Showing posts with label brave. Show all posts
Showing posts with label brave. Show all posts
Monday, March 24, 2014
Saturday, July 20, 2013
Sunday, June 16, 2013
Mate Choice and the Origin of Menopause
Mate Choice and the Origin of Menopause
Abstract
Human menopause is an unsolved evolutionary puzzle, and relationships among the factors that produced it remain understood poorly. Classic theory, involving a one-sex (female) model of human demography, suggests that genes imparting deleterious effects on post-reproductive survival will accumulate. Thus, a ‘death barrier’ should emerge beyond the maximum age for female reproduction. Under this scenario, few women would experience menopause (decreased fertility with continued survival) because few would survive much longer than they reproduced. However, no death barrier is observed in human populations. Subsequent theoretical research has shown that two-sex models, including male fertility at older ages, avoid the death barrier. Here we use a stochastic, two-sex computational model implemented by computer simulation to show how male mating preference for younger females could lead to the accumulation of mutations deleterious to female fertility and thus produce a menopausal period. Our model requires neither the initial assumption of a decline in older female fertility nor the effects of inclusive fitness through which older, non-reproducing women assist in the reproductive efforts of younger women. Our model helps to explain why such effects, observed in many societies, may be insufficient factors in elucidating the origin of menopause.Author Summary
The origin and evolution of menopause is understood poorly and explanations remain contentious. Virtually ignored among explanations is the effect that mate choice can exert on an evolving population. We designed and used a computational model and computer simulation to show that male mating preference for younger females in humans could have led to the accumulation of mutations deleterious to female fertility and thereby produced menopause. Our model demonstrates for the first time that neither an assumption of pre-existing diminished fertility in older women nor a requirement of benefits derived from older, non-reproducing women assisting younger women in rearing children is necessary to explain the origin of menopause.- wong chee tat :)
Study blames men for menopause
Study blames men for menopause
POSTED: 15 Jun 2013 7:44 AM
Men and their preference for younger female mates may have led to the phenomenon of menopause in women, according to a controversial study by Canadian researchers published this week.
WASHINGTON: Men and their preference for younger female mates may have led to the phenomenon of menopause in women, according to a controversial study by Canadian researchers published this week.
"If women were reproducing all along, and there were no preference against older women, women would be reproducing like men are for their whole lives," said evolutionary geneticist Rama Singh, a professor at McMaster University.
Singh said the conventional "grandmother theory," which holds that older women grow infertile so that they can assist the survival of their kin by helping to raise their children's offspring, did not make sense to him.
Instead of age leading to infertility, Singh theorised that the dwindling pool of male mates for older women - because many older men seek to mate with younger women - led to a lack of reproduction that gave rise to menopause.
His work, backed up by computer models, suggests that a male mating preference for younger females could have led to the accumulation of genetic mutations that would harm female fertility and bring on menopause.
The study was published on Thursday in the open-access, peer-reviewed journal PLOS Computational Biology.
But while the assertion raised many eyebrows, not all experts are convinced by Singh, who questioned why menopause appears to be mainly a human phenomenon.
"I cannot agree with the theory put forth," said Steven Goldstein, professor of obstetrics and gynaecology at New York University School of Medicine.
"There are other primates who do experience menopause, although life expectancy after menopause is extremely limited," said Goldstein, who was not involved in the research.
"The same was true of humans until roughly the 1850s. In 1850 the average age of menopause was 46 and life expectancy was 50, which more closely parallels that of chimpanzees or gorillas.
Rather, a more accurate explanation would be that scientific advances like water purification and antibiotics have led to much longer lives among humans, he said.
"The cessation of reproductive capabilities in higher primates has always come shortly before the life span ends. It is only the advances of modern society that have women living so very long," he told AFP.
- AFP/fl
- wong chee tat :)
POSTED: 15 Jun 2013 7:44 AM
Men and their preference for younger female mates may have led to the phenomenon of menopause in women, according to a controversial study by Canadian researchers published this week.
WASHINGTON: Men and their preference for younger female mates may have led to the phenomenon of menopause in women, according to a controversial study by Canadian researchers published this week.
"If women were reproducing all along, and there were no preference against older women, women would be reproducing like men are for their whole lives," said evolutionary geneticist Rama Singh, a professor at McMaster University.
Singh said the conventional "grandmother theory," which holds that older women grow infertile so that they can assist the survival of their kin by helping to raise their children's offspring, did not make sense to him.
