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crazy distaff chimpanzees in Uganda live well past the point when they can reproduce and belike go through menopause similar to humans , a new subject area has launch . The determination upgrade fresh doubtfulness about why human feel menopause .
Until now , human were one of only three animal speciesknown to go through menopause — along with orcas ( Orcinus sea wolf ) and short - finned pilot whales ( Globicephala macrorhynchus ) . homo were thought to be the only primates that do n’t remain fertile for their entire lives .
Chimpanzees (Pan troglodytes schweinfurthii) at Kibale National Park in Uganda.
" How this life sentence history evolved in humans is a enthralling yet challenging puzzle , " study lead authorBrian Wood , an comrade prof and evolutionary anthropologist at the University of California Los Angeles , tell in astatement .
That ’s because the inability to reproduce past a certain age has no obvious evolutionary advantage . To explain it , researchers have previously posited that postmenopausal people may bet an important function in caring for their children ’s children and boosting their endurance chances , helping to ensure that their genes will be passed on — an estimate known as the " grandmother theory . "
To find out whether climacteric occurs in other primates , the source of a subject put out Thursday ( Oct. 26 ) in the journalScienceinvestigated the richness of some of our unaired living relatives — easterly chimpanzee ( Pan troglodytes schweinfurthii ) .
A female chimpanzee from the Ngogo community in western Uganda.
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Grant Wood and his colleagues pored over 21 year ' Charles Frederick Worth of demographic and fertility data pull in between 1995 and 2016 in Uganda ’s Kibale National Park , where the Ngogo community of wild chimpanzees lives . The researcher analyzed records for 185 distaff chimp . They regain a decline in fertility from the age of 30 onward and no births after 50 , despite several females live long past that point
It turns out that Ngogo female Pan troglodytes spend one - fifth of their grownup lives in a " post - procreative state " — around half the proportion figure for modern human hunter - accumulator , such as the Hadza people . Urine sample take from 66 female Pan troglodytes in unlike reproductive phase ( ages 14 to 67 ) also revealed hormonal change as they get elderly and stopped get baby — similar to those seen in man going through climacteric .
Female chimpanzees in Uganda’s Ngogo community experienced a menopausal transition similar to women.
But unlike many humanity , distaff chimpanzees do n’t stay with their original kindred to reproduce and instead disperse to other groups , go away behind their aging mother . The grandmother hypothesis therefore has no legs to stand on in chimpanzees .
Instead , " the results show that under certain ecological term , menopause and post - prolific survival can emerge within a societal system that ’s quite unlike our own and include no grandparental backing , " Sir Henry Joseph Wood say .
While the new determination in chimps does n’t decree out the grandmother hypothesis applying to humans , it stir enquiry about menopause ’s origins in our species .
Chimpanzees and humans may have inherited gene inscribing menopause from a coarse ancestor , according to the study . instead , the trait may have evolve independently in each specie .
If that ’s the case , the novel study provides " a solid basis for considering the role that ameliorate diet and lowered peril of depredation would have played " in the organic evolution of menopause in humans , Wood say .
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That ’s because chimpanzee in Kibale National Park have never had it so good . hunter wiped out their only marauder , leopards , in the sixties , and humankind no longer wipe out the Pan troglodytes either . Ngogo chimpanzees also have plenty of yield and consume more meat than neighboring chimp communities , the researchers compose in the study .
This salutary life might explain why female chimpanzees there live long past their fertile old age . Although non - procreative female exist in other groundless Pan troglodytes residential area , only a few have lived beyond the geezerhood of 50 , according to the study .
It ’s ill-defined whether the mansion of menopause detected in chimps rise entirely from " remarkably favourable ecological shape " or the apes evolved that agency . late environmental changes and disease epidemic shortening their lifespan spans may have , until now , delete the grounds of an evolutionary chronicle that includes change of life , consort to the written report .
