it appeared in Current Biology, Volume 17, Issue 24, 18 December 2007, Pages 2150-2156. Menopause is an interesting phenomenon, possibly limited to human primates, in that a large proportion of human females live decades beyond their reproductive life span.
It had been suggested that wild chimps might also live well beyond their reproductive years and either enter menopause or at least exhibit a significant decline in fertility in later years. The paper shows neither to be the case, with healthy females maintaining high birth rates into old age. The paper was based on demographic date from the CRA’s chimps (currently 81) living at the River Gambia National Park together with those from several other well studied chimpanzee sites across Africa.
But the paper did not touch on the ‘Why’ of menopause. Is the menopause phenomenon merely the result of increasing longevity and thus women out-living their egg supply - as well as out-living men? But where is the evolutionary advantage in that? Or did women actually evolve the grandmother function? As grandmothers they are around to help ensure that yet more of their genes survive, but this time indirectly by helping both their daughters and their grand-children to prosper.
The ‘Why’ question has been a matter of scientific debate for some time. Research undertaken earlier this decade in Finland showed the clear reproductive advantage for a daughter having her mother alive and living not far away. These daughters gave birth earlier and their inter-birth intervals (time between births) were shorter than those whose mother had died. The effects were reinforced when the matriarch lived less than 20 km away.
Very interesting was the fact that the average age at death of these post-menopausal matriarchs corresponded closely to the point at which their own daughters stopped reproducing. Once her daughter became unable to reproduce then the matriarch’s presence, in evolutionary reproductive terms, became redundant.
The debate goes on with a research paper very recently reported in New Scientist further supporting the evolutionary advantage deriving from the ‘grandmother hypothesis’. But whatever the final outcome of the debate, the demographic data collected on the CRA’s chimps in The Gambia will have played some small part.
Author: By Abdoulie John
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