Instead of age leading to infertility, Singh theorised that the dwindling pool of male mates for older women - because many older men seek to mate with younger women - led to a lack of reproduction that gave rise to menopause.
His work, backed up by computer models, suggests that a male mating preference for younger females could have led to the accumulation of genetic mutations that would harm female fertility and bring on menopause.
The study was published on Thursday in the open-access, peer-reviewed journal PLOS Computational Biology.
But while the assertion raised many eyebrows, not all experts are convinced by Singh, who questioned why menopause appears to be mainly a human phenomenon.
"I cannot agree with the theory put forth," said Steven Goldstein, professor of obstetrics and gynaecology at New York University School of Medicine.
"There are other primates who do experience menopause, although life expectancy after menopause is extremely limited," said Goldstein, who was not involved in the research.
"The same was true of humans until roughly the 1850s. In 1850 the average age of menopause was 46 and life expectancy was 50, which more closely parallels that of chimpanzees or gorillas.
Rather, a more accurate explanation would be that scientific advances like water purification and antibiotics have led to much longer lives among humans, he said.
"The cessation of reproductive capabilities in higher primates has always come shortly before the life span ends. It is only the advances of modern society that have women living so very long," he told AFP.
- AFP/fl
- wong chee tat :)
Monday, January 7, 2013
国大一名奖学金得主被指上载猥亵录像片段到互联网
Updated: Sunday, 06 January 2013 07:21
国大一名奖学金得主被指上载猥亵录像片段到互联网
新加坡国立大学的一名奖学金得主，被指上载猥亵录像片段到互联网，这名学生已经对此向警方报案。
较早前，本地报章报道，这名国大男生上载了长达14分钟的短片，裸露身体对着镜头手淫，而且还用尺量他的下体。
国大发言人答复本台的询问时说，这名学生告诉校方，短片中的人并不是他，而他在去年6月已经报警。
发言人也说，校方已经和男生面谈，发现没有证据断定录像中的人是这名学生。
国大也重申，校方不会纵容学生做出具冒犯的举动，并会对任何违反学生守则的人采取纪律行动。
- wong chee tat :)
国大一名奖学金得主被指上载猥亵录像片段到互联网
新加坡国立大学的一名奖学金得主，被指上载猥亵录像片段到互联网，这名学生已经对此向警方报案。
较早前，本地报章报道，这名国大男生上载了长达14分钟的短片，裸露身体对着镜头手淫，而且还用尺量他的下体。
国大发言人答复本台的询问时说，这名学生告诉校方，短片中的人并不是他，而他在去年6月已经报警。
发言人也说，校方已经和男生面谈，发现没有证据断定录像中的人是这名学生。
国大也重申，校方不会纵容学生做出具冒犯的举动，并会对任何违反学生守则的人采取纪律行动。
- wong chee tat :)
NUS student not involved in sex video, says university
NUS student not involved in sex video, says university
Posted: 05 January 2013 2149 hrs
SINGAPORE: The National University of Singapore (NUS) student that is supposedly linked to an online sex video has informed the university he is not the person featured in the video.
According to media reports, the video features a naked man masturbating and speaking to the camera.
An NUS spokesperson said the student in question made a police report in June 2012 on the matter.
The school said it has looked into the matter and interviewed the student.
It added that there was no evidence to conclude that the person featured in the video is the student involved.
In addition, NUS said it does not condone offensive or lewd behaviour by any member of its community.
It said any student found in breach of the University's Code of Student Conduct will be disciplined.
In October last year, ASEAN scholar and law undergraduate, Alvin Tan stirred controversy by posting on his blog photos and videos of him and his girlfriend having sex.
- CNA/xq
- wong chee tat :)
Posted: 05 January 2013 2149 hrs
SINGAPORE: The National University of Singapore (NUS) student that is supposedly linked to an online sex video has informed the university he is not the person featured in the video.
According to media reports, the video features a naked man masturbating and speaking to the camera.
An NUS spokesperson said the student in question made a police report in June 2012 on the matter.
The school said it has looked into the matter and interviewed the student.
It added that there was no evidence to conclude that the person featured in the video is the student involved.
In addition, NUS said it does not condone offensive or lewd behaviour by any member of its community.
It said any student found in breach of the University's Code of Student Conduct will be disciplined.
In October last year, ASEAN scholar and law undergraduate, Alvin Tan stirred controversy by posting on his blog photos and videos of him and his girlfriend having sex.
- CNA/xq
- wong chee tat :)
Thursday, August 9, 2012
